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PEACTICAL LOGIC; 
 
 OR, THE 
 
 ART OF THINKING. 
 
 p 
 
 BY 
 
 D. S. GREGORY, D.D., 
 
 PRESIOENT OF LAKE FOREST UNIVERSITY. 
 
 
 Philadelphia: 
 
 Eldredge & Brother, 
 
 No. 17 North Seventh Street. 
 1881. 
 

 TffI UBRAETl 
 OF C ONOR EMj 
 
 washimotm] 
 
 t^ 
 
 -*a^)^ 
 
 Entered, according to Act of Congress, in the year 1881, by 
 ELDREDGE & BROTHER, 
 
 -m 
 
 In the Office of the Librarian of Congress, at Washington. ^ 
 
 V%^ W^S® *&*k 
 
 J. FAGAN & SON, - 'f^a^* 
 
 ELECTROTYPERS, PHILAtfA. ^/jp^^ 
 
 ^ 
 
 CAXTON PRESS OF 
 SHEBMAN <& CO., PHILADELPHIA* 
 
PREFACE. 
 
 <»©<o 
 
 "VTEXT to right and noble living, which is the highest thing 
 -L^ to which man may aspire, may be placed the right think- 
 ing which is essential to such living. Logic, as the Science 
 of the Laws of Thought, is very widely studied, in the higher 
 schools, as an aid to the pupil in thinking ; yet it is the set- 
 tled conviction of many of the best educators that this Sci- 
 ence, as it is ordinarily presented, does very little toward 
 training to think or preparing for thinking. In short, there 
 seems to be a growing feeling that it rather serves, in case 
 of the average mind, to cram the memory and paralyze the 
 thinking powers. The author of this volume shares to some 
 extent in this conviction and feeling; hence the present 
 attempt to construct a Practical Logic, by the use of which 
 intelligent teachers may train inquiring minds to correct 
 thinking. 
 
 The only way to learn to think is by thinking; the only 
 way of training a pupil to think is by making him practise 
 thinking. Assuming the correctness of this principle, Logi- 
 cal Praxis is made the prominent and essential feature of 
 the work. Each principle of thought is turned into a Eule, 
 
 m 
 
IV PREFACE. 
 
 and then made part of the mental property and power of the 
 student by abundant exercises. 
 
 The best training in thinking must be intelligent and sys- 
 tematic. Accordingly the foundation for this is laid by a 
 comprehensive and systematic presentation of the forms and 
 laws of thinking. The processes of formation and unfolding, 
 of involution and evolution, are presented in succession. Be- 
 ginning with the simplest process of observation, the praxis 
 is carried, by successive stages, up to the highest and most 
 complex processes of constructive thinking, and the mind 
 capable of such work trained intelligently and systematically 
 to clear, distinct, connected, continuous, and constructive 
 thought. 
 
 To the various writers on the subject of Logic, the author 
 would acknowledge his indebtedness, and especially to Ueber- 
 weg, Hamilton, Thomson, Whately, Mill, Jevons, Atwater, 
 McCosh, Davis, Bowen, and Day. 
 
 To teachers he would suggest that Part I. may be used 
 
 in the earlier stages of training, and the remaining parts 
 
 reserved for a later stage. In the use of the text-book 
 
 the teacher will ordinarily do his best work for his pupil by 
 
 drawing largely on his own resources for material for praxis. 
 
 Each locality, school-room, branch of study, and experience 
 
 will suggest innumerable topics of fresh and living interest, 
 
 which may be profitably substituted for those given in the 
 
 text-book. 
 
 D. S. Gregory. 
 
 Lake Forest University, | 
 Lake Forest, III., August, 1881. J 
 
INTRODUCTION. 
 
 PAGE 
 
 I.— Nature of Logic 9 
 
 Topic 1. — Object-Matter of Logic 10 
 
 Topic 2. — Practical Aim of Logic 13 
 
 Topic 3. — Principles or Laws of Thought . . .17 
 II.— Divisions of Logic 22 
 
 PART I. 
 
 The Logic of Conception or the Teim. 
 
 CHAPTER I. 
 THE FORMATION OF CONCEPTIONS . . 25 
 
 Section I. — Observation 26 
 
 Topic 1. — The Predicables or Things Know able . 27 
 Topic 2. — Observation of Things Predicable . . 30 
 
 Section II.— Conception Proper 34 
 
 Topic 1. — Process of Concept-Forming . . . .34 
 Topic 2. — Product of Concept-Forming. . . . 38 
 
 Section III. — Classification 41 
 
 Topic 1. — Process of Classification . . . .41 
 Topic 2. — Eesults of Classification .... 44 
 
 Section IY.— Denomination or ^a^clng . .49 
 
 Topic 1. — Process of Naming 49 
 
 Topic 2. — Products of Najviing 52 
 
 1* v 
 
VI 
 
 CONTENTS. 
 
 CHAPTER II. 
 
 PAGE 
 
 THE UNFOLDING OF CONCEPTIONS . . 56 
 
 Section I.— Logical Partition 57 
 
 Topic 1. — Forms of Logical Partition . . . .59 
 Topic 2. — Rules of Logical Partition . . . .60 
 
 Section II.— Logical Division 64 
 
 Topic 1. — Forms of Logical Division . . . .65 
 Topic 2. — Rules of Logical Division . . . .68 
 
 Section III.— Logical Definition 75 
 
 Topic 1. — Kinds of Definition 75 
 
 Topic 2. — Rules of Logical Definition . . .81 
 
 PART II. 
 
 The Logic of Judgment or the Proposition. 
 
 CHAPTER I. 
 
 THE FORMATION OF JUDGMENTS OR PROP- 
 OSITIONS . . . . .93 
 
 Section I.— Process of Judgment-Forming . . 93 
 Topic 1. — The Elements of Judgment . . . .93 
 Topic 2. — Verification or Proof of Judgments . . 98 
 
 Section II.— Products of Judgment . . . .110 
 
 Topic 1. — Quality of Judgments Ill 
 
 Topic 2. — Quantity of Judgments 112 
 
 Topic 3. — Relation of Judgments 116 
 
 Topic 4. — Grammatical Combination of Judgments . 118 
 
 CHAPTER II. 
 THE UNFOLDING OF JUDGMENTS. . . 121 
 
 Section I.— Development of Contained Judg- 
 ments 121 
 
 Section II.— Development of Implied Judgments 123 
 Topic 1. — Simpler Forms of Implication . . . 123 
 Topic 2.---Obversion 123 
 
CONTENTS. 
 
 VT1 
 
 Section III.— Development of Inferred Judg- 
 ments 125 
 
 Topic 1. — Inferred Judgments by Additions . . 126 
 Topic 2. — Inferred Judgments by Disjunction . . 126 
 Topic 3. — Inferred Judgments by Conversion . . 126 
 Topic 4. — Inferred Judgments by Opposition . . 128 
 
 oX*o 
 
 PART III. 
 
 The Logic of Reasoning or the Syllogism. 
 
 CHAPTER L 
 
 THE FORMATION OF REASONING OR MEDI- 
 ATE INFERENCES . . . .135 
 
 Section I.— Process of Reasoning in General . 135 
 
 Topic 1. — Forms of Reasoning 135 
 
 Topic 2. — Elements of Reasoning 137 
 
 Topic 3. — Finding and Verifying Arguments . . 139 
 
 Section II.— Deductive Reasoning . . . .139 
 Topic 1. — Process of Verifying the Argument in De- 
 duction 139 
 
 Topic 2. — Products of Deductive Reasoning . . 141 
 
 Section III.— Inductive Reasoning . . . .147 
 Topic 1. — Verifying Cause in Induction . . . 147 
 Topic 2. — Products of Inductive Reasoning . . 157 
 
 CHAPTER II. 
 
 THE UNFOLDING OF REASONING OR THE 
 
 SYLLOGISM 162 
 
 Section I.— The Categorical Syllogism Unfolded 162 
 Topic 1. — Possible Forms or Figure and Mood . . 162 
 
 Topic 2. — Testing of Valid Forms 164 
 
 Topic 3. — Complex and Abnormal Forms . . . 179 
 Section II.— The Hypothetical Syllogism Un- 
 folded 185 
 
 Topic 1. — Conditional or Conjunctive Syllogism . 185 
 
Vlll CONTENTS. 
 
 PAGE 
 
 Topic 2. — Disjunctive Syllogism 188 
 
 Topic 3. — Dilemmatic Syllogism 189 
 
 Section III.— Conspectus of Fallacies . . .191 
 
 Topic 1. — Fallacies in Induction 191 
 
 Topic 2.— Fallacies in Deduction 192 
 
 PART IV. 
 
 The Logic of Construction or the System. 
 
 CHAPTER I. 
 
 THE FORMATION OF CONSTRUCTION OR 
 
 SYSTEM 200 
 
 Section I.— Scientific Construction . . . .200 
 Topic 1. — Process of Forming and Verifying Scien- 
 tific System 200 
 
 Topic 2. — Products of Scientific Construction . . 202 
 
 Section II.— Practical Construction . . .206 
 Topic 1. — Process of Forming and Verifying Prac- 
 tical System 206 
 
 Topic 2. — Products of Practical Construction . . 207 
 
 CHAPTER II. 
 THE UNFOLDING AND TESTING OF SYSTEMS. 207 
 
 Section I.— Ascertaining the Elements. . . 208 
 Topic 1. — The Whole and its Principle . . . 208 
 Topic 2. — The Articulation or Eelation of the Parts 209 
 Topic 3. — The Relation to the Objective Reality . 209 
 
 Section II.— Testing of Systems 210 
 
 Topic 1. — Directions for Testing 210 
 
 Topic 2.— Examples Illustrative 211 
 
 INDEX 213 
 
Practical Logic. 
 
 Introduction. 
 
 I. THE NATURE OF LOGIC. 
 
 What is Logic? — This question has been variously 
 answered. Whately says it may be considered as c< the 
 Science and also as the Art of Eeasoning." Hamilton de- 
 fines it as " the Science of the formal and necessary Laws 
 of Thought as Thought." Dr. Watts called his work, " The 
 Art of Thinking." According to his view, " Logic is the 
 art of directing the reason aright in acquiring the knowl- 
 edge of things, for the instruction both of ourselves and 
 others." 
 
 Without stopping to discuss these definitions, which would be un- 
 intelligible to the ordinary student at the outset, it is clear that these 
 different authors must either be defining different things, or defining 
 the same thing from different points of view, or defining different 
 things from different points of view. "Reasoning" and "thought" 
 are different things, the former being only one form of the latter. 
 The points of view of science and art are different, the one being 
 theoretical, the other practical. 
 
 Definition. — As treated in the present work, Logic is the 
 
 9 
 
10 PRACTICAL LOGIC. 
 
 Practical Science of the Principles or Laws which govern 
 the various forms of correct Thinking or Thought. 
 
 This definition will be best explained by considering the 
 following Topics : 
 
 Topio I,— The Object-Matter of Logic. 
 Topic II.— The Practical Aim of Logic. 
 Topic III.— The Principles or Laws of Thinking or Thought. 
 
 Topic First. — The Object-Matter of Logic is found in 
 the Forms of Thinking or Thought. 
 
 1. What is Thinking or Thought ? 
 
 (1.) In a loose sense, any operation of the human soul is 
 sometimes spoken of as thought. The man knows, feels and 
 purposes or wills ; any act of knowing, feeling, or willing 
 may, in this loose sense, be called thinking. The term is 
 evidently not used in this loose sense in the definition of 
 Logic. 
 
 (2.) In a stricter sense, thinking or thought is confined 
 to the operations of the intellect or power of knowing. 
 In popular phrase, it is any act of the head as distinguished 
 from the heart and will of the man. In this sense, " think- 
 ing " is synonymous with " knowing." 
 
 The main office of the human intellect is to know, i. e., first, to 
 apprehend objects in themselves and their phenomena or attributes; 
 and secondly, to apprehend objects or their phenomena in their con- 
 nections or relations. The first of these forms may be termed simple 
 apprehension, or intuition, or simple knowledge ; the second, thought- 
 knowledge, or thought. Logic has to do with thought-knowledge, or 
 thought. 
 
 To state the same thing in another and fuller form, the cognitive 
 power or intellect of man performs its entire office of knowing in 
 four different ways ; in other words, it has four different faculties : 
 
 1st. The intellect acquires the fundamental facts of knowledge of 
 things material and spiritual by the senses and consciousness ; and 
 has, therefore, a simple cognitive faculty. Its office is to gather the 
 material for the use of the higher faculties of thought. 
 
THE NATURE OF LOGIC. 11 
 
 2d. The intellect keeps the acquired knowledge in such shape as to 
 be able to reproduce it for use at any time when it may be needed by 
 the higher faculties ; and has, therefore, a conservative faculty or 
 memory. 
 
 These two faculties furnish knowledge and keep it at command for use, 
 and their operations are often spoken of, in a loose sense, as thought ; 
 but, using thought in the strict sense, it is often truly said of one who 
 uses these two powers with great ease, " He never had a thought in 
 his life. He is a mere man of memory.' 7 
 
 3d. The intellect compares the knowledges acquired and conserved, 
 and connects them into conceptions, judgments, and arguments ; and 
 has, therefore, a comparative, or elaborative, faculty. 
 
 4th. The intellect groups in systems, according to the law of the 
 true, the beautiful, or the good, the knowledges acquired by the simple 
 cognitive faculty, kept and reproduced by the conservative faculty, 
 and connected in thought by the comparative faculty ; and has, there- 
 fore, a system-making, or constructive, faculty. This is also discursive. 
 
 The term " thinking" or " thought " is often applied to all four forms 
 of intellectual action. This is evidently not the sense in which it is 
 used in the definition of Logic. 
 
 (3.) Thought or thinking, strictly speaking, is the opera- 
 tion or product of the operation of the third and fourth fac- 
 ulties only, i. e., of the comparative and constructive facul- 
 ties only. These faculties are the thought faculties ; their 
 operation is thinking ; and the product of their operation is 
 thought. Ordinarily, the word thought is used for any or 
 all three : the faculty, its exercise, its product. These fac- 
 ulties are also called discursive, since they proceed from 
 simple knowledges to new results founded upon them. 
 
 2. What are the Forms of Thinking or Thought ? 
 
 The forms of thinking or thought are the forms in which 
 the discursive or thought faculties act, or the products of 
 that action. 
 
 (1.) As thinking is embodied in language, the most common forms 
 of thought may be learned by an examination of thought expressed 
 in language. Take the following example : Light is opposed to dark- 
 ness ; feathers are light ; therefore, feathers are opposed to darkness. 
 
12 PRACTICAL LOGIC. 
 
 This is in the form of a syllogism. A syllogism embodies an argu- 
 ment, or process of reasoning. In it two propositions are compared 
 and a conclusion reached which is expressed in a third proposition. 
 This is thought as reasoning. 
 
 These three propositions are verbal expressions of judgments, in 
 which the mind compares and connects two terms. This is thought 
 as judgment. 
 
 Each of the terms in these propositions is a thought, and must be 
 understood, as is shown by the example given, if any correct think- 
 ing is to be done. This is thought as conception. 
 
 When a series of terms, propositions, arguments, etc., is grouped 
 together to make a larger whole of thought, the result is thought as 
 system. 
 
 (2.) Or looking at the subject from the thought side, instead of 
 from the language side, the same result is reached. 
 
 The comparative faculty acts in three ways : a. By comparing the 
 objects or knowledges, given by the simple cognitive faculty and re- 
 tained by the conservative faculty, and connecting them by resembling 
 attributes or marks, thus forming notions or concepts, classes and 
 general terms. This is thought as conception, b. By comparing 
 concepts or general terms and connecting them by agreement or dis- 
 agreement, resulting in judgments and propositions. This is thought 
 as judgment, c. By comparing judgments or propositions and connect- 
 ing them by the principle of reason and consequent, resulting in argu- 
 ments including syllogisms. This is thought as reasoning. 
 
 The constructive faculty also acts in three ways : a. Grouping by 
 the Law of the True, or in the form of scientific construction, result- 
 ing in scientific systems, b. Grouping by the Law of the Beautiful, 
 or in the form of artistic or aesthetic construction, resulting in artistic, 
 or aesthetic, systems, including all art productions, c. Grouping by 
 the Law of the Good, or in the form of practical construction, result- 
 ing in practical systems, including inventions, plans of conduct, etc. 
 
 It will at once be seen that the second of these forms of construc- 
 tion falls within the sphere of ^Esthetics, leaving only the first and 
 third in the sphere of Logic. 
 
 The distinct Forms of Thought with which Logic deals 
 are, therefore, as follows : 
 
 Conception, embodied in the general term ; 
 Judgment, embodied in the proposition ; 
 
THE NATURE OF LOGIC. 
 
 13 
 
 Reasoning, embodied in the argument ; 
 Construction, embodied in system, scientific and prac- 
 tical. 
 
 The facts concerning the workings of the Human Soul may be tabu- 
 lated so as to present their relations to the eye. 
 
 THE HUMAN SOUL, 
 or Man, the Conscious 
 Subject, 
 
 Knows, and, therefore, has a Cog- 
 nitive Power, or Intellect ; 
 
 Feels, and, therefore, has an Emo- 
 tive Power, or Sensibility ; 
 
 Wills, and, therefore, has a power 
 of Endeavor, or Conative Pow- 
 er, or Will. 
 
 t-3 
 
 § 
 
 © ct- 
 
 a> P 
 
 * 
 
 Man, by the COGNI- 
 TIVE POWER, 
 
 Acquires knowledges by the Simple 
 Cognitive Faculty ; 
 
 Keeps knowledges by the Conserv- 
 ative Faculty, or Memory ; 
 
 Compares knowledges, or works out 
 their Relations by the Comparative 
 Faculty ; 
 
 Constructs knowledges into Systems 
 by the Constructive Faculty. 
 
 H 
 
 o 
 
 ts 4 
 
 MAN, by the 
 DISCURSIVE 
 
 Faculties, 
 
 Compares, by 
 the Compara- 
 tive Faculty, 
 
 Constructs, by 
 the Construct- 
 ive Faculty, 
 
 Simple knowledges, in Con- 
 ception ; 
 Conceptions, in Judgment ; 
 Judgments, in Reasoning. 
 
 The True, in Scientific Sys- 
 tem; 
 
 The Beautiful, in .Esthetic 
 System ; 
 
 The Good, in Practical Sys- 
 tem. 
 
 H3 
 fc3* 
 
 o 
 
 S3 
 S3* 
 
 Topic Second. — The Practical Aim of Logic is to train to 
 Correct Thinking or Thought. 
 
 Logic, as here treated, is a practical science, aiming to 
 lead the thinker to a systematic knowledge of the laws of 
 2 
 
14 PRACTICAL LOGIC. 
 
 thought, in order to find in these the rules by which to 
 train to skill in right thinking. 
 
 1. What is Practical Science or Art ? 
 
 A science is a complete and systematic presentation of the facts and 
 principles in any sphere of knowledge, in accordance with truth. 
 Hamilton draws from Aristotle the distinction between Philosophy 
 11 Theoretical " and " Practical." " Theoretical, called likewise specu- 
 lative and contemplative, philosophy has for its highest end mere 
 truth or knowledge. Practical philosophy, on the other hand, has 
 truth or knowledge only as its proximate end, — this end being subor- 
 dinate to the ulterior end of some practical action." Notwithstanding 
 Hamilton's objections to the expressions, they are in common use, and 
 will doubtless continue in use. "Science" and "Art" are also often 
 used to express substantially the same distinction. 
 
 The sciences and arts are both systematic forms of human knowl- 
 edge. The aim of a science is to give systematic knowledge of some- 
 thing ; that of an art, to give skill in doing something. The one calls 
 for the study of scientific principles ; the other for the intelligent appli- 
 cation to practice of rules based upon these principles. A science pre- 
 sents truths to be grasped ; an art, exercises to be performed. 
 
 Practical Science, or Art, as it is sometimes called, is a 
 form of science in which the systematic knowledge of the 
 subject treated is subordinate to the training to skill in 
 some activity. 
 
 2. How far is Logic Theoretical and how far Practical? 
 
 Logic is a theoretical science, or science proper, so far 
 as it aims to give a systematic view of the laws of thought ; 
 it is a practical science, or art, so far as it subordinates 
 this to its aim to train to skill in applying the laws of 
 thought in avoiding error and arriving at truth. From the 
 scientific side, Logic should present in systematic shape the 
 laws which govern the various forms of thought, or the laws 
 by which the mind must be governed when it thinks cor- 
 rectly, i. e.j when it conceives, judges, reasons, systematizes 
 correctly. From the practical side, Logic should turn these 
 
THE NATURE OF LOGIC. 15 
 
 laws into rules and train the mind to think correctly and 
 efficiently, by training it to use these rules of thought intel- 
 ligently and skilfully. It should, if it is to be of the most 
 service, train the thinker at once to accuracy of thought in 
 reaching truth and avoiding error, and to power in using 
 the thought-faculties, — in other words, it should train both 
 to skill and power. In accordance with this view, Pro- 
 fessor Bain remarks, that although " Logic, no doubt, has a 
 certain theoretic aspect, . . . its chief aim must ever be 
 practical. Had the subject not been wanted as an aid to 
 the search of truth, it would never have been called into 
 existence/' 
 
 3. Logic aims at Correct Thinking, or at Truth. 
 
 Logic is denned, in the "Port Eoyal Logic," as "the 
 science of the operations of the understanding in the pur- 
 suit of truth." Logic aims at correct thinking 1 . Such 
 thinking is, from one point of view, thinking that is done 
 in accordance with the laws of thought which are treated 
 in works on Logic. From another point of view it is think- 
 ing which, by conformity to the laws of thought, arrives at 
 truth. 
 
 (1.) Truth. — In order to understand the meaning of these statements 
 concerning truth, there is need of considering : the nature and crite- 
 rion of truth ; the modes of arriving at truth ; the degrees of assur- 
 ance in the grasp of truth. 
 
 a. The Nature and Criterion of Truth. 
 
 According to Hamilton, truth is " the correspondence or agreement 
 of a cognition with its object." Or, including both'thought and state- 
 ment, truth is the agreement of a thought or statement with the reality 
 which the thought or statement concerns. Error is the opposite, or 
 the want of harmony between a thought or statement and its object. 
 
 The criterion, or test of truth, arises out of its nature as thus stated. 
 Does it correspond with the reality? "Man is mortal," "The sun 
 shines." " Madagascar is inhabited." " The earth is spherical." In 
 deciding whether these statements are true, the question to be asked 
 of each is, Does it agree with fact or reality f 
 
16 PRACTICAL LOGIC 
 
 b. Modes of Arriving at Truth. 
 
 The truth in any given case is arrived at in one or other of two 
 ways : 
 
 First, by the use of one's own powers intuitive or discursive. These 
 give knowledge in the narrower sense. The intuitive powers furnish 
 immediate knowledge, or a priori knowledge : (a.) By external or sense 
 perception, of matter and its phenomena; (b.) By internal perception 
 or self-consciousness, of spirit and its operations ; (c.) By intuition 
 proper, of the self-evident and necessary notions and principles which 
 underlie and condition all human experience. The discursive powers 
 furnish mediate or a posteriori knowledge by the processes of thought, 
 conception, judgment, reasoning, and construction. 
 
 Secondly, by acceptance of the statements of others. These give 
 belief in the narrow and strict sense, or the acceptance of truth on the 
 ground of testimony. Most of man's knowledge in the wide s # ense, 
 and that the most valuable part of it, is derived from this source. 
 The witnesses gain their knowledge either : (a.) By the use of their 
 intuitive powers, which lays the foundation for testimony proper; or, 
 (6.) By the use of their discursive or thought powers, which lays the 
 foundation for authority. 
 
 c. Degrees in the Assurance of Truth. 
 
 The mind does not lay hold of all its knowledge with the same de- 
 gree of certainty. . Distinction is made between belief, opinion, proba- 
 ble truth, certain truth. 
 
 Certainty is the consciousness of the necessity of agreement between 
 a thought and its object, in whichever of the above ways that thought 
 may be reached. It absolutely excludes the admission of any opposite 
 supposition. Where this is not the case, doubt and uncertainty arise. 
 
 Considered with reference to the degree of certainty, there appear, 
 at the two extremes : 
 
 Knowledge, in the strictest sense, where the consciousness of neces- 
 sity is absolute, or certainty perfect ; 
 
 Opinion, or the admission of something where the evidence is not 
 such as to necessitate a perfect certainty. 
 
 Probability appears in the approximation of the imperfect certainty 
 of opinion to the perfect certainty of knowledge. 
 
 Belief is used in various loose senses, but the distinction given above 
 will, it is thought, commend itself as the fundamental sense. Belief 
 is the acceptance of truth on the ground of testimony, including testi- 
 mony proper and authority. 
 
THE NATURE OF LOGIC. 17 
 
 (2.) Truth by Thought. — The aim of Logic is to arrive at truth 
 through the powers of thinking or thought. The grasp of the truth 
 reached will evidently depend upon the kind of truth and the accu- 
 racy of the thinking. Correct thinking will give a more or less cer- 
 tain grasp of the truth reached as the result of it. In mathematical 
 and intuitive truth the result reached is absolutely certain. In other 
 regions of thought the results of thought are more or less probable. 
 These varying degrees of certainty may be illustrated by examples. 
 It is certain that two and two cannot but make four ; that things 
 which are equal to the same thing are equal to each other ; that every 
 event must have a cause. It is probable that the first dav of January, 
 1900, will be cold. It is extremely probable that the sun will rise 
 to-morrow. It is probable that a young man of good capacity, char- 
 acter, and habits will succeed in business. It is the opinion of certain 
 astronomers that the moon is uninhabited. It is the belief of most 
 intelligent men that the earth is about 93,000,000 miles from the sun. 
 
 Topic Third. — The Principles or Laws of Thinking or 
 Thought. 
 
 Logic deals with the principles or laws which govern 
 thought. 
 
 Every rational human activity proceeds according to definite laws, 
 known or unknown. The highest degree of intelligence and efficiency 
 in any such activity requires that the laws be known and correctly 
 made use of in directing the activity. This is true of the various 
 forms of thought ; they have their laws which govern their action. 
 There are laws of conception, laws of judgment, laws of reasoning, 
 laws of construction. Logic should enable the thinker to ascertain 
 and apply these laws, and thus aid him in correct thinking and save 
 him from incorrect thinking. It is likewise true that the highest 
 degree of intelligence and efficiency in thinking requires a thorough 
 knowledge of the laws of thought and a correct use of them in guid- 
 ing the exercise of thought. Practical Logic should aim to give the 
 thinker the most thorough knowledge of the laws and the greatest 
 efficiency in using them in thinking. 
 
 Besides the special laws which govern the various forms 
 
 of thought, there are certain general laws, certain axioms 
 
 or fundamental laws and certain postulates with which 
 
 Logic sets out. The special laws will be unfolded in con- 
 
 2* B 
 
18 PRACTICAL LOGIC. 
 
 nection with the treatment of the various forms of thought ; 
 at the outset must be presented the fundamental laws and 
 postulates. 
 
 1. The Fundamental Laws of Thought. 
 
 Logic, like other sciences, has certain fundamental prin- 
 ciples upon which the more special laws rest. These are 
 usually reduced to four : 
 
 The Law of Identity, or Affirmation ; 
 
 The Law of Contradiction, or Negation ; 
 
 The Law of Excluded Middle, or Exclusion ; 
 
 The Law of Eeason and Consequent, or Sufficient Eeason. 
 
 (1.) The Law of Identity, or Affirmation. 
 
 The Law of Identity may be stated as follows : Every- 
 thing is identical with itself, or is what it is, and we may 
 affirm this of it. This has been formulated : A is A ; or 
 A = A. Whatever is, is. 
 
 The identity may be : a. Absolute, or that of total sameness of a 
 thing or thought with all its parts ; or, b. Relative, or that of partial 
 sameness of a thing or thought with each or some of its parts. The 
 logical concept or notion expressed by the general term, man, is made 
 up of the following elements : being, material, organized, animated, 
 rational, terrestrial. Man is, therefore, totally identical with all these 
 elements ; so that it may be correctly affirmed that man is material, 
 organized, animated, rational, terrestrial being. Man is partially iden- 
 tical with any of these elements ; so that it may be correctly affirmed 
 that man is material ; man is organized, etc. 
 
 The Law of Identity gives the logical right to affirm such 
 total or partial identity in all cases where it exists. It is 
 at the basis of all consistent affirmative thinking, — of all 
 positive conceptions, logical definitions, affirmative judg- 
 ments, and categorical arguments. 
 
 (2.) The Law of Contradiction, Negation, or, as Ham- 
 ilton terms it, Non-contradiction, may be stated as fol- 
 
THE NATURE OF LOGIC. 19 
 
 lows : Everything is not what it is not, and we may affirm 
 this of it. Or, conflicting attributes cannot co-exist in and 
 may not be affirmed of the same object. This has been 
 formulated : A is n't not -A. Nothing can both be and 
 not be. 
 
 The logical concepts expressed in the following pairs of general 
 terms are contradictories : black and not-black ; round and not-round ; 
 good and wicked; finite and infinite. We are logically excluded from 
 affirming the co-existence of these mutually contradictory thoughts or 
 things. A thing cannot be black and not-black at the same time and 
 in the same sense. A door cannot be open and shut (not-open) at the 
 same time and in the same sense. Black-white, round-square, good- 
 wickedness, finite-infinitude, combine mutual contradictories, and are, 
 therefore, logically excluded from correct thought by this law. 
 
 The law of non-contradiction is the complement of that 
 of identity. Its importance arises from the fact that it 
 is at the basis of all logical negation and distinction in 
 thought, — of all negative conceptions and judgments. 
 
 (3.) The Law of Excluded Middle, or Exclusion, may be 
 
 stated as follows : Of two contradictories one must be true 
 and the other false. If one is affirmed, the other is thereby 
 denied. One excludes the other, and hence there can be 
 no medium affirmation between the two. This axiom has 
 been formulated : A either is or is not. A either is or is 
 not B. Everything must either be or not be. 
 
 E. g., An intra-mercurial planet, Vulcan, exists or does not. The 
 moon either is inhabited or it is not. Bacon either was Shakespeare 
 or he was not. The two propositions, Vulcan exists, Vulcan does not 
 exist, are first tested by the Laws of Identity and Contradiction. If 
 by the Law of Identity it is true that Vulcan exists, then, by the 
 Law of Exclusion, the proposition, Vulcan does not exist, must be 
 false. If by the Law of Contradiction it be true that Vulcan does 
 not exist, then, by the Law of Exclusion, the proposition, Vulcan 
 exists, must be false. 
 
 The importance of the Principle of Exclusion arises from 
 
20 PRACTICAL LOGIC 
 
 its being the foundation of all disjunctive judgments, i.e., 
 11 of judgments in which a plurality of judgments are con- 
 tained, and which stand to each other in such a reciprocal 
 relation that the affirmation of one is the denial of the 
 other." 
 
 (4.) The Law of Reason and Consequent, or Sufficient 
 Reason. — The Law is stated as follows : All continuous 
 thought must be rationally connected. The Law has been 
 formulated : Infer nothing without a ground or reason. The 
 starting-point in continuous thinking is the affirmation of 
 some knowledge by which the mind is necessitated to affirm 
 or posit something else. This starting-point is called the 
 logical reason, ground, or antecedent, or, as Hamilton sug- 
 gests, condition; that something else which the mind is 
 necessitated to affirm or posit is called the logical conse- 
 quent, or the conditioned; the relation between the reason 
 and consequent is called the logical connection or consequence. 
 
 Reason and consequent involve not only cause and effect, but every 
 case where an antecedent compels the mind to affirm something else 
 as logically following it. It includes the relations of whole to part, 
 cause to effect, substance to attribute, etc., with the reversed relations 
 of part to whole, effect to cause, attribute to substance, etc. 
 
 The axiom, as presented by Hamilton, takes a positive and a nega- 
 tive form. 
 
 (a.) Positive Form. — "When a reason is explicitly or implicitly 
 given, then there must exist a consequent ; and, vice versa, when a 
 consequent is given, there must also exist a reason." The presence of 
 a tree as a whole always implies the presence of any or all of its parts, 
 — roots, trunk, branches. The presence of any attribute, as intelli- 
 gence, always implies the presence of the substance of which it is an 
 attribute, — mind. 
 
 (b.) Negative Form. — Where there is no reason, there can be no 
 consequent (either implicitly or explicitly). Where there is no con- 
 sequent, there can be no reason. The absence of mind involves the ' 
 absence of memory as an attribute of mind. The absence of will 
 implies the absence of moral accountability, of which it is an attribute. 
 
THE NATURE OF LOGIC. 21 
 
 The logical significance and value of the Law of Reason 
 and Consequent lies in this, " that, in virtue of it, thought 
 is constituted into a series of acts all indissolubly con- 
 nected ; 'each necessarily inferring the other." Without it, 
 continuous and connected thought or reasoning would be 
 impossible. 
 
 2. The Postulates of Logic. 
 
 There are certain fundamental postulates, or practical 
 propositions, assumed at the outset of the treatment of 
 Logic. The two here emphasized respect the reality of 
 truth, and the requirement of full, explicit statement. 
 
 (1.) The First Postulate. — There is such a thing as truth, 
 which can be ascertained, and on which all minds, acting 
 in accordance with the laws of thought, must agree. 
 
 Without this assumption there can be no starting-point 
 for thought, and no goal for the activity of the thought- 
 power. No two minds could otherwise have any common 
 basis from which to start together or on which to come to- % 
 gether in thinking or discussion. 
 
 (2.) The Second Postulate. — This, as stated by Hamilton, 
 is, " to be allowed to state explicitly in language all that is 
 implicitly contained in thought." Logic deals ultimately 
 with thought, and it has to do with language only as ex- 
 pressing thought. It is, therefore, proper to ask, in connec- 
 tion with any term, proposition, or argument, " What is the 
 thought in this?" or, in other words, "What is the full 
 and exact meaning of this?" and to state in full this 
 meaning. Abridged forms are to be completed, rhetorical 
 forms to be translated into plain language, and expressions 
 changed, if need be (provided the thought be preserved), 
 until the thought is brought out naked and entire. Mill 
 states this postulate as follows : " Logic postulates to be 
 allowed to assert the same meaning in any words which will 
 
22 PRACTICAL LOGIC. 
 
 express it ; we require the liberty of exchanging a propo- 
 sition for any other that is equipollent (that is, having equal 
 power and reach) with it." 
 
 II. THE DIVISIONS OF LOGIC. 
 
 What are the Divisions under which Logic should be 
 presented ? This question has been variously answered. 
 The answer should, in any case, depend upon the point of 
 view and object of the work. 
 
 The most common division is, perhaps, into Pure Logic 
 and Applied Logic. Hamilton divides it into Pure and 
 Modified. Eegarded as a Practical Science, it is, perhaps, 
 better to base its divisions on the various Forms of Thought. 
 
 1. Distinction of Pure and Applied Logic. — The logical 
 writers who follow the common division find it necessary to 
 define and distinguish Pure and Applied Logic, or Theo- 
 retical and Practical Logic. As these terms will constantly 
 be met with in the works on Logic, a brief explanation of 
 them will here be given. 
 
 (1.) Pure Logic is the Science of the Necessary and 
 Formal Laws of Thought as Thought. It treats of the 
 necessary laws of thought, in the strict sense of discursive 
 thought, as they are in themselves, whatever may be the 
 object-matter to which they are applied. In this sense 
 Logic is a science of abstractions, like pure mathematics or 
 metaphysics. As furnishing the principles implied in and 
 underlying the construction of all other Sciences, it has also 
 been called " the science of sciences." 
 
 (2.) Applied Logic treats of the application of the prin- 
 ciples, or laws of thought, unfolded in Pure Logic, to the 
 investigation of truth. It assists in ascertaining and foi- 
 
THE DIVISIONS OF LOGIC. 
 
 23 
 
 lowing right processes of thought and in avoiding wrong 
 processes. 
 
 This division is the same as the distinction of the School- 
 men, of Logica Docens and Logica Utens ; of the Wolfian 
 School in Germany into Theoretical and Practical ; also, as 
 General and Special, Abstract and Concrete. 
 
 The following Outline presents the common Divisions of 
 Logic from this point of view : 
 
 
 I. Theoretical, or 
 
 
 
 LOGIC, the Science 
 
 Pure, Logic, or 
 the Science of 
 these Laws in 
 themselves, in- 
 
 1. 
 
 ► 2. 
 3. 
 
 Laws of Conception. 
 Laws of Judgment. 
 Laws of Eeasoning. 
 
 of the Laws of Dis- . 
 
 cluding — 
 
 
 
 cursive Thought, 
 comprises — 
 
 
 ' 1. 
 
 The Doctrine of Fal- 
 lacies, or the modes 
 
 
 II. Practical, or 
 Applied, Logic, ■ 
 
 
 of avoiding incor- 
 rect thinking. 
 
 
 including — 
 
 2. 
 
 Method, or the right 
 modes of ascertain- 
 ing truth. 
 
 2. Distinction of Pure and Modified Logic. — Sir William 
 Hamilton divides Logic into Pure and Modified: confining 
 attention to Abstract or General Logic. 
 
 (L) Pure Logic, in the Hamiltonian sense, u considers 
 Thought Proper simply and in itself, and apart from the 
 various circumstances by which it may be affected in its 
 actual application. But human thought, it is evident, is 
 not exerted except by men and individual men.' 1 It is, 
 therefore, variously modified by individual peculiarities, 
 original and acquired, and by the circumstances of the 
 thinker. Hence arises — 
 
 (2.) Modified Logic, which considers " the conditions to 
 which thought is subject, arising from the empirical circuni- 
 
24 PRACTICAL LOGIC. 
 
 stances, external and internal, under which exclusively it 
 is the will of our Creator that man should manifest his fac- 
 ulty of thinking." 
 
 For Hamilton's Divisions, see Hamilton's " Logic," page 
 49. 
 
 3. Divisions based on the Forms of Thought. — In treat- 
 ing Logic as a Practical Science, it is more convenient and 
 satisfactory, if not more logical, to base the divisions on the 
 various Forms of Thought, — Conception, Judgment, Eea- 
 soning, and System. It is more convenient and satisfac- 
 tory, since by this method, first, the learning of the princi- 
 ples will go hand in hand with their use ; secondly, the 
 scientific view will be kept in strict subordination to the 
 practical end aimed at. It is more logical, since in this 
 way it is believed that, first, the subjects of Fallacies and 
 of Method will fall into their natural places, in connection 
 with the presentation of the laws of correct thinking ; 
 secondly, the whole subject will take such shape as is best 
 to train to skill and power in right thinking and in testing 
 the products of thought. 
 
 According to this view, Logic will be treated under four 
 Divisions : 
 
 Part First. Logic of Conception, or of the Term. 
 Part Second. Logic of Judgment, or of the Proposition. 
 Part Third. Logic of Reasoning, or of the Syllogism. 
 Part Fourth. Logic of Construction, or of the System. 
 
Part I. 
 
 THE LOGIC OF CONCEPTION OR THE TERM. 
 
 The aim of the Logic of Conception is to train the mind 
 to skill in dealing with the first and fundamental Form of 
 Thought. 
 
 Definition. — Conception is that form of thought in which 
 we compare various acquired knowledges and connect them 
 by resembling marks or attributes, thus forming Concepts, 
 Classes, and General Terms. 
 
 This definition suggests, as a first subject for treatment, 
 the formation of conceptions. The every-day practical 
 necessity for studying and logically testing the work of 
 thinkers, as embodied in their scientific, philosophic, and 
 literary productions, suggests, as a second subject, the un- 
 folding of conceptions. The Logic of Conception will, 
 therefore, be treated in two Chapters. 
 
 CHAPTER I. 
 
 THE FORMATION OF CONCEPTIONS. 
 
 Works on Logic are usually mainly confined to the work 
 of unfolding thought ; but as the process of forming con- 
 ceptions furnishes the key to their unfolding, it will be first 
 .3 25 
 
26 PRACTICAL LOGIC. 
 
 considered. The definition of conception suggests the four 
 elements of the process, to be treated in as many Sections : 
 
 First, the gathering of the materials for conception, i.e., 
 the knowledges or objects of thought. This is the work of 
 Observation. 
 
 Second, the placing of these materials side by side, 
 noting the resembling parts, marks, or attributes, and 
 gathering these into thoughts, called concepts. This is 
 Conception proper. 
 
 Third, the gathering of the objects, to which these con- 
 cepts or bundles of common attributes apply, into classes. 
 This is Classification. 
 
 Fourth, the embodying of both concepts and classes in 
 names, or general terms. This is Denomination. 
 
 The skilful thinker will need to have command of the laws of these 
 four elements of Conception : Observation, Conception proper, Classi- 
 fication, and Denomination. The last three will be seen in their 
 formation to involve comparison as an essential element. In the 
 treatment of the three in the First Chapter, both the process and 
 product will be considered. The unfolding of the products of the 
 three — the concept proper, the class, and the term — by Partition, 
 Division, and Definition, will be the work of the Second Chapter. 
 
 Section I. — Observation. 
 
 Strictly speaking, Observation is a condition rather than 
 an element of conception. It must always precede the 
 proper work of conception, since, without careful examina- 
 tion of the objects or facts about which the work of think- 
 ing is done, no material would be furnished in fit shape for 
 the use of thought in its first form. 
 
 Definition. — Observation is the mental process by which 
 we gain a minute and comprehensive knowledge of objects 
 and their make-up. 
 
 The Instruments of Observation are the Senses and Conscionsness. 
 In gaining a knowledge of the external or material world, the ob- 
 
TEE FORMATION OF CONCEPTIONS. 27 
 
 server must make use of his five senses. This is observation in the 
 narrow sense. In gaining a knowledge of the facts of the inner 
 world, or world of mind, he must make use of consciousness, or inter- 
 nal perception. This is sometimes known as reflection, or introspec- 
 tion, and, with observation by the senses, makes up observation in 
 the wide sense. 
 
 Topic First. The Predicables, or Things Knowable or 
 Nameable. — The first thing in order to observe well for the 
 purpose of correct thinking is to know the kinds of things 
 that may be known, or what the observer may expect to 
 find. This will furnish him with the clew needed to make 
 his observation exact and complete in gathering his material 
 for thinking. 
 
 From another point of view, the kinds of tilings know- 
 able or nameable are called the categories (from a Greek 
 word meaning to predicate), or the predicates (from the 
 Latin, meaning to assert), or the predicables, since they 
 sum up what may be predicated or asserted of anything. 
 
 It should manifestly be the aim of every intelligent man to acquire 
 the power to know as much as possible of what may be known and 
 named. 
 
 1. The Predicables. — Starting with being, or thing, as 
 
 the conception including all things in the universe, a simple 
 classification may be made which will be of practical value 
 to the observer. Being always appears as substance having 
 properties or attributes. Properties may be divided into 
 four kinds, reducible to three : 
 
 1st. Properties of quality, or those which constitute any- 
 thing what it is. 
 
 2d. Properties of action, or those which manifest the 
 active and passive powers of any being. 
 
 3d. Properties of condition, or those which express the 
 connections of beings with space and time. 
 
 4th. Properties of relation, or those which express the 
 connections of beings with other beings. 
 
28 PRACTICAL LOGIC. 
 
 The properties or attributes of condition and relation 
 are sometimes known together as properties of relation in the 
 wide sense, and the scheme thus reduced to three kinds of 
 properties. 
 
 Substance and property and the kindred terms need to 
 be carefully distinguished. 
 
 1. Substance is used in two kindred meanings: first, as being, in 
 contrast to and independent of its properties, as that which exists 
 absolutely and of itself, absolute being; second, "as conjoined with 
 the attributes " and furnishing their basis, that which stands under 
 and supports the attributes, the thing back of all phenomena " which 
 is and abides." In the latter and more common meaning, substance is 
 divided into matter and spirit, or that which is extended and that 
 which thinks. Subject is used in the more recent philosophy, es- 
 pecially German, to denote the spirit, " the basis of the various mental 
 phenomena." Conscious subject means the thinker or the mind itself. 
 Object is a term for that about which the knowing subject is conver- 
 sant. Subjective is applied to that which belongs to or proceeds from 
 the conscious subject; objective, to that which belongs to or proceeds 
 from the object known. 
 
 2. Various properties — called, also, attributes, qualities, parts, marks, 
 characteristics, phenomena, etc. — are the materials to be gathered, in 
 connection with substance, for conception. These terms are often used 
 in a loose sense as synonymes. The first three — property, attribute, 
 quality — are the most important, from the point of view of logic, and 
 need to be carefully distinguished; the others sufficiently explain 
 themselves. Property may be regarded as the widest of the three 
 terms, and as including whatever belongs to or pertains to any object 
 of knowledge. Quality, etymologically, is that which makes anything 
 what it is, and may, therefore, be properly regarded as including the 
 essential properties, called, in the Scheme given, properties of quality. 
 With Aristotle and Descartes, attributes are real properties, essential 
 and inherent. They may be restricted to properties of quality, or 
 extended so as to include properties of action. 
 
 Properties may be distinguished as intrinsic and extrinsic. The 
 intrinsic properties of any object of knowledge are those which are 
 inherent in the object itself. In the Categories the properties of quality 
 and action may be regarded as intrinsic. Intrinsic properties may 
 be looked upon as including what are sometimes called peculiar prop- 
 
THE FORMATION OF CONCEPTIONS. 29 
 
 erties and inseparable accidents. The extrinsic properties of any 
 object are those which arise from its connection with something exter- 
 nal rather than from its own nature. They include the properties of 
 condition and relation. 
 
 Properties are also distinguished as essential and non-essential. An 
 essential property is one of those which make any object, class, or 
 species what it is, as, in man, the faculties of sense and intelligence ; 
 in body, the dimensions of length, breadth, and thickness. An essen- 
 tial property might appropriately be called a quality, in the strict 
 etymological sense. The essential properties of any object, or those 
 which make it what it is, are known as its essence or (in the old Logic) 
 its definition. Non-essential properties are those which do not belong 
 to the essence of an object. Essential properties are substantially the 
 same as intrinsic, and non-essential as extrinsic. The former may be 
 looked upon as embracing properties of quality and of action ; the 
 latter, properties of condition and relation. 
 
 Note.— Logicians have, from the earliest times, made use of the distinctions 
 of peculiar property (often called simply property) and of accidental property, 
 or accident. A peculiar property has been defined to be one which is common 
 to the whole of a class of objects, but is not necessary to mark off that class 
 from other classes. " Capable of speaking correctly " is said to be a peculiar 
 property of man, not embraced in the definition or essence of man, "rational 
 animal." " It is, however," as Thomson has shown, " a part of the essence, 
 for rational implies it. In like manner, all the properties seem to be implicitly 
 contained in every perfect definition. No criterion can be given for distin- 
 guishing between the essence and the inseparable accompaniment of the 
 essence ; and a larger acquaintance with the nature of things makes it evident 
 that, what one science regards as a property, another must consider as essen- 
 tial, and that there is no one paramount quality which is absolutely essential 
 and can never be degraded to the rank of a property." 
 
 An accidental property, or accident, is one which may indifferently belong 
 or not belong to the objects of any class without affecting their essence. The 
 birthplace of a man and the clothes he wears are accidents which have no 
 necessary effect upon his manhood. Accidents are separable or inseparable. 
 A separable accident is one that can be changed, as the clothes of a man, his 
 position, and many other circumstances. An inseparable accident is one that 
 can never be changed, although it may have no necessary connection with 
 essential properties, as the birthplace of a man, his height, etc. Thomson has, 
 however, shown that it is often difficult, if not impossible, to distinguish acci- 
 dent from essential property. Writing in England, he says : " It is an accident 
 to the people of this country that they were born in it ; because we might con- 
 ceive them to have been born elsewhere ; but then it has modified their nature 
 or essence, and we understand by Englishman not merely one who was born 
 within the four seas, but a man of particular feelings, views, and privileges, ' 
 which are parts of his very nature. Here accident and genus or property seem 
 to become confused." 
 3* 
 
BEING, 
 
 Properties, or 
 
 Modes of 
 Substance, 
 
 80 PRACTICAL LOGIC. 
 
 It is, therefore, proposed to abandon these distinctions as at least unneces- 
 sary for logical purposes. 
 
 The Scheme of Predicables, therefore, becomes : 
 Substance, 
 
 Quality, | Intrinsic and Essential# 
 
 Action, J 
 
 Condition, -\ 
 
 V Extrinsic and Non-essential. 
 
 Relation, J 
 
 The old Aristotelian logicians looked upon all existing things as 
 being divided by nature into ten classes or categories. These, accord- 
 ing to Aristotle, are: substance, quantity, quality, relation, place, 
 time, posture, possession, action, passion. A thing that can be known 
 or named comes under one or other of these categories. As will be 
 seen at a later stage in the study of Logic, the categories will not 
 stand the test of the laws of accurate division. 
 
 It will readily be seen that these categories of Aristotle may all be 
 placed under one or other of the categories of the simpler scheme pre- 
 viously given. 
 
 2. "Use of the Predicables. — The accurate and intelligent 
 observer must consciously or unconsciously make use of 
 some such scheme in order to make his observations intelli- 
 gent and complete ; otherwise he will never know when he 
 has learned the most important facts in any given case, nor 
 when he has learned all the main facts. 
 
 The scheme will decide the general questions to be asked 
 when attention is called to any object of knowledge. 
 
 1st. What is it in its substance— spiritual or material ? This will bring out 
 what is included under Aristotle's category of substance. 
 
 2d. What are its properties of quality? This will embrace Aristotle's cate- 
 gory of quality. 
 
 3d. What are its properties of action? This will embrace Aristotle's catego- 
 ries of action and passion. 
 
 4th. What are its properties of condition ? This will take in Aristotle's cate- 
 gories of time, place, quantity, and posture. 
 
 5th. W T hat are its properties of relation? This will include Aristotle's cate- 
 gories of relation and ; 
 
 Topic Second. Observation of Things Predicable. — The 
 
 practical work of observation lies at the foundation of cor- 
 
THE FORMATION OF CONCEPTIONS. 31 
 
 rect thinking, since such thinking must depend upon first 
 ascertaining the exact facts about which it is to be done. 
 The tendency is to careless and superficial observation. Per- 
 haps more errors in science arise from want of proper obser- 
 vation of facts than from any other source. Hence the neces- 
 sity of securing, in the earlier stages of training, the careful 
 study and diligent practice of the processes and rules of 
 exact observation. 
 
 I. Processes and Products of Observation in General. 
 
 Whately styles the operation of the mind, in contem- 
 plating any object, simple apprehension. It is often called 
 intuition, or immediate knowledge. The result of this 
 operation may be called the simple notion. This notion 
 may take various forms, from that of the vaguest percept 
 to that of the complete, concrete thing. 
 
 In beginning the work of observation we apprehend ob- 
 jects, whether material or mental, with various properties 
 or parts. We perceive a tree with its trunk, branches, and 
 leaves, with their forms, colors, qualities, etc. We thus 
 gain what is called a percept of the tree. We may subse- 
 quently give special attention to any particular part or 
 property of the tree, as its height, or color, or firmness of 
 texture. This is called abstraction, or the drawing away 
 of a part or property from the concrete whole. The result 
 is an abstract, or abstract notion, of these parts or attri- 
 butes, of height, color, etc. The most important element in 
 accurate observation is mental analysis, in w T hich the atten- 
 tion is voluntarily turned to particular parts or properties 
 of any object of knowledge. This process of mental sepa- 
 ration is continued until many constituent parts of the 
 object are brought out. In examining material objects, 
 these parts may evidently be regarded either as spacial 
 parts or as attribute parts. The first point of view leads 
 to what is called physical partition, the second to mental 
 analysis proper. 
 
32 PRACTICAL LOGIC. 
 
 Physical partition is the simplest form of mental analysis. The 
 analysis of tree into roots, trunk, branches, leaves, brings out the 
 spacial parts. Such partition is of special service in the earlier stages 
 of mental training. 
 
 Praxis. — Name in an orderly manner the parts of the following 
 objects: 1. A peach. 2. A piano. 3. A ship. 4. A book. 5. A house. 
 6. A landscape. 7. A mountain view. 8. A telephone. 9. A telescope. 
 10. A locomotive. 
 
 Mental analysis proper, the more important form of observation, 
 deals with attributes rather than with spacial parts. It belongs to a 
 more advanced stage of mental training. Water may thus be ana- 
 lyzed in thought into the separate properties named weight, liquid- 
 ity, transparency, refracting power, solvent power. A dime may be 
 analyzed into the attributes or parts, material substance, heavy, 
 round, small, white, coin. 
 
 Note.— It will be obvious that chemical analysis, involving intricate proc- 
 esses of thought, belongs to a different range of mental activity. It would 
 bring out of water its chemical components, oxygen and hydrogen, and out 
 of a gold dollar its chemical components, gold and .the alloy of silver and 
 copper. 
 
 The result of the careful application of these processes 
 of abstraction and mental analysis is the notion of the com- 
 plete concrete object, or thing, which, according to Horn 
 Tooke, is the same as think, a thing being what one thing- 
 eth or thinketh. 
 
 Praxis. — Analyze and describe in an orderly way the following 
 objects : 1. A diamond. 2. A gold dollar. 3. A painting. 4. A piece 
 of wood. 5. A flower. 6. A rose. 7. A forest. 8. A sunset at sea. 
 9. A church service. 10. An act of memory. 
 
 II. Exact or Scientific Observation and its Rules. 
 
 The general and superficial observation thus far consid- 
 ered, however well it may serve the purposes of common 
 life, is insufficient for the purposes of accurate thinking. 
 Scientific observation must be made accurate and exact by 
 intelligent conformity to certain rules, and must be made 
 complete by careful use of the scheme of things knowable. 
 
 1. The Rules of Observation, which need to be grasped 
 and practised in order to reach the best results, are three. 
 
THE FORMATION OF CONCEPTIONS. 33 
 
 They are substantially Hamilton's Laws of Integrity, Par- 
 cimony, and Harmony. 
 
 Rule 1st. Observe all the essential facts, parts, or proper- 
 ties in any given case. 
 
 Rule 2d. Admit no fact, part, or property that does not 
 belong to the case in hand. 
 
 Rule 3d. Avoid all delusive mixtures of inference with 
 the facts of observation. 
 
 Rule 1st is needed to guard against the common fault of incomplete 
 observation. Through the careless use of the powers, or the holding 
 of some false theory, or the blinding influence of prejudice, men are 
 liable not to see all the facts. The honest observer should see to it 
 that none of these things stand in the way of completeness or integ- 
 rity of observation. Rule 2d is intended to guard against the danger 
 of receiving as facts things that are not such, and of receiving as facts 
 of the region under observation things which belong to some other 
 sphere of facts. This danger arises in the same way as the preceding. 
 Rule 3d is to guard against the introduction of unsound or irrelevant 
 inferences among the facts of observation. The sources of this danger 
 are the same as the preceding. Here is the fruitful source of much of 
 the scientific and philosophic error in all ages. 
 
 2. Scientific Observation, in order to the best results, 
 while conforming to these rules, must make intelligent use 
 of the categories. The observer must make use of the 
 questions, already given in connection with the scheme, in 
 order to bring out the facts of all kinds. 
 
 The character of this observation will appear more fully in the later 
 stages of the study of Logic. The mode of using the scheme may 
 here be cursorily illustrated, and the main things in the process sug- 
 gested, by the observation of a white-oak tree in the school-yard or 
 campus. Question first will bring out the fact of material substance 
 or constitution. Question second will give the facts of extension, of 
 organization, of life, and of unity of structure and plan in the tree, 
 the facts of cupnle-bearing and half-covered fruit, and the other facts 
 peculiar to the white-oak. Question third will furnish the facts of 
 growth, of resisting violence, of counteracting pressure, etc. Question 
 fourth will lead to the facts concerning the height, size, shape, habitat, 
 
 C 
 
34 PRACTICAL LOGIC. 
 
 etc., of the tree, and those concerning its time of planting, length of 
 life, periods of growth, etc. Question fifth will direct to the facts con- 
 cerning the position of the tree with reference to the school-building, 
 to other trees and objects on the grounds, to other trees belonging to 
 the class, oak, to the industrial arts in which its wood is used, etc. 
 
 Praxis. — Observe systematically and describe carefully the following 
 objects: 1. An inkstand upon the writing-desk. 2. A clock upon the 
 mantel-piece. 3. A student's lamp upon the table. 4. A Worcester's 
 Dictionary in the library-case. 5. A stove in the room. 6. A ship at 
 sea. 7. Jupiter as the evening star. 8. The centre-table in the library. 
 9. The feeling of home-sickness in the student. 10. The contemplation 
 of Church's Niagara. 
 
 Note. — The teacher will do well to use as an adjunct some such work as the 
 little Manual, published by Eldredge & Brother, entitled " The Cultivation of 
 the Senses." This will prepare the way for the application of the right princi- 
 ples to the more difficult work of introspection and analysis of mental objects. 
 
 Section II.— Conception Proper, 
 
 Conception proper is the first essential element in the 
 first Form of Thought. The work of Observation makes 
 ready the material for it; Conception proper begins the 
 work of comparing that material, arriving at the thought- 
 connections, and gathering up and combining the results in 
 a thought. 
 
 v Topic First.— The Process of Concept-Forming, 
 
 Definition, — Conception proper is the mental process of 
 fixing upon resembling parts, marks, or properties of objects, 
 and grasping them singly or together as attribute thoughts 
 or concepts. 
 
 This element of conception always involves a comparison of two or 
 more objects of knowledge, and has more or less direct reference to 
 the process of classification by similar properties. The concept may, 
 indeed, be said to be formed for the purpose of being nsed to classify 
 objects, and this gives it its chief value. There is need, therefore, of 
 considering two things : first, the gathering of similars by comparison ; 
 second, the grasping of similars in thought by conception. 
 
THE FORMATION OF CONCEPTIONS. 35 
 
 I. The Gathering of Similars by Comparison. 
 
 Comparison in the formation of concepts proper begins 
 with the work of fixing upon similar properties. Observ- 
 ing objects side by side, we note and affirm differences and 
 resemblances, and then fix upon and abstract the resem- 
 blances or properties common to the objects. 
 
 1. The simplest connecting act in thought is in finding 
 a single point of resemblance, and withdrawing, or abstract- 
 ing, this from the points of difference. 
 
 E. g., water has materiality, weight, liquidity, refracting power, 
 solvent power, transparency, etc. A dime has materiality, weight, 
 whiteness, hardness, malleability, roundness, smallness, the stamp of 
 a coin, etc. Air has materiality, fluidity, elasticity, invisibility, etc. 
 Examining these three objects side by side, they are all found to have 
 in common materiality. They resemble each other in this point, or, in 
 other words, this is a characteristic common to them all. 
 
 2. A more important connecting act in this first stage of 
 thought is that of finding and seizing upon several or all 
 the points of similarity in the objects compared. 
 
 It will readily be seen that the same objects may be ob- 
 served from different points of view. A gold or silver coin 
 may be observed as a substance having essential attributes 
 of its own, or as a piece of money used in the work of com- 
 mercial exchange. The observer should first fix upon his 
 point of view, and then seek the resemblances from that 
 point of view. 
 
 Considered as a substance, a sovereign is material, of yellow color, 
 extremely malleable, of circular shape, nineteen times heavier than 
 water, etc. As a piece of money it is of the metal gold, of compara- 
 tively high value, being worth five dollars, of the kind which is the 
 standard of values in most countries, a coin, etc. Considered as a 
 substance, a silver dollar is material, of white color, moderately mal- 
 leable, of circular shape, ten times heavier than water, etc. As a 
 piece of money it is a coin, fashioned of the metal silver, of moderately 
 high value, being worth one hundred cents, etc. Treating the gold 
 and silver coins as substances merely, they resemble each other in 
 
36 PRACTICAL LOGIC. 
 
 being material, having color, being malleable, having circular shape, 
 being of high specific gravity, etc. These are the resembling or 
 common properties or parts. Treating them as pieces of money, they 
 resemble each other in being coins, composed of metal shaped into 
 circular form and valuable for the purposes of exchange. 
 
 3. The most important connecting act in this stage of 
 thought is that of finding and fixing upon the essential 
 points of similarity in the objects compared. Scientific 
 thinking 1 , as will be seen further on, must fix mainly upon 
 the essential points of resemblance, rather than upon the 
 non-essential. 
 
 Praxis. — State, concerning the properties of the following objects, 
 whether they are intrinsic or extrinsic; whether essential or non- 
 essential; whether properties of quality, action, condition, or relation : 
 1. Of George Washington, — born in Virginia in 1732, studied mathe- 
 matics under a private instructor, tall, wise, just, brave, president, led 
 the armies of his country, the friend of Hamilton, the father of his 
 country, died in 1799. 2. Of Great Britain, — populous, fertile, insu- 
 lar, powerful, manufacturing, agricultural, commercial, philanthropic, 
 missionary, kingdom, colonizing, literary, modern, small, nation. 
 
 Compare the following objects, fixing upon some resembling prop- 
 erty, and stating to what class of properties it belongs : 1. Snow, light, 
 chalk, lime. 2. Book, parchment roll, Kosetta stone, paper manu- 
 script. 3. Oak-tree, rose, elephant, man. 4. Memory, argument, fence, 
 watch, world. 
 
 Compare the following objects, fixing upon the resembling proper- 
 ties, and stating to what class they belong : 1. Wood, coke, charcoal, 
 bituminous coal. 2. Plumbago, charcoal, diamond. 3. Star, student's 
 lamp, sun. 4. Tree, carriage, watch, poem. 5. Poem, painting, statue, 
 anthem, temple. 6. Triangle, polygon, dodecahedron, globe. 
 
 Note.— The teacher may, with great profit to the student, devote much time 
 to the processes of Observation and Comparison. They lie at the very basis of 
 correct thinking, so that their importance cannot well be over-estimated. 
 
 II. The Grasping of Similars by Conception. 
 
 The work of observation and comparison up to the pres- 
 ent point has only brought out common attributes without 
 fixing them in a thought binding them together into logical 
 
THE FORMATION OF CONCEPTIONS. 37 
 
 'unity. The attributes of the sovereign as money are named 
 each by itself. The work of conception brings together 
 all these attributes into one thought, which, as being the 
 product of conception, is called a concept, or attribute- 
 thought. This concept, which is named sovereign (in accord- 
 ance with the laws of naming to be considered under Section 
 Fourth) embraces in itself the characteristics — coin, fash- 
 ioned of the metal gold, of comparatively high value, being 
 worth five dollars, of the kind which is the standard of 
 values in most countries, etc. 
 
 The value of the product of thought reached by the 
 process of grasping together properties will depend upon 
 the method and principles followed. 
 
 1. It is obvious that any of the kinds of properties 
 already considered may be fixed upon and embodied in the 
 concept or attribute-thought, and that this may be done in 
 various ways. 
 
 a. A single property of any kind may be fixed upon, in which case 
 the result may be looked upon as a simple concept, although the 
 mental act is one of simple grasping, and not of grasping together. 
 
 b. The properties of any particular object may be grasped together, 
 without special attention to other objects, or to the principle of simi- 
 larity. This may also be regarded as an unapplied concept, which 
 may be applied later to similar objects in the work of classification. 
 
 c. The similar properties of various objects may be grasped together, 
 keeping in view the principle of similarity. This is the concept in the 
 strictest sense. 
 
 2. The Rules which must govern concept-forming, if the 
 best results are to be reached, may be reduced to two. 
 
 Rule 1st. — In order to the best thought, essential prop- 
 erties should be grasped in preference to others. 
 
 The loose thinking of common life is characterized by its seizing 
 upon non-essential properties. In observing an individual man the 
 separable accident of wearing broadcloth may be observed, abstracted, 
 and embodied in the concept broadcloth- wearing. Such a concept 
 brings out nothing essential to man. Scientific thinking, on the other 
 4 
 
38 PRACTICAL LOGIC. 
 
 hand, fixes chiefly upon essential properties, so that it embodies the 
 very nature of the objects of thought. In observing a man, it fixes 
 upon the animal and rational properties which make him what he is, 
 and embodies these in the concept man, or humanity. The products 
 of scientific thinking will be found of the utmost value in the work 
 of classifying objects. 
 
 Rule 2d. — In order to the best, the only adequate, thought 
 in this form, all the essential properties should, so far as 
 possible, be grasped. 
 
 It is obvious that any number of abstractions may be drawn from 
 any object. Strictly speaking, we can never be certain that all the 
 possible properties have been abstracted. There may always remain 
 innumerable unobserved or undetected properties. But ordinarily all 
 the essential properties may be more or less clearly detected and 
 grasped, and the perfection of the concept as a group of properties 
 will depend upon the completeness with which it takes in the essence 
 of the object of thought. 
 
 Observing carefully an animal, the properties of organized being, of 
 life, of sentiency, and of voluntary motion, are fixed upon as essential 
 properties. These are all embodied in the concept, animal. If but 
 one of these sets of properties should be embodied, the concept would 
 be of comparatively little value. Observing some virtuous act, as the 
 Prophet Daniel's act of praying to the true God notwithstanding the 
 prohibitory decree of the king, the characteristics, conformity to the 
 law of right, and intelligent, intentional action, are fixed upon and 
 embodied in the concept virtue, or virtuousness. If any one of these 
 essential characteristics is omitted in our conception of virtue, the 
 thought will be incomplete and of little value scientifically. 
 
 Praxis. — Gather up into concepts the similar properties of the fol- 
 lowing groups of objects, stating the kind of property in each case: 
 1. A piece of crayon, a chair, a lamp, a book, a tree, a stone. 2. A 
 man, an eagle, a lion, a serpent. 3. A horse, a tiger, an elephant, a 
 lap-dog. 4. A cat, a leopard, a hyena. 5. A vulture, a hawk, a 
 falcon. 6. Love, patience, joy, gratitude. 7. Faith, hope, charity. 
 
 8. Cathedral of Milan, Madonna of Raphael, Paradise Lost of Milton. 
 
 9. Great Britain, United States, Germany. 
 
 Topic Second. — The Product of Concept-Forming, 
 
 The product of gathering up the abstracted properties of 
 
THE FORMATION OF CONCEPTIONS. 39 
 
 objects in thought is a thought property or group of proper- 
 ties. It would be appropriately named a notion (from notce, 
 marks, characteristics), if that word were not used in such 
 loose and varied senses. Concept proper is, perhaps, the best 
 name. But whether spoken of as notion, concept proper, or 
 attribute thought, the essential thing in it is always the 
 grasping in thought of certain observed properties of objects. 
 
 The properties contained in any concept make up its con- 
 tent. The same thing has also been denoted by internal 
 quantity, intension, comprehension, depth, marks, etc. The 
 content of the concept man is made up of animal and 
 rational properties. The content of triangle is plane figure, 
 three-sided, rectilineal. 
 
 In connection with concepts proper, Logic gives promi- 
 nence to their reciprocal relations by content. These rela- 
 tions may be considered from two points of view : first, that 
 of identity, and, second, that of congruity. 
 
 1. Compared by content, concepts proper are distin- 
 guished as identical and different. They are — 
 
 1st. Identical, when they coincide in their marks, or comprise the 
 same properties. Identity is either absolute or relative. Absolute 
 identity, or sameness, does not strictly exist between concepts, but rela- 
 tive identity, or similarity, does exist. The terms of a complete defi- 
 nition approach most nearly to absolute identity, both comprising the 
 same marks or properties, e.g., " Body is extended substance." 
 
 2d. Different, when they do not comprise the same properties. Dif- 
 ference is again either absolute or relative. 
 
 2. Compared by content, concepts proper are also divided 
 by logicians into congruent and conflictive. 
 
 1st. Congruent notions are such as may be connected in thought 
 with the same object, as good, wise, powerful, etc. 
 
 2d. Conflictive notions are such as may not be connected in thought. 
 Conflictive opposition is either contradictory or contrary. Immediate 
 or contradictory opposites are " directly, immediately, and absolutely 
 repugnant' 1 to each other, as exemplified in yellow, not-yellow ; walk- 
 ing, not-walking. Of these conflictives there can be two only, and 
 one of them must be true. In contrary opposition, on the other hand, 
 
40 
 
 PRACTICAL LOGIC. 
 
 more than two conflictive characters are possible, as yellow, blue, red, 
 etc.; sitting, standing, lying, etc. If one of these be not predicated of 
 any person, it does not follow that any one other must be. Thus, 
 though I cannot at once sit and stand, yet I may be neither sitting 
 nor standing, — I may lie • but I must either sit or not sit ; I must 
 either stand or not stand, etc. 
 
 These relations of concepts by content may be represented to the 
 eye by diagram. Squares may be used to represent the sphere or con- 
 tent of concepts and also the objects of which they may or may not 
 be predicated. The overlapping parts of the double squares and the 
 dotted lines indicate the partial coincidence of "the properties. The 
 sign plus (-{-) may indicate congruence, the sign minus ( — ) confliction. 
 
 o 
 
 n 
 
 o 
 >> 
 
 
 tf 
 
 o 
 O 
 
 I. Identity, 
 
 Absolute, or 
 Sameness, 
 
 Relative, or 
 Similarity, 
 
 Humanity and 
 
 Rational 
 
 Animality. 
 
 Affection 
 and 
 Desire. 
 Common Element = Emotion. 
 
 H. 
 
 and 
 
 R. A. 
 
 A; ;D 
 
 2. Difference, 
 
 s. 
 
 M. 
 
 ' 1. Congruence, 
 
 Absolute, Spirituality 
 and 
 Materiality. 
 
 Touching in Being. 
 
 Relative, Science 
 and 
 Art. 
 Common Element = System of Truth 
 
 M 
 
 Good, \ 
 Wise, >in 
 Just, i 
 
 G.+ 
 
 W.+ 
 
 2. Conflic- 
 tion, 
 
 Contradictory 
 Opposition, 
 
 Contrary Op- 
 position, 
 
 LiTiD S | with P 
 acd f Paul. 
 Not-living. ) L — 
 
 :N-1.+ 
 
 Red, 
 
 Blue, 
 Green, 
 
 and 
 
 Sky. 
 
 S 
 R — 
 
 G — 
 
 B.+ 
 
THE FORMATION OF CONCEPTIONS. 41 
 
 Praxis. — State and illustrate by diagram the relation by content 
 of the following concepts: 1. Running, lying. 2. Blue, not-blue. 
 3. White, black. 4. Money, memory. 5. Learning, virtue. 6. Saint, 
 sinner. 7. Grace, unmerited favor. 8. Yellow, blue, red. 9. Walk- 
 ing, standing, sitting, running. 10. Wealth, poverty. 11. Beauty, 
 virtue. 12. Old, middle-aged, young. 13. Tall, short. 
 
 Give five examples of each of the following relations of concepts by 
 content: 1. Identity absolute. 2. Identity relative. 3. Difference 
 absolute. 4. Difference relative. 5. Congruence. 6. Contradictory 
 opposition. 7. Contrary opposition. 
 
 Section III.— Classification. 
 
 The second essential element of conception, in the wide 
 sense, may be defined as grasping in one thought, called a 
 class, all the objects to which the attributes included in 
 any concept or notion are common. Hence the process is 
 called classification. From another point of view it may 
 be defined as extending the application of the content of a 
 concept or notion to all the objects to which it is applicable. 
 Hence the process is also called generalization. 
 
 A dime has the property of roundness. When we extend the appli- 
 cation of this property to all bodies that possess it, and so connect 
 them all with dime into one thought, the result is the class, round 
 bodies. A dime has the property of whiteness. When we extend the 
 application of this property in the same manner as before, the result 
 is the class, white bodies. Making use of both round and white, the 
 result is the class, round, white bodies. Classifying by the mark, 
 stamped as coin, the result is the class of coins. 
 
 It is thus evident that the work of classification is simply the gen- 
 eral application of one or more properties of a concept to objects. The 
 resemblance of properties or attributes furnishes the key to the work. 
 If bodies had no differences, there would be but one great, monotonous 
 mass of existing things ; if they had no resemblances, no two could be 
 brought together into a group, and there would be no possibility of 
 thought. Classification is possible because objects have both different 
 and resembling properties. 
 
 Topic First. — Process of Classification. 
 
 . Classes may either be considered singly, or in systems 
 4* 
 
42 PRACTICAL LOGIC. 
 
 or combinations. Hence the ordinary distinctions and 
 rules. 
 
 1. In forming single classes, it is obvious that the thinker 
 may make use of accidental, peculiar, or essentiaj proper- 
 ties. In order to reach the most valuable scientific results, 
 classification should keep in view the most important 
 properties. 
 
 Rule. — Classify by essential properties rather than by 
 non-essential. 
 
 Gold might be classified, by the property of color, with yellow 
 objects ; silver in the same way with white objects. Such a classifica- 
 tion would, however, be of no scientific value. Taking the resembling 
 essential properties of the two: (1), they are elements or simple sub- 
 stances; (2), they possess metallic lustre; (3), they are good con- 
 ductors of heat and electricity, — they may be classified with other 
 objects having like properties, as metals. Such classification is of sci- 
 entific value. 
 
 Praxis. — Classify each of the following with like objects by various 
 non-essential and essential properties : 1. Porter's " Human Intellect." 
 2. A comet. 3. The north star. 4. The Temple of Solomon. 5. The 
 Parthenon. 6. The Washington Monument. 7. The Mississippi River. 
 8. The Mer de Glace. 9. Mount Vesuvius. 10. Victoria of England. 
 11. Ulysses S. Grant. 12. Jefferson Davis. 13. Moses. 14. Jesus. 
 
 2. Objects of knowledge are so related that they may be 
 arranged in systems of classes. Such classification requires 
 the application to classes of the process used in forming 
 single classes, while keeping in view the wider relations of 
 things. It is a successive classification of classes. 
 
 Rule. — Classify the lower classes under higher by fixing 
 upon properties common to the lower. 
 
 Certain figures are classified, by the number and relation of their 
 straight sides, as triangles, squares, parallelograms, polygons, etc. All 
 these classes have the common characteristic, being bounded by straight 
 lines, and may, therefore, be classed as rectilinear figures. Certain other 
 figures are classified, by the various character of their curved boun- 
 dary-lines, as circles, ellipses, parabolas, hyperbolas, etc. All these 
 
THE FORMATION OF CONCEPTIONS. 
 
 43 
 
 classes have the common characteristic, being bounded by curved lines, 
 and may, therefore, be classed as curvilinear figures. Rectilinear and 
 curvilinear figures have, as a common characteristic, plane surface, 
 and may, therefore, be classed as plane figures. Certain other figures 
 are classed, by the character of their bounding surfaces, as tetrahe- 
 drons, cubes," parallelopipeds, etc. They are in common bounded by 
 plane surfaces, and may, therefore, be classed as plane solids. Certain 
 other figures are classed, by the character of their bounding surfaces, 
 as spheres, cones, paraboloids, etc. They are in common bounded by 
 curved surfaces, and may, therefore, be classed as curved solids. Both 
 plane and curved solids have in common, solidity, and may, therefore, 
 be classed as solid figures. Plane figures and solid figures have in 
 common, extension, which is the subject-matter of Geometry, and may, 
 therefore, all be classed as geometrical figures. The result is a System 
 of Classes: 
 
 O 
 
 3 
 be 
 
 
 Triangles, 
 
 
 
 
 Squares, 
 
 Rectilinear 
 
 
 Polygons, 
 
 Figures. 
 
 
 etc. 
 
 
 
 Circles, 
 
 
 - Plane Figures. " 
 
 Ellipses, 
 
 Parabolas, 
 
 Hyperbolas, 
 
 Curvilinear 
 Figures. 
 
 
 etc. 
 
 
 Tetrahedrons, 
 
 Cubes, 
 
 Parallelopipeds, 
 
 Plane 
 ' Solids. 
 
 
 etc. 
 
 Spheres, 
 Cones, 
 
 Curved 
 
 • Solid Figures. J 
 
 Paraboloids, 
 
 - Solids. 
 
 
 etc. 
 
 
 
 
 Geometrical 
 Figures. 
 
 Such systems are found on the most extensive scale in the classifi- 
 cation of animals and plants, in Zoology and Botany. Exercises in 
 forming systems of classes may be drawn from these sciences. 
 
 Praxis. — Classify the following collections or masses of objects in 
 single classes and in systems of classes: 1. The articles in a school- 
 room. 2. The objects in a school or college campus. 3. The struc- 
 
44 PRACTICAL LOGIC 
 
 tures in New York city. 4. The objects comprised in a farm. 5. The 
 objects embraced in a Pennsylvania landscape. 6. The objects in the 
 heavens as revealed by a powerful telescope. 7. The operations of the 
 human soul. 8. The things seen. 9. The things unseen. 
 
 Topic Second. — Results of Classification. 
 
 The product of the general application of the concept to 
 all the objects to which it is common is a thought-group, or 
 a thought-system, of objects, i.e., a class or a system of 
 
 In the general notion as class, the essential thing is 
 always the grasping together of individuals. The indi- 
 viduals contained in any such general notion make up its 
 extent. The extent has also been denoted by external quart- 
 tity, extension, breadth, etc. 
 
 In connection with the class notion and extent, Logic 
 gives prominence to two things : first, the relations of gen- 
 eral notions as classes to one another by extent ; second, the 
 reciprocal relations of extent and content, or of the class 
 and the concept proper. 
 
 I. Relations of Classes to One Another. 
 
 1. Compared by extent, general notions as classes stand 
 to each other in five mutual relations: exclusion, co-exten- 
 sion, subordination, co-ordination, and intersection. 
 
 1st. Exclusion. — One class excludes another when no part of the 
 one coincides with any part of the other; e.g., horse and syllogism. 
 No horse is ever a syllogism, and vice versa. 
 
 2d. Co-extension. — One class is co-extensive with another when each 
 includes exactly the same species ; e. g., living being and organized 
 being. Using life as including plant life, every living being is an 
 organized being, and vice versa. 
 
 3d. Subordination. — One class is subordinate to another (which is 
 called the super ordinate) when the former is included in the latter as a 
 part of it; e.g., dog, horse, under quadruped. Every dog is a quad- 
 ruped, as is also every horse. 
 
 4th. Co-ordination. — Two or more classes are co-ordinate when they 
 are co-exclusive, yet all immediately comprehended under the same 
 
THE FORMATION OF CONCEPTIONS. 
 
 45 
 
 higher class ; e. g., dog, horse, while immediately subordinate to the 
 higher class, quadruped, are co-exclusive and, therefore, co-ordinate. 
 
 5th. Intersection. — Two classes intersect each other when each is 
 partially included in the other ; e. g., rational and animal. Some 
 rational beings are animals and some are not, and vice versa. 
 
 These relations may be symbolized by Euler's circular 
 notation, in which the extent of classes is represented by 
 circles, and the relations of classes by the relative positions 
 of the circles. 
 
 1. Exclusion. 
 
 Horse, syllogism. 
 
 J5 
 3 
 
 o >» 
 
 03 
 
 2. Co-extension. 
 
 Living being, organized being. 
 
 3. Subordination. 
 
 Quadruped, horse. 
 
 4. Co-ordination. 
 
 Quadruped, lion, horse. 
 
 5. Intersection. 
 
 Rational being, animal. 
 
 Starting from Inclusion, other logicians divide the rela- 
 tions of classes into those of (1), Inclusion, embracing, 
 (a), Co-extension, and (6), Subordination; (2), Intersec- 
 tion ; (3), Exclusion, embracing, (a), Co-ordination, and 
 (&), Non-co-ordination. 
 
 2. Special Relations arising from Classification. 
 
 Out of classes and systems of classes arise various logical 
 distinctions which, as they occur constantly in science and 
 philosophy, in the writings of the modern as well as ancient 
 masters, should be understood by the student who expects 
 to read and think for himself. 
 
46 PRACTICAL LOGIC. 
 
 (1.) The simpler forms of classification give rise to the 
 distinctions of genus, species, differentia, individual. 
 
 In any series of higher and lower classes, each higher class is a 
 genus to those next below it. Those classes next below the genus are 
 its species. Caucasian, Mongolian, Malaysian, Negro, and American 
 Indian are species of the genus, man. Or, if European is considered as 
 a genus, German, Frenchman, Englishman, etc., are the species. Dif- 
 ferentia, or specific difference, is the characteristic or property, simple 
 or complex, which distinguishes one species from others under the 
 same genus. Eed is the differentia of red rose, or that which distin- 
 guishes it from white, yellow, and other species of the genus, rose. An 
 individual is one of the single objects of which a species or genus is 
 always made up. It is only capable of physical or mechanical par- 
 tition, and can never be a genus. Washington and Napoleon are 
 individuals. 
 
 Note.— Species, in its peculiar use in Natural History, needs to be carefully 
 distinguished from species in Logic. In Natural History, species means only 
 "such a class of animals as has, or might have, descended from a single origi- 
 nal pair, and the varieties of which may permanently interprop agate among 
 themselves." The sub-species are named varieties. Greyhound, spaniel, ter- 
 rier, bull-dog, etc., are varieties of the species, dog. 
 
 (2.) Systems of classes give rise to the logical distinc- 
 tions of summ-um genus, infima species, subaltern genera 
 and species, proximate genera and species, superordinates, 
 subordinates, co-ordinates, and disparates. 
 
 The highest class in any system of classes is known as summum 
 genus ; the lowest class, which can never be a genus, as infima species. 
 The absolute highest genus is being, which includes all the existences 
 in the universe. In classifying any department of knowledge, it is 
 usual, however, to assume and start from some relative highest genus. 
 In Botany, this genus is plant; in Zoology, animal. Subaltern genera, 
 or sub-classes, are those which are species of a higher genus. Subal- 
 tern species, or sub-species, are species of some higher species consid- 
 ered as a genus to those lower than itself. White oak, black oak, 
 scarlet oak, yellow oak, etc., are subaltern species of oak. Oak is a 
 species of the genus, mastwort, or cup-bearing trees, and constitutes, 
 with chestnut, beech, hazel, and hornbeam, the subaltern genera, or 
 sub-classes, of that class. 
 
 This may be illustrated by the following tabular example : 
 
THE FORMATION OF CONCEPTIONS. 
 
 47 
 
 Designations. 
 
 Summum Genus. 
 
 Species or Subaltern Genera. 
 
 Intermediate or Sub-Species. 
 
 Infima Species. 
 
 Individuals. 
 
 Classes. 
 
 Being or Thing. 
 Organic (Inorganic). 
 Animal (Plant). 
 Man (Brute). 
 Washington (Other Men). 
 
 Genera and species, which are next to each other in order of ascent 
 or descent in any system of classes, are known as proximate genera 
 and species, or nearest classes and species ; as animal and man, in the 
 example just given. The higher genus in relation to a lower is called 
 the superordinate genus, or next in rank above ; the lower in relation 
 to the higher, the subordinate, or next in rank below. The species 
 under any genus are co-ordinates, or of equal rank. This may be 
 illustrated by the following example : 
 
 Assumed Highest Genus, — Cup-bearing Trees. 
 
 Species. 
 
 c3 
 
 Oak. 
 
 Chestnut. 
 
 Beech. 
 
 Hazel. 
 
 Hornbeam. 
 
 Red, 
 
 American, 
 
 American, 
 
 American, 
 
 Ironwood, 
 
 White, 
 
 Spanish, 
 
 Red, 
 
 Beaked, 
 
 Hornbeam, 
 
 Black, 
 
 Dwarf, 
 
 etc. 
 
 etc. 
 
 etc. 
 
 etc. 
 
 etc. 
 
 
 
 
 Oak, chestnut, etc., are superordinates with reference to the co- 
 ordinate species respectively embraced under them. The co-ordinate 
 species, red, white, etc. ; American, Spanish, etc., are subordinates to 
 oak and chestnut respectively, and these last to the higher genus, cup- 
 bearing trees, which embraces also beech, hazel, and hornbeam. Any 
 one of these co-ordinates, considered in relation to a higher or lower 
 part in the divisions of any of the other co-ordinates in the system of 
 classes, is called disparate. Red oak as compared with chestnut is 
 disparate. 
 
 II. Reciprocal Relations of Concepts and Classes. 
 
 The concept and class notions are both very closely con- 
 nected with one another, and embodied in one word. From 
 one point of view the word man means the rational and 
 animal properties which make man what he is. It has, 
 therefore, content or contained properties. From another 
 point of view man means all the individuals that have these 
 
48 PRACTICAL LOGIC. 
 
 common properties, or all mankind. It has, therefore, 
 extent or comprehended objects. The Rule expressing the 
 relation of content and extent is, that as the content in- 
 creases the extent diminishes, and as the extent increases 
 the content diminishes. 
 
 In other words, the greater the number of properties in a concept, 
 the less the number of objects that have all these properties in common, 
 and the greater the number of objects in a class, the less the number 
 of properties common to them all. This may be illustrated by the 
 following diagram of concept and class in content and extent : 
 
 Concept Content, Extent, 
 
 and i. e., the properties con- i. e., the objects embraced 
 
 Class. tained in the concept. in the class. 
 
 Body. Extended substance. Stone, Plant, Brute, Man, etc. 
 
 Living Body. Body with life. Plant, Brute, Man. 
 
 Animal. Body with life and sensation. Brute, Man. 
 
 jj an f Body with life, sensation, and ) -y- 
 
 1 reason. / 
 
 Washington. { Bod y with life > sensation, reason, j IndividuaL 
 I Father of his country. i 
 
 From this diagram it is apparent that the concept, body, which has, 
 as its content, only extended substance, has the greatest extent, em- 
 bracing stone, plant, brute, man, etc., while the lowest concept, man, 
 which has, as its content, extended substance with life, sensation, and 
 reason, has the least extent, embracing only mankind. Washington, 
 with still broader content, has, as its extent, only an individual. 
 Being, the concept of least possible content, containing simply exist- 
 ence, is the absolute highest class, and has the greatest possible extent, 
 embracing all things material and spiritual. 
 
 Praxis. — Give five illustrations of each of the following relations 
 of classes: 1. Exclusion. 2. Co-extension. 3. Subordination. 4. Co- 
 ordination. 5. Intersection. 
 
 State and illustrate, by diagram and by circular notation, the rela- 
 tions of the classes: 1. Man, horse. 2. Dog, ox, alligator. 3. Book, 
 manuscript. 4. Magazine, daily paper. 5. Planet, body moving round 
 the sun. 6. Aryan, European, Frenchman. 7. Faith, hope, love. 
 8. Affection, desire. 9. Man, animal. 10. Plant, tree. 11. House, 
 barn. 12. Botany, Geology. 13. Mathematics, Astronomy. 
 
 Illustrate by three examples each : 1. Genus, species, differentia, 
 
THE FORMATION OF CONCEPTIONS. 49 
 
 individual. 2. Highest class, lowest species, sub-class, sub-species, 
 superordinate, subordinate, co-ordinate, disparate. 3. The varying 
 relation of content and extent. 
 
 Section IV.— Denomination. 
 
 When, by the processes of conception, concepts and classes 
 have been formed, they need to be embodied in language in 
 order that they may be fixed and made subject to recall for 
 further use. This is the third essential element in Concep- 
 tion. 
 
 Topic First. — The Process of Naming. 
 
 Language is the expression of thoughts by means of 
 words spoken or written. It is the medium of communi- 
 cation between men. It fixes thoughts which would other- 
 wise be vague, or fleeting, or confined to some individual, 
 and makes them the property of all. It thus greatly facili- 
 tates the progress of our thinking. In short, while it is 
 true that some of our processes of thought may be carried 
 on without any language, it is nevertheless true that with- 
 out it thought would practically cease, while communica- 
 tion would become impossible. 
 
 I. Modes of Naming. 
 
 In giving names to our conceptions, the aim should be to 
 embody them as perfectly as possible and bring them as 
 fully as may be Under the recall and control of ourselves 
 and others. It is evident that this aim is not always kept 
 in view. Things are named in various ways, and the names, 
 judged by the mode in which they are given, are oftener 
 non-logical than logical. 
 
 1. The name is sometimes purely arbitrary. This is often the case 
 with the strictly proper name. u It denotes an individual, but does 
 not indicate or imply any attribute of that individual. . . It is an 
 unmeaning mark or sign which we connect in our minds with an 
 object, &o that when this sign meets our eyes or ears we may think of 
 5 D 
 
50 PRACTICAL LOGIC. 
 
 that individual." The most profane of men may be named Christo- 
 pher, Christ-bearer. 
 
 2. The name is sometimes given from some accidental circumstance 
 or property. In proper names this is illustrated by such Bible names 
 as Moses, drawn out; Isaac, laughter. In common or class names, the 
 same process is illustrated by moon, measurer ; planet, wanderer ; vul- 
 ture, flyer; lord, loaf -keeper. 
 
 3. The name sometimes embodies some prominent essential property 
 or mark. This is illustrated by such words as sun, shiner; man, 
 thinker ; animal, breather; barometer, weight-measurer. 
 
 4. The perfect or strictly logical name aims to embody as completely 
 as possible the entire essence of a conception. As such naming is 
 difficult in the case of complex conceptions, it is usually necessary to 
 fix upon some prominent essential property, in accordance with the 
 principle already given. The essential marks in the conception, man, 
 are rational and animal, but the Aryan people who named man seized 
 upon the essential mark, thought, and so called him man, i. e., thinker. 
 
 5. Names, as languages are constituted, are often, in fact, little more 
 than mere hints, which start the mind on its work of interpretation. 
 This has been shown by Hamilton to be one of the necessities of lan- 
 guage, — since, unless the vocabulary becomes almost infinite so as to 
 express all our single notions, the same words must be used to express 
 a multitude of thoughts, more or less differing from each other. See 
 Hamilton's Logic, p. 437. 
 
 II. Rules for Naming. 
 
 The Eules for giving names to our conceptions naturally 
 arise from the aim in naming. 
 
 Rule 1st. — Name a conception what it is. 
 
 The science of the human soul should be named, not mental philoso- 
 phy, nor intellectual philosophy, nor metaphysics, nor philosophy, but 
 psychology. 
 
 Rule 2d. — Make the name self-interpreting if possible. 
 
 A name is notative when it suggests its own marks (notes), and thus 
 becomes self-interpreting. It is symbolical when it serves as a symbol 
 or label of properties or marks which it does not suggest. Names 
 should be notative, if possible, in order to give the mind the best start 
 in its work of interpretation. It is a fact to be noted, that many 
 
THE FORMATION OF CONCEPTIONS. 51 
 
 names which were originally notative have lost their power of sug- 
 gestion except to men who are educated. To one who would best 
 understand thought as expressed in English, acquaintance with the 
 languages from which the English has drawn its words becomes a neces- 
 sity. To. one acquainted with Latin, triangle, quadruped, biped, become 
 notative and self-interpreting. To one having the mastery of Greek, 
 democracy, oligarchy, oxygen, mythology, philosophy, become self- 
 interpreting. To one understanding Anglo-Saxon, lord, wicked, battle, 
 war, orchard, become self-interpreting. To one versed in Philology 
 and History, heathen, villain, church, sincere, saunter, become self- 
 interpreting. 
 
 Rule 3d. — Make the name as simple as possible. 
 
 As the genius of our language is Saxon, let the preference be given 
 to Saxon, and, if possible, let the name be a single word. Pierce is 
 better than penetrate ; love is stronger than affection, and hate than 
 animosity ; working is more forceful than operation. Psychology, as 
 being one word, is better than intellectual philosophy; arithmetic 
 than the art of computation. 
 
 Rule 4th. — In naming a system of conceptions or classes, 
 use a system of names. 
 
 In a system of names one may be made to suggest all the other 
 names and thoughts. Such system is thus of immense advantage, 
 especially in the various Sciences. In the Natural History Sciences, 
 which deal largely with classes, a system of distinctions has been 
 adopted by which the precise place of each logical genus and species 
 in the great system of classes may be accurately fixed. In Zoology, 
 the Animal Kingdom is separated by Agassiz into Branches, Classes, 
 Orders, Families, Genera, Species, Varieties. 
 
 Praxis. — Test the following names by the rules for naming, stating 
 whether they are notative or symbolical: 1. Intellectual Philoso- 
 phy, for science of the human soul. 2. Paternal ancestor, for father. 
 3. Affection, for love. 4. Sierra Nevada Mountains. 5. Telegraph, 
 6. Geology. 7. Geography. 8. Academy. 9. School of herring. 10. Ac- 
 cident. 11. Blackboard. 12. Candlestick. 13. Ambition. 14. Navy. 
 15. Book. 16. Bible. 17. Volume. 18. Parchment. 19. Paper. 
 20. Pen. 
 
52 PRACTICAL LOGIC. 
 
 Topic Second. — Products of Naming. 
 
 The products of naming concepts and classes are the 
 various kinds of terms in which our notions are embodied. 
 The divisions are based, (1), either upon something in the 
 term itself; or (2), upon something in the relations of 
 terms. 
 
 I. Kinds of Terms arising out of the Nature of the Term 
 itself. 
 
 The term involves in itself three elements, — mark or 
 property, object, name. 
 
 1. Considered as made up of marks, terms are divided, 
 (1), by the presence or absence of such marks into positive 
 and non-positive; (2), by the separation or connection of 
 the attributes with objects, into abstract and concrete. 
 
 (1.) All terms are either positive or non-positive. A positive term 
 is one that implies the presence of some real mark or property, as 
 man, tree, good. A non-positive term is one that implies the absence 
 of such mark or property, as not-man, nncertain, deaf. Non-positive 
 terms are either negative or privative. A negative term is one that 
 implies simply the absence of any real mark, as not-tree, not-good, 
 uncertain. Terms apparently negative are often positive in reality, 
 as immortal, the word meaning not only not subject to death, but 
 living for ever. So terms apparently positive are often negative, 
 as idle, which is equivalent to not working, or not disposed to work. 
 Privative terms are equivalent to a positive and negative term taken 
 together. They mark the absence of certain properties, and the pres- 
 ence of others, from which the presence also of the former might nat- 
 urally have been expected. Such terms are, blind, unkind, unholy. 
 Blind is not equivalent to not seeing, nor to not capable of seeing, but 
 signifies deprivation of sight in some being which might have been 
 expected to have it. 
 
 (2.) All terms are either abstract or concrete. Abstract terms are 
 those which embody abstracts or marks or properties as apart from 
 the objects to which they properly belong, as coldness, hardness. Of 
 the innumerable abstracts formed, the mind suffers the greater number 
 to pass without naming, but fixes some by names. Thus in observing 
 some individual man, the abstracts, life, intelligence, feeling, self* 
 
THE FORMATION OF CONCEPTIONS, 53 
 
 activity, etc., are seized upon and fixed singly by names ; or several 
 of them together, under one name, as intelligence, feeling, etc., under 
 rationality ; or all the marks together under humanity. Concrete 
 terms present the marks or qualities in connection with the objects to 
 which they belong, or (as indicated by the derivation of the word 
 from the Latin con and cresco, or con and cerno) with which they are 
 grown together or seen together, as the adjective terms, cold, hard, and 
 the substance terms or substantives, ice, iron, man. 
 
 2. Considered as embodying objects, terms are divided, 
 (1), by the number of objects embodied, into singular and 
 universal; (2), by the connection of the objects with their 
 marks, into connotative and non-connotative. 
 
 (1.) All terms are either singular or universal. Singular terms are 
 those in which our percepts or simple apprehensions are embodied, or 
 our general notions as connected with our perceptions ; as, Shakespeare, 
 the Great Eastern, this man. They begin with embodying simple no- 
 tions, but gradually rise toward the expression of thought proper or 
 general notions. They are of three kinds : proper names, individual- 
 ized common names, and collective names. Proper names are singular 
 concrete terms which denote an individual, but do not necessarily 
 indicate or express any properties of that individual; as, George 
 Washington, Alexander Hamilton. There is, however, a tendency in 
 the progress of thought to connect with and designate by the proper 
 term the peculiar qualities of the individual denoted by it. We say 
 of a man he is a Washington or a Csesar — meaning to bring out his 
 patriotism and equanimity or his ambition and universal genius. An 
 individualized common term is one which expresses the simple notion 
 of an object as it is presented to us in the concrete with more or less 
 of its properties ; as, this table, this man, yonder mountain. It is 
 usually formed by adding some individualizing or limiting word to a 
 common or general term ; as, this table, that man, an organ, my hat. 
 The collective term is also properly a singular made up of many 
 objects brought together into the unity of a mass, rather than that of 
 a class ; as, the House of Commons, the army, a regiment, a forest. 
 
 The universal term is that in which the general notion, embracing 
 concept proper and class, is embodied. It is universal, as it embraces 
 all the objects possessing the common marks or properties involved in 
 it as an attribute term. It is common, or general, since it is applicable 
 to any and every one of these objects, as living, or man, is applicable 
 5* 
 
54 PRACTICAL LOGIC. 
 
 to every individual of the human race. It differs from the collective 
 term, which embraces a number of things joined together in one mass, 
 as regiment, Congress, since the collective is not applicable to each and 
 every object under it. Every being embraced under the general term, 
 man, is a man ; but every soldier embraced under the collective term, 
 army, is not an army. When the concept proper, or complement of 
 marks or properties in a general term, is made prominent, it is used as 
 a concept, or attribute, term; when the class, or complement of objects 
 embraced in it, is made prominent, it is considered as a class term. In 
 the propositions, Jesus was man ; Jesus was a man, — the meaning of 
 the first is, that Jesus had the marks or properties of a man ; of the 
 second, that he belonged to the class, man. In the first proposition 
 man is a concept or attribute term ; in the second, a class term. 
 
 (2.) All terms are either connotative or non-connotative. A conno- 
 tative term is one which denotes an object, and notes along with it a 
 mark or property. A non-connotative term is one which signifies an 
 object only or a property only. All proper names are non-connota- 
 tive, since they denote objects, but connote no property; as, Wash- 
 ington, London. All abstracts of qualities, as whiteness, length, are 
 non-connotative, as they denote only properties without connoting 
 any objects. All adjectives, as white, just, and all concrete general 
 names, as bird, fish, are connotative, since they denote objects and 
 connote properties. 
 
 3. Considered as words, terms are divided, (1), by self- 
 interpretation, into notative and non-notative or symbol- 
 ical; and (2), by the number of words constituting the 
 term, into simple and complex. 
 
 (1.) All terms are either notative or symbolical. This distinction 
 has already been defined and illustrated under the Second Kule of 
 Denomination. 
 
 (2.) All terms are either simple or complex. A simple term is one 
 which consists of only one word. But some words cannot be used as 
 terms, although they may form parts of terms. Hence arise complex 
 terms, which are made up of combinations of words. With reference 
 to their being used as terms, words are either categorematic (from a 
 Greek word, to assert or predicate), i. e., such that they can stand 
 alone as complete terms in propositions ; or syncategorematic (from 
 the Greek, to assert or predicate along with), i. e., such that they can 
 only form parts of terms, since they must be used with other words to 
 
THE FORMATION OF CONCEPTIONS. 55 
 
 make up complete terms. To the former belong the noun, adjective, 
 and certain parts of the verb. There are, however, those who con- 
 tend that in the last analysis only nouns can form terms. Such sen- 
 tences, as " Dictionaries are useful," must be completed by adding 
 books or things; thus, " Dictionaries ' are useful books." Adverbs, 
 prepositions, conjunctions, etc., are syncategorematic. We speak of 
 "the conservation of energy," "the conflict of religion and science," 
 thus uniting many conceptions in one, and embodying them in a 
 phrase. In the statement, "This is a faithful saying, and worthy of 
 all acceptation, that Christ Jesus came into the world to save sinners" 
 the part italicized is a term expressed in a sentence. Complex terms 
 are formed by combining syncategorematic with categorematic words. 
 Any of the objects and properties included under the Predicables may 
 thus be combined in complex terms. 
 
 II. Kinds of Terms arising out of the Relations of Terms. 
 
 Terms are divided, 1, by their relation to one another, 
 into relative and non-relative or absolute; and, 2, by their 
 relation to the objects of which they are predicated, into 
 compatible and incompatible. 
 
 1. All terms are either relative or non-relative. A relative term is 
 one which implies some other of which we may predicate it as its cor- 
 relative, as father, son ; ruler, subject; cause, effect. Non-relative or 
 absolute terms are such as do not imply any such relative object or 
 correlative, as tree, stone. 
 
 2. All terms are either compatible or incompatible. Compatible 
 terms are such as can be applied to the same object at the same time. 
 Contrary terms are the most opposed that can be conceived as appli- 
 cable to the same object at the same time, as wise and foolish, good 
 and bad. They are not compatible, however, when used in a strict 
 sense ; since anything which is absolutely good cannot be in any sense 
 bad. Incompatible terms are such as are entirely excluded from appli- 
 cation to the same object in the same sense at the same time. All 
 contradictory terms are incompatible, as wise and not-wise, black and 
 not-black. 
 
 These various distinctions of terms, embodying impor- 
 tant distinctions in thought, are to be met with more or 
 less frequently in all the profounder discussions in science, 
 philosophy, and theology. Most of them will be found to 
 
56 PRACTICAL LOGIC. 
 
 be of value in the subsequent portions of Logic. They may 
 readily be presented in outline form by the student. 
 
 Praxis. — Apply all the foregoing distinctions, as far as possible, to 
 the following words: 1. Government. 2. Industry. 3. Art. 4. Agri- 
 culture. 5. Joy. 6. Jupiter. 7. This earth. 8. The consolations of 
 philosophy. 9. Intemperance. 10. Foolish. 11. Sobriety. 12. Hope- 
 fulness. 13. Psychology. 14. Virtue. 15. Non-relative. 16, Abso- 
 lute. 17. Immortal. 18. Deaf. 19. From. 20. Life. 
 
 Select, from the page preceding the praxis, the following kinds of 
 terms or words: 1. Negative. 2. Privative. 3. Simple. 4. Complex. 
 5. Concrete. 6. Abstract. 7. Relative. 8. Absolute. 9. Singular. 
 10. Universal. 11. Syncategorematic. 12. Notative. 13. Symbolical. 
 14. Connotative. 15. Non-connotative. 16. Abstract. 17. Concrete. 
 18. Collective. 19. Attribute. 20. Class. 
 
 CHAPTER II. 
 THE UNFOLDING OF CONCEPTIONS. 
 
 Conception, in its three essential elements, conception 
 proper, classification, and denomination, has been found to 
 result in three products : 
 
 First, the Concept Proper, embracing content or contained 
 properties ; 
 
 Second, the Class, embracing extent or included" individ- 
 ual obj ects ; 
 
 Third, the Term, embodying both concept proper and 
 class, and, therefore, to be regarded either as an attribute 
 term or as a class term. 
 
 The processes of unfolding these products, or of ascertaining accu- 
 rately and exhibiting systematically and completely what is con- 
 tained in them, are the processes at the foundation of all right and full 
 understanding of the materials of which discourse, whether spoken or 
 written, is made up. It is evident at once that a man who does not 
 understand what is involved in such conceptions as cause, force, expe- 
 
THE UNFOLDING OF CONCEPTIONS. 57 
 
 rience, persistence, can neither think nor discourse intelligently con- 
 cerning them, and can neither hear nor read intelligently anything 
 that others may say or write, which involves these conceptions, 
 
 As the products of conception are three, the processes of 
 unfolding are three : 
 
 First, the unfolding of the content of the concept proper, 
 This has been named Metaphysical Analysis, but has also 
 been called Logical Partition. 
 
 Second, the unfolding of the extent of the class, This is 
 known as Logical Division. 
 
 Third, the unfolding of the term. This will be known 
 as Logical Definition. 
 
 Logical Partition, Division and Definition will, there- 
 fore, furnish the subjects of the three Sections embraced 
 under the Unfolding of Conceptions. 
 
 Section I.— Logical Partition. 
 
 Logical Partition is that form of analysis which takes a 
 concept proper, as a complex of properties or attributes, 
 and unfolds the component properties. In other words, 
 Logical Partition is the complete and orderly statement of 
 the parts of the content of a concept, or the separation of 
 a complex attribute into its component attributes. 
 
 The thought-whole analyzed in partition is the concept 
 proper which is an attribute or intensive w T hole. 
 
 The mind contemplates the objects presented to it nnder three kinds 
 of wholes : 
 
 1st. Mathematical or Quantitative Wholes, or Wholes of strict In- 
 tuition. This includes two kinds : 
 
 a. The Numerical, based on Time. 
 
 b. The Geometrical, based on Space. 
 
 2d. Essential or Physical Wholes, or Wholes of Observation. This 
 includes two kinds : 
 
 a. The Substance, as composed of substance and attributes. 
 
 b. The Causal, as composed of cause and effects. 
 
58 PRACTICAL LOGIC. 
 
 3d. Logical Wholes, or Wholes of Discursion or Thought. This 
 includes two kinds : 
 
 a. The Attribute or Intensive Whole, or Whole of Content. 
 
 b. The Class or Extensive Whole, or Whole of Extent. 
 
 A mathematical whole, called also a quantitative, an intuitive, an 
 integrate, whole, is, according to Hamilton, one composed of integral, 
 or, more properly, integrant parts. It is a whole every part of which 
 lies out of every other part, while all the parts together make up the 
 integer or complete whole. Thus in the integrate spacial whole of the 
 human body, the head, body, and limbs, its integrant parts, are not 
 contained in, but each lies -out of, each other. When the parts of an 
 integrate spacial whole are separate and accidentally thrown together, 
 the result is a mass whole, as a gallon of water, a pile of wheat, a 
 block of wood. When the parts of an integrate numerical whole are 
 thus separate and accidentally thrown together, the result is a collect- 
 ive whole, as an army, a forest. These wholes are analyzed by 
 mechanical or physical partition. 
 
 An essential whole, called also a physical whole and a whole of 
 observation, is the kind of whole with which observation brings us in 
 contact. It consists of substance and properties either of quality or 
 of action. The parts do not lie out of each other, but substance and 
 property permeate and modify each other. Thus in gold the material 
 substance is inseparably connected and blended with the properties of 
 quality and action, metallic and reflecting the yellow rays of light. 
 These wholes are analyzed by the process of mental analysis already 
 described. 
 
 A logical whole, called also a whole of thought, is the product of 
 the power of conception, and is, therefore, a creation of thought. As 
 a concept proper it is analyzed by logical partition ; as a class whole, 
 by logical division. 
 
 Logical analysis by partition and division, therefore, 
 deals with the logical whole in its two forms, partition 
 having particularly to do with the logical whole as an 
 attribute whole. The aim of partition, to unfold the con- 
 tent of an attribute whole, will, in connection with the 
 nature and make-up of this whole as already learned from 
 the formation of the concept proper, suggest the forms and 
 rules of the process. 
 
THE UNFOLDING OF CONCEPTIONS. 59 
 
 Topic First. — The Forms of Logical Partition, 
 
 The purpose of the thinker in partition is to attain to 
 completeness in the work of unfolding the marks or prop- 
 erties of the concept. Such completeness may be either 
 relative or absolute. This gives the two forms of partition. 
 
 I. Relatively Complete Partition, 
 
 A partition is relatively complete when complete from 
 the thinker's point of view or for his special purpose. It 
 is obvious that it is not always the aim to bring out 
 all the possible properties included in the four predicable 
 classes. Thus the chemist may desire to bring out the 
 properties of gold as an element or as a metal ; the banker, 
 as a medium of exchange ; the encyclopaedist, in these 
 and all other aspects. It is thus manifest that any one 
 of many points of view may be made available, the choice 
 being always governed by the object of the thinker. 
 
 The point of vievr may be some one of the four kinds of prop^. 
 and the aim to reach the component parte from this point of view. 
 The concept man may be parted by qualitative properties into ration- 
 ality and animality ; or by active properties, or as a causal agency, 
 into self-acting, thinking, feeling, etc. ; or by properties of condition, 
 into temporal, terrestrial, etc. ; or by relative properties, into depend- 
 ent, responsible, sinful, etc. 
 
 Or the point of view may be a single aspect of some one of the four 
 kinds of predicable properties. E. g. t taking active properties as the 
 starting-point, man as a causal agency operates in many d::. 
 spheres, and may, therefore, have the properties unfolded with ref- 
 erence to any one of these spheres. The thinker may be a phy 
 and so may regard man materially, as counterpoising more or less 
 weight and excluding other objects from the sam- He may be 
 
 a chemist and so may regard man chemically, as forming, by decom- 
 position, nitrogen, carbon, and other chemical elements. He may be 
 a physiologist and so may regard man organically, as breathing, 
 digesting, etc. He may be a political economist and so may regard 
 man industrially, as farming, manufacturing, trading, or as producing, 
 transporting, consuming, etc. He may be a psychologist and so may 
 
60 PRACTICAL LOGIC. 
 
 regard man spiritually, as thinking, feeling, willing, etc. He may be 
 a theologian and so may regard man religiously, as recognizing, long- 
 ing after and worshipping God, etc. 
 
 II. Absolutely Complete Partition. 
 
 A partition is absolutely complete when the aim is to 
 give an exhaustive analysis of a concept, or to present all 
 the kinds of properties. 
 
 In such partition the various characteristics of man, as given from 
 the four points of view, would all be embraced. Or, to take another 
 example, gold may be parted by qualitative properties, as material, 
 solid, elementary substance, etc. ; by active properties, as reflecting the 
 yellow rays of light, conducting heat and electricity, counterpoising 
 great weight, etc. ; by relative attributes (including condition and 
 relation proper), as being mainly confined to particular regions of the 
 earth, being of great value as a precious metal, being the standard of 
 values in exchange, etc. 
 
 Topic Second. — The Rules of Logical Partition. 
 
 The rules for logical partition are determined by its aim 
 to unfold systematically, from some definite point of view, 
 the properties or attributes contained in a given concept. 
 
 Rule 1st. — The thinker in partition should first fix upon 
 a single complement of attributes, should then determine 
 upon the proper point of view for the purpose he has in 
 mind, and should finally adhere to this point of view 
 throughout the entire partition. 
 
 This is the law of unity. The danger of violating it arises from 
 the fact that language uses the same term or the same form of ex- 
 pression for very different concepts or bundles of properties. Man, 
 from the point of view of the physiologist, has very different marks 
 from man as considered in social science or in psychology or theology. 
 Physiology considers man as a material, organized, living being; 
 social science, as a member of society and having certain social wants 
 and instincts ; psychology, as a spirit embodied ; theology, as a crea- 
 ture and subject of God. The law of unity requires that the proper 
 point of view be fixed upon and prohibits the mixing up of proper- 
 ties belonging to man from these various points of view. 
 
TEE UNFOLDING OF CONCEPTIONS. 61 
 
 Rule 2d. — A partition should be complete from its point 
 of view, or inclusive of the whole complement of proper- 
 ties divided. 
 
 This is a form of the general law of completeness or adequacy or 
 integrity. So far as a partition is incomplete it omits something essen- 
 tial to the conception, and thus fails to give that distinct view which 
 requires that all the parts be presented in their proper relation to each 
 other. Moreover, incomplete partitions are necessarily partial or one- 
 sided, and will inevitably lead to positive error. If, for example, in 
 analyzing faith as a Christian virtue, we recognize only the marks, 
 knowledge, assent or intellectual belief, and sentiment or response of 
 the heart, leaving out all moral disposition or purpose, we make faith 
 involuntary, and so take from it the essential element of all virtue. 
 Such faith ceases to be a virtue. Mr. Mill falls into a like error in 
 analyzing cause, as invariable antecedence, thereby omitting efficiency, 
 the principal and essential property involved in causation. 
 
 Prof. Day, in writing of the general Law of Adequacy in analysis, 
 says: " The practical importance of a careful observance of this Law 
 of Logical Analysis is to be seen in the fact that by far the greatest 
 part of erroneous opinion in all departments of knowledge arises from 
 the incomplete apprehension of the objects of knowledge. Most dis- 
 sensions in science and in belief would be ended by a complete survey 
 of all the constituent elements of the matter in dispute. It is mainly 
 because the parties look, one at one element, the other at another, and 
 each to the exclusion from his view of some element or character im- 
 portant to a correct opinion, that any dissension arises." This holds 
 with special force in partition, since this process deals with the prop- 
 erties, involved in the essential nature and make-up of things, upon 
 which all scientific classification depends. 
 
 If, for example, murder is analyzed into the elements, taking of 
 human life, deliberate purpose, then the act of the sheriff in hanging 
 a murderer, or the killing of another in self-defence, would be murder. 
 The essential element of malice is omitted in the analysis. Or, again, 
 if virtue is analyzed as embracing intelligence and conformity to the 
 law of right, omitting intention, then the act of every hypocritical 
 Pharisee in giving alms might be termed virtuous. On the other 
 hand, if right intention is embraced in the partition, and conformity 
 to the law of right omitted, the acts of the fanatic and enthusiast 
 might be termed virtuous. It is only by taking in all the elements 
 that error is escaped. Or, once more, if the characters of the rose are 
 6 
 
62 PRACTICAL LOGIC. 
 
 given, as a shrub, producing flowers, having thorns, the rose might be 
 confounded with any thorn-bush. All such possibilities of error are 
 eliminated when the characters are fully enumerated as they are in 
 the scientific text-books of Botany. 
 
 Rule 3d. — A partition should be exclusive, i. e. t it should 
 shut out all marks or characters not belonging to the sub- 
 ject. 
 
 This rule corresponds to the Law of Parcimony under observation. 
 It is violated if education is made to embrace, drawing out of the 
 powers, putting them to use by their proper exercise, in the study of 
 the physical sciences, in a scientific school. The use, the kind of study, 
 and the place are none of them essential to the process, and they should, 
 therefore, be excluded. So money may be analyzed into the charac- 
 ters, stamped metal, means of exchange. This, however, would not 
 apply to most of the money in use in civilized lands, as most of it is 
 not metallic. Money embraces the characters, representative of value, 
 means of exchange, passing current, so that metallic is not an essen~ 
 tial characteristic. 
 
 Rule 4th. — A partition should be orderly in the arrange- 
 ment of the component elements. 
 
 This requires that some principle of arrangement should 
 be seized upon and made use of in the statement of the 
 elements of the complex thought analyzed. It also requires 
 that in any continued process of partition the elements ob- 
 tained should be arranged so as to bring out the relations 
 of co-ordination and subordination. 
 
 In analyzing man, in its intrinsic elements, by partition, we may 
 begin with the visible and tangible and proceed to the higher invis- 
 ible and intangible. The resulting partition will be, animal attributes 
 or animality and rational attributes or rationality. Analyzing ani- 
 mality, we may again proceed from lower elements to higher. The 
 result will be, attributes of matter or corporeity, of organization, of 
 life, of sentiency, of voluntary motion. On the same principle of pro- 
 cedure, rationality will yield the properties of intelligence, emotion, 
 and endeavor. The rule given requires such orderly procedure and 
 arrangement in the work of partition. In the partition of man, it 
 
THE UNFOLDING OF CONCEPTIONS. 63 
 
 would forbid the mingling of the two sets of attributes and the co- 
 ordination of any of the set of attributes resulting from the second 
 step in the partition, as sentiency, with animality or rationality. 
 
 In an exhaustive process of partition each of these elements should 
 be still further divided into its component properties, until the ulti- 
 mate elements are reached. For example, corporeity would give 
 extension in length, breadth and thickness, weight, etc. Organization, 
 life, etc., would each be found to yield component elements co-ordinate 
 with those of corporeity. 
 
 Praxis. — Give exhaustive Partitions of the following Concepts, test- 
 ing the work by the Rules : 1. Money. 2. Englishman. 3. The love 
 of God. 4. Life. 5. Salvation. 6. Genius. 7. Despair. 8. Forgive- 
 ness. 9. Heaven. 10. Duty. 11. Manliness. 12. Wisdom. 13. Jus- 
 tice. 14. Beauty. 15. Prophet. 16. Foresight. 17. Value. 18. For- 
 titude. 19. Egotism. 20. Selfishness. 21. History. 22. Philosophy. 
 23. Benevolence. 24. Charity. 25. Eternity. 26. Omnipotence. 
 27. Politeness. 28. Explanation. 29. Confirmation. 30. Design. 
 
 Give the component elements of the following Concepts, stating the 
 kind of whole and the point of view, and showing that the Partition 
 is in each case made in conformity to the Pules given : 1. The violet. 
 2. The diamond. 3. Botany. 4. Habit. 5. Hope. 6. Affection. 
 7. Religion. 8. Art. 9. Fine Arts. 10. The orange. 11. Carbon. 
 12. Monsoon. 13. Partition. 
 
 Examine the following Partitions, stating the kind of whole and 
 the point of view, showing whether they conform to the Rules, and, 
 in case they do not, correcting or completing the Partition according 
 to the Rules : 
 
 1. Government = Intelligent power, ordered by law, controlling 
 action. 
 
 2. Duelling = Fighting of two persons, mutual agreement, intent to 
 kill, deadly weapons. 
 
 3. Lie = Enunciation of what is false, intent to deceive, violation 
 of some obligation to give to others the truth. 
 
 4. Novel = Fictitious story, central interest in love, artistic con- 
 struction. 
 
 5. Contract = Two parties, mutual promise, mutual obligation. 
 
 6. Charity = Compassion and sympathy for the needy, kindly and 
 affectionate provision for the need, wise administering of the relief. 
 
 7. Circle = A curved line, drawn round a given point. 
 
 8. Planet = A star wandering in the heavens. 
 
64 PRACTICAL LOGIC. 
 
 9. Triangle = A plane figure, three sides, three angles equal to two 
 right angles. 
 
 10. Parallelogram === A plane figure, four-sided, opposite sides equal 
 and parallel, opposite angles equal. 
 
 11. Fluid = Material substance, yielding easily to pressure, parts 
 readily changing relative position without separation, gaseous form. 
 
 12. Whale == A large fish, living in cold regions, useful, yielding oil. 
 
 13. Education = Instruction, moral discipline, training. 
 
 Section II.— Logical Division. 
 
 Logical Division is that form of logical analysis which 
 takes a conception as a genus or class whole and unfolds its 
 component species. In the words of Ueberweg : " Division 
 is the complete and orderly statement of the parts of the 
 extent of a notion, or the separation of a genus into its 
 species." 
 
 Note. — The student needs to distinguish carefully between partition and 
 division. The former takes a concept proper or attribute whole and separates 
 it into its component properties ; the latter takes a genus or class whole and 
 separates it into its component species made up of individuals. 
 
 The grounds or principles of division are found in the 
 concept proper, . or the common properties by which the 
 objects in the class were originally classified. These prop- 
 erties embodied in the concept proper, and making up its 
 content, have been called the base, since they are at the 
 foundation of both concept and class. The possible prin- 
 ciples of division in any given case are, therefore, only 
 limited by the number of properties and combinations of 
 properties, intrinsic and extrinsic, contained in the base 
 and unfolded by partition. 
 
 Thus the class man has a content or base of two complex intrinsic 
 properties, animality and rationality. The class may be divided by 
 any property embraced in these. It may be analyzed into animal 
 parts, — by the material properties, of extension in length, of weight 
 and of color, giving tall and short ; heavy and light ; white, tawny, 
 and black : by the properties of organization, giving sanguine, nerv-. 
 ous, and bilious ; etc., etc. Or man may be divided into rational 
 
THE UNFOLDING OF CONCEPTIONS. 65 
 
 parts, — by different properties of intelligence, giving cultivated and 
 uncultivated ; enlightened and barbarous ; learned and unlearned ; 
 imitative and creative ; etc,: by the comparative prominence of the 
 intelligence, sensibility, and will, giving intellectual, sentimental, and 
 practical. Or it may be divided by both animal and rational parts 
 combined, — by language, giving Aryan, Semitic, and Turanian ; by 
 race constitution, giving Caucasian, Mongolian, etc. ; and the like. 
 Man has also a base of many extrinsic properties, or properties of con- 
 dition and relation, which may also furnish innumerable other prin- 
 ciples of division. It may thus be divided by relation to place, as 
 European, Asiatic, etc. ; islanders and dwellers on the continents ; 
 men of the torrid, temperate, and frigid zones ; and the like : by rela- 
 tion to time, into ancient and modern ; or ancient, mediaeval, and 
 modern; antediluvian and postdiluvian ; old, middle-aged, and young ; 
 and the like : or by relation proper, into bond and free ; rulers and 
 ruled ; and the like. 
 
 Topic First — The Forms of Logical Division, 
 
 The principal forms of logical division are the artificial 
 or dichotomous and the natural. Either of these may be 
 single and unextended or complex and extended. 
 
 1. The simplest form of division is the artificial or di- 
 chotomous, or that which arrives at two members which are 
 contradictories. 
 
 For example: animals are rational and irrational, or vertebrate and 
 invertebrate ; angles are right and not-right or oblique ; oblique 
 angles are acute and not-acute or obtuse; the ancients were Jews 
 and Gentiles, or Greeks and barbarians, or bond and free. 
 
 Such division is said by the logicians to be strictly 
 logical, considering merely the form of the thought and 
 not requiring any knowledge of what the concepts mean 
 in order to assure us that the division is correct and ex- 
 haustive. But, as Ueberweg has remarked, "it labors 
 under the defect that the species classed under the nega- 
 tion are left indefinite. Through the unimportance of the 
 principle of division, or by reason of the number of species 
 included in the negative and contradictory notion, the 
 division may become worthless." 
 6* E 
 
66 
 
 PRACTICAL LOGIC 
 
 Thus, the division of the universe into partridges and not-partridges 
 is of no value, both because of the worth lessness of the ground of 
 division and the indefiniteness of the negative notion. 
 
 The process of dicliotoinous division may be extended 
 
 until the lowest species or individuals are reached. There 
 are two forms of this extended diehotoxnous division, a loose 
 form and a strict one. 
 
 In the loose form the principles of division are seized upon suc- 
 cessively as the new occasions of division arise. This is illustrated 
 by what is known, from its author, the Greek logician Porphyrius, as 
 
 the Tree of Porphyry, which, 
 
 Substance. 
 
 Corporeal. 
 
 Animate. 
 
 starting with substance as the 
 highest genus, closes with man 
 as the lowest species, and with 
 Socrates, Plato, etc., as the indi- 
 viduals. 
 
 It will be observed that the 
 successive principles of division 
 are the qualities implied in cor- 
 poreal, animate, sensible (or sen- 
 tient), and rational. It is evident 
 that the divisions on the nega- 
 tive side, incorporeal, insensate, 
 etc., are also capable of like sub- 
 division with those on the posi- 
 tive side. 
 
 In the stricter form of diehot- 
 omous division, one principle of 
 division is carried through the 
 entire series of subdivisions. In 
 this case it is necessary to select 
 at the outset some mark or attri- 
 bute of the original class, as the 
 principle on which the successive 
 divisions shall be made. This 
 
 may be illustrated by dividing man or mankind by religion as the 
 
 principle of division. 
 
 Sensible 
 
 Eational. 
 
 Incorporeal. 
 
 Inanimate. 
 
 Insensible. 
 
 Irrational. 
 
 Socrates, Plato, and others. 
 
THE UNFOLDING OF CONCEPTIONS. 
 
 67 
 
 
 Mankind 
 1 
 
 
 
 The 
 
 ists 
 
 Atheists 
 
 Mon otheists 
 
 Polytheists 
 
 
 Chris 
 
 tians xson- Christians 
 
 Papists 
 
 Anti-Papists 
 
 Jes 
 
 uits 
 
 
 
 
 Non-Jesuits 
 
 Loyola and others 
 
 In this example, religion, in the various forms in which it appears 
 amoDg mankind, furnishes successive principles of division* The suc- 
 cessive marks or characteristics used are. a personal God, the one God, 
 God in Christ, the control of the Pope, Jesuitical principles. 
 
 2. The most perfect form of division is natural division. 
 
 "It founds itself," as Ueberweg has said, " on the essen- 
 tial modifications of the essentially constitutive (or intrin- 
 sic) attributes. It depends on the essential parts of the 
 notion or class to be divided. It is called natural division 
 in the same sense as the system which results from a con- 
 tinuous series of such divisions is to be called a natural 
 system." 
 
 It is evident that divisions of this kind cannot he formed in any 
 way according to an external uniform scheme. It is incorrect to look 
 for an equal number of members of division in all cases in divisions 
 of this kind. Thus the animal kingdom, divided by plan of structure, 
 gives, by the four distinct kinds of structure, vertebrates, articulates, 
 molluscs, and radiates. These four divisions are again taken up and 
 subdivided in the Natural System of Zoology. Confining the natural 
 subdivision to the vertebrates, we find at least five subdivisions recog- 
 nized by zoologists, — mammals, birds, reptiles proper, amphibians, and 
 fishes. Again, human duties, divided by the object toward which they 
 are directed, naturally fall into the divisions, individual, social, and 
 theistic. The student may also turn to the classification of the cupule- 
 bearing trees, as already given, for another illustration of natural 
 division. The natural divisions are seldom dichotomous. 
 
68 PRACTICAL LOGIC. 
 
 3. From both dichotomous and natural division often arise 
 the trichotomy or threefold division, and the polytomy or 
 
 manifold division. 
 
 From the examples already presented, it is manifest that natural 
 division is often found to be trichotomous or polytomous. It is like- 
 wise true that these forms may arise from a condensed statement of 
 extended dichotomous division. Angles are divided, by the degrees 
 of difference in the direction of the sides, into acute, right, and obtuse. 
 This is a trichotomy condensed from an extended dichotomy, as fol- 
 lows : angles are right and not-right ; angles not-right are acute and 
 obtuse. The trichotomy is drawn from this. Mankind are Christians, 
 Jews, Mohammedans, polytheists, and atheists, is a polytomy con- 
 densed from an extended dichotomous process, as follows: 
 
 
 Mankind 
 1 
 
 
 
 The 
 
 ists Atheists 
 
 Mon 
 
 otheists 
 
 Polytheists 
 
 Christian 
 
 LS 
 
 
 Non-Christians 
 
 Jews and Mohammedans 
 
 The trichotomy often arises because the parts of the class divided 
 are not sharply marked off or separated from each other. Thus, men 
 divided by color are white, tawny, and black. The present condition 
 of a sentient being may be one of pleasure, of indifference, or of pain. 
 Men divided by age are young, middle-aged, and old. Action con- 
 sidered morally is good, indifferent, or bad. 
 
 Topic Second. — The Rules of Logical Division. 
 
 The rules for division naturally arise out of its nature 
 and aim. They spring either from the principle of division, 
 from the various relations of the parts or species to the 
 whole or class divided, or from the relations of the divisions 
 and subdivisions to each other. 
 
 Rule 1st. — In a logical division the first requirement is 
 to fix upon the one principle of division suited to the pur- 
 pose in view, and the next to adhere to it throughout. 
 
THE UNFOLDING OF CONCEPTIONS. 69 
 
 Several particulars need to be noted and emphasized in 
 connection with this rule. 
 
 1. There must be some principle of division in every 
 case as the reason or ground for the division. This is self- 
 evident, for, as Hamilton has said, " otherwise there would 
 be no division determined, no division carried into effect." 
 
 2. The principle of division is always to be sought in 
 some common mark or property, intrinsic or extrinsic, of 
 the class to be divided, and should be clearly and defi- 
 nitely grasped. 
 
 In general, it is manifest that the essential or intrinsic properties 
 (those of quality and action) have most to do with determining the 
 character of the class and its species. These properties must, there- 
 fore, furnish the most important principles, or those of natural division. 
 In dividing man, rationality and animality furnish more character- 
 istic divisions than the extrinsic properties (those of relation). 
 
 The particular end which the thinker has in view must, however, 
 regulate the choice of the principle of division, so that in certain cir- 
 cumstances that principle is found in extrinsic or relative properties. 
 Man is divided by intrinsic properties, mental and physical constitu- 
 tion, into Caucasian, Mongolian, etc. Geographically, man may need 
 to be divided, by the relative property, place of abode, into European, 
 Asiatic, etc. 
 
 In all cases the principle of division, whether intrinsic or extrinsic, 
 should be clearly and definitely grasped. Failure in this inevitably 
 leads to incoherent, uncertain, and unsatisfactory results. Thus when 
 sentences are divided into indicative, interrogative, imperative, and 
 exclamatory, no principle of division is apparent ; we are left uncer- 
 tain whether these are all the kinds of sentences and whether they 
 should all enter into a proper division. 
 
 3. Every division should have only one principle. 
 
 The result of not complying with this requirement is what is called 
 cross-division. This fault brings confusion and perplexity. The 
 division of governments into monarchical, republican, despotic, aristo- 
 cratic, and hereditary, violates this principle. The first, second, and 
 fourth of these divisions have as their ground, the persons by whom 
 the authority is exercised ; the third has its ground in the extent of 
 
70 PRACTICAL LOGIC 
 
 the control ; the fifth in the tenure of office. Monarchy and aristoc- 
 racy may be despotic or hereditary, or both or neither. In short, the 
 divisions cross each other in various ways and the whole is hopelessly 
 confused. The same thing is illustrated by the division of books into 
 poetry, history, Latin, French, German, morocco, and cloth. Three 
 principles of division are made use of: the subject-matter, the lan- 
 guage in which written, and the kind of binding. This results in 
 many and perplexing cross-divisions. 
 
 4. The principle of division should always be one of 
 some importance and value. 
 
 This excludes all useless and foolish divisions, but especially the 
 counterfeit of dichotomy known as division by infinitation. To divide 
 the universe of being into man and not-man ; or the animal kingdom 
 into parrots and not-parrots, may have a show of logic, but the result, 
 as already seen, is absolutely worthless. 
 
 5. The principle of division should always be suited to 
 the purpose. Very different divisions of the same class 
 may be required for different ends. 
 
 For the purposes of Philology, a division of conjunctions, by the 
 words from which they are derived, into verbal, adjective, substantive, 
 phrase or prepositional, and composite, might possibly be of some 
 service ; but as a division for the purposes of grammar (which gives 
 attention to the thought embodied rather than the origin of words) it 
 has no relevancy and is of no value. For the purposes of Grammar, 
 the principle of division should be, by the relations of the sentences or 
 parts of sentences to each other, into co-ordinate and subordinate. 
 These again should be subdivided, by the special forms of co-ordination 
 and subordination, into copulative, adversative, etc., final, conditional, 
 etc. For the purposes of Philology it would be as absurd to divide 
 man into producers, transporters, and consumers, as it would to divide 
 man, for the purposes of Political Economy, into Aryan, Semitic, and 
 Turanian. 
 
 Rule 2d. — A division should be complete or inclusive of 
 all the species of the class divided. 
 
 These species into which a class is divided are called 
 the members of the division. 
 
 If these species or members of the division taken to- 
 
THE UNFOLDING OF COXCEPTIOXS. 71 
 
 gether do not exactly equal the class, then the division is 
 evidently only partial and imperfect. This rule may be 
 transgressed in various ways, as has been shown by writers 
 on logic. 
 
 1. The rule is transgressed when members of a division are left out. 
 For example, when we divide the actions of men into good and bad. 
 To this we should add, indifferent. 
 
 2. The rule is transgressed when a subdivision is co-ordinated with 
 a division, as when we divide mathematical figures into solids and 
 plane surfaces. It should be solids or surfaces, since this is the funda- 
 mental division (by the number of dimensions), and plane and curved 
 surfaces are subdivisions of surfaces by another principle. 
 
 3. We violate the rule when we bring in a dividing member too 
 much, as when we divide mathematical figures into solids, surfaces, 
 lines, and points. Here the last two elements, lines and points, must 
 be excluded, since lines and points, though elements of mathematical 
 figures, are not themselves figures. 
 
 Rule 3d. — The members of a division should be recipro- 
 cally exclusive. 
 
 This requires that each specific part brought oat should 
 be entirely different from every other such part. 
 
 1. This rule is violated by placing a subdivision above ot beside a 
 division under which it belongs, as when human actions are divided 
 into necessary, free, and moral. Free actions are either moral or 
 indifferent. In this case, therefore, a subdivision of free actions, 
 which is included under it, is placed by the side of it. Or. again, 
 when the sphere of Natural History is divided into the animal, vege- 
 table, and mineral kingdoms, and the vertebrates ; vertebrates is sub- 
 ordinate to animal, and as a subdivision of it should be excluded from 
 enumeration with it. 
 
 2. The rule is also violated when more principles of division than 
 one are used. For example, when we divide human actions into neces- 
 sary, free, useful, and detrimental, two principles of division are used, 
 necessity and ntility, and the result is that the enumeration covers the 
 whole class of human actions twice. 
 
 Rule 4th, — A division should proceed immediately from 
 proximate genera to proximate species. 
 
72 PRACTICAL LOGIC 
 
 Divisions should, as far as possible, be continuous, that is, the notion 
 must first be divided into its proximate, and then into its remoter 
 parts, and this without overleaping any one part ; or, in other words, 
 each part must be immediately subordinated to its own whole. It is, 
 therefore, improper to divide animals into elephants, birds, fishes, etc. 
 According to Cuvier, as modified by Agassiz, the system of Zoology 
 which gives the true division of animal is as follows : 
 
 Kingdom Animal. 
 
 Branch Vertebrates, Articulates, Mollusks, and Radiates. 
 
 Class Mammals, Birds, Reptiles, Fishes, etc. 
 
 Elephants belong under mammals. In the division given, the inter- 
 mediate classes, vertebrates and mammals, are overleaped. 
 
 Such an overleaping is, however, sometimes allowed for the sake of 
 brevity; but this only when the omitted members can be readily sup- 
 plied in thought. This is illustrated by the common mathematical 
 division, already given, of triangles, into right, acute, or obtuse. 
 
 Ride 5th. — A division should be orderly in the arrange- 
 ment of the specific parts into which the class is divided, — 
 i. e. y the parts should be placed in proper co-ordination and 
 subordination. 
 
 This is simply the requirement that in the statement of a system of 
 division everything should be put in its own place. The rule may be 
 illustrated hj the Intellect or Power of Cognition, beginning with the 
 Simple Cognitive Faculty. 
 
 Cognitive Power or Intellect (divided by progressive stages of 
 knowing) : — 
 
 1. Simple Cognitive Faculty (by kind of knowledges acquired), — 
 (1.) Internal Perception or Self-Consciousness, giving knowledge 
 
 of self; 
 (2.) External Perception or Sense, giving knowledge of external 
 
 world ; 
 (3.) Intuitive Perception or Intuition Proper, giving knowledge 
 
 of first truths. 
 
 2c Conservative Faculty or Memory (by psychological elements in 
 keeping knowledges), — 
 
THE UNFOLDING OF CONCEPTIONS. 73 
 
 ' (1.) Retention, keeping knowledges, ont of consciousness ; 
 
 (2.) Reproduction or Association of Ideas, bringing back knowl- 
 edges by linking them together ; 
 
 (3.) Representation or Imagination, vividly imaging the knowl- 
 edges reproduced ; 
 
 (4.) Recognition, connecting the present image with the past 
 knowledge. 
 
 3. Comparative Faculty or Thought (by material compared), — 
 
 ' (1.) Conception or Comparison of Objects, forming concepts, 
 
 classes, and terms ; 
 (2.) Judgment or Comparison of Concepts, forming judgments 
 
 and propositions; 
 (3.) Reasoning or Comparison of Judgments, forming arguments 
 
 and conclusions. 
 
 4. Constructive or System-making Faculty (by law followed), — 
 (1.) Scientific Construction or Construction by the True, giving 
 
 scientific system; 
 (2.) Artistic Construction or Construction by the Beautiful, giving 
 
 {esthetic system ; 
 (3.) Practical Construction or Construction by the Good, giving 
 
 practical system. 
 
 It will be observed that neither of the four main divisions can 
 change place with any other. Simple cognition, or the power of 
 acquiring our simple and fundamental knowledges, must act before 
 there can be anything for memory to conserve; conservation or 
 memory must act before comparison can have any material to elab- 
 orate; comparison must do its work in order to furnish the materials 
 for construction. The powers subordinate to these four must likewise 
 take their proper places of subordination. 
 
 Praxis. — Give Divisions of the following Classes, stating clearly the 
 Principles of Division and whether Artificial or Natural, and testing 
 the work by the Rules : 1. The Races of Men. 2. The Nations of the 
 Earth. 3. Languages. 4. Fruits. 5. Heavenly Bodies. 6. Commerce. 
 7. Art. 8. Industries. 9. Governments. 10. Churches. 11. Emotions. 
 12. Desires. 13. Ships. 14. Triangles. 15. Quadrilaterals. 16. Laws. 
 17. Life. 18. Dogs. 19. Metals. 20. The Carnivora. 21. Plants. 
 22. Roses. 23. Stars. 24. Processes of Rhetorical Invention. 25. Phys- 
 ical Forces. 26. Colors. 27. Divisions of time. 28. Flowering Shrubs. 
 7 
 
74 PRACTICAL LOGIC. 
 
 29. The ruminants. 30. Insects. 31. Forms of religion. 32. Civiliza- 
 tions. 33. Laws. 34. Societies. 35. Educational institutions. 36. Me- 
 chanic arts. 37. Wars. 38. International alliances. 39. Homicides. 
 40. Social conditions. 41. Human relationships. 42. The rocks. 
 43. Occupations. 44. Systems of unbelief. 45. Monotheistic systems. 
 46. Periods of human history. 47. Theistic systems. 48. Diversities 
 of genius. 49. Poets. 50. Phases of religious character. 51. Tem- 
 peraments. 52. Influences in formation of character. 53. Influences 
 of the Crusades upon European civilization. 54. Aims in life. 55. Mo- 
 tives influencing human conduct. 56. Benefits of international com- 
 merce. 
 
 Give extended and complete Divisions, Dichotomous or Natural, of 
 the following Classes, stating the Principle and testing by the Rules : 
 1. The vegetable kingdom. 2. Furniture. 3. Birds. 4. Cereals. 
 5. Fishes. 6. Creeds of Christendom. 7. The Sciences. 8. Foods for 
 man. 9. Views of the origin of the universe. 10. Forces of civili- 
 zation. 
 
 Examine each of the following Divisions, stating the Principle of 
 Division, showing whether the Division is Natural or Artificial and 
 whether it conforms to the Rules ; and, in case it does not, showing 
 wherein it fails and correcting and completing it : 
 
 1. Triangle = equilateral and equiangular. 
 
 2. Triangle = right-angled, isosceles, and scalene. 
 
 3. Literature = history, oratory, and poetry. 
 
 4. Literature = writings historical, religious, poetical, classical, and 
 current. 
 
 5. Government = democracy, oligarchy, aristocracy, and monarchy. 
 
 6. Government = absolute, limited, constitutional, and free. 
 
 7. Government = empires, kingdoms, dukedoms, and republics. 
 
 8. The fine arts = the arts of free beauty, the arts of dependent 
 beauty, and the arts of utility. 
 
 9. The arts of free beauty = music, sculpture, painting, and poetry. 
 
 10. The arts of dependent beauty = architecture, landscape-garden- 
 ing, embroidery, and decorative painting. 
 
 11. Rectilinear figures = triangles, quadrangles, rectangles, paral- 
 lelograms, and polygons. 
 
 12. Sentence — simple, compound, and complex. 
 
 13. Proposition = categorical, hypothetical, conditional, and dis- 
 junctive. 
 
 14. Proposition = affirmative, hypothetical, and negative. 
 
THE UNFOLDING OF CONCEPTIONS. 75 
 
 15. Man == foot and horsemen. 
 
 16. Man = white, black, copper-colored, olive-colored, etc. 
 
 17. Thought = memory, conception, and reasoning.. 
 
 18. Poetry — didactic, lyric, and epic. 
 
 19. Poetry = didactic, lyric, epic, and the ballad and sonnet. 
 
 20. Matter = solid, liquid, aeriform, and radiant. 
 
 21. Duties to self = self-conservation, self-culture, and self-conduct 
 or direction. 
 
 22. Carnivora = cats, dogs, civets, weasels, bears, seals, whales, etc. 
 
 23. Mental faculties = sense-perception, memory, conception, ab- 
 straction, judgment, reasoning, and taste. 
 
 Section III.— Logical Definition. 
 
 Definition in general is the mental separation of an object 
 of thought embodied in language from every other object 
 of thought. Logical definition is the accurate unfolding of 
 the signification of the terms which embody thought. 
 
 The various forms of definition and the indefiniteness of 
 view on the whole subject of definition make it necessary 
 to consider with greater care, the kinds of definition and 
 the rules of logical definition. 
 
 Topic First. — The Kinds of Definition. 
 
 The word definition is used in both a w T ide and loose and 
 in a narrow and strict sense. For definition in the former 
 sense, Hamilton has suggested the name of declaration, 
 signifying throwing light upon, clearing up. It may also 
 be called rhetorical definition, in distinction from definition 
 in the narrow and strict sense, which is called logical 
 definition. 
 
 I. Rhetorical Definition. 
 
 The object of rhetorical definition or declaration is to 
 give the meaning of a word loosely, or as it is popularly 
 understood and for common use, rather than exactly and 
 for scientific ends. It does not necessarily undertake to 
 unfold essential properties, but freely uses those that are 
 
76 PRACTICAL LOGIC. 
 
 accidental, relative, or extrinsic. It is called description 
 when it makes use of a number of concrete characteristics, 
 as when we say that the Caucasian is tall, white, graceful. 
 
 1. Various popular modes of defining words may be in- 
 cluded under rhetorical definition. These should be dis- 
 tinguished in order to guard against certain common errors 
 and fallacies. 
 
 (1.) Etymological definition traces the root of a word 
 back to its origin and defines accordingly. It sometimes 
 throws much light upon the meaning of a word and adds 
 great force to the word. 
 
 There are, as has been shown by Trench in his " Study of Words," 
 most important lessons of history, romance, poetry, and morals wrapped 
 up in even our commonest words. In bringing out this meaning by 
 etymological definition it is necessary, however, to guard very care- 
 fully against two errors in particular, — that of fixing upon a wrong 
 etymology, and that of assuming that what the word meant at the 
 beginning it means now. Home Tooke furnished an illustration of 
 the first error in confounding the root of truth with that of trow, 
 meaning think, and then concluding that " truth is what onetroweth," 
 or simply a matter of opinion. A better philology finds for truth a 
 root which would make it signify reality. The second error may be 
 illustrated by assuming that villain is still simply a villager, because 
 that was the original meaning, or that knave is still merely a boy, 
 because that is what the word once meant. 
 
 (2.) Definition by word analysis, or by unfolding the 
 various roots of which a word is made up, bringing out 
 and combining their significations, — is also of value ; but, 
 since it involves, in most cases, a knowledge of the roots 
 of words, it is liable to lead to the same errors as etymo- 
 logical definition. 
 
 For example, the word edify, separated into its two component parts, 
 one meaning a temple and the other to make, would be defined etymo- 
 logically as the making or building of a temple. This may be strikingly 
 suggestive of the greater work of spiritual building signified by the 
 word as now used, but it can hardly be taken in the literal sense. 
 
THE UNFOLDING OF CONCEPTIONS. 77 
 
 Note.— The subject of word analysis is treated of in such works as Webb's 
 M Manual of Etymology," and Swinton's u Word Analysis." The student of 
 Logic ought to be familiar with it. 
 
 2. Rhetorical Definition may also proceed by the vari- 
 ous thought wholes, already considered. It may define 
 words, in the looser way, as essential, as mathematical, or 
 as logical wholes, by giving concrete characteristics, by 
 using synonymes, or by casual substitution of phrases. 
 
 Such careless definition sometimes takes the form of mere descrip- 
 tion, or the naming of one or more concrete characteristics, as when 
 we say, " Man is a risible animal," " Man is a two-legged animal 
 without feathers," " The east is where the sun rises." It sometimes 
 becomes only the enumeration of synonymes, as in much of the defi- 
 nition of the Dictionaries, as, " Law is a rule, decree, or statute," 
 " Religion is piety." It sometimes becomes little more than a careless 
 or casual substitution of phrases, narrative or descriptive, perhaps 
 presenting some consequence or attendant circumstance, as "Wisdom 
 leads to virtue and blessedness." 
 
 Some names are not definable except by rhetorical definition. It is 
 obvious that an individual cannot be logically defined, since practi- 
 cally we cannot form a notion comprising all the essential marks 
 which it has in common with any other notion or thing. Description 
 is the process applicable to individuals. On the other hand, simple 
 notions, or those containing a single or simple mark, cannot be logic- 
 ally defined, since they have only one mark and, therefore, no differ- 
 ential or distinguishing element. Being, for example, having only 
 one mark, existing, cannot be unfolded, as there is no complex content 
 to unfold. It can only be distinguished from nothing or non-entity, 
 which is a mere negation, or defined by some synonyme, as thing, 
 existence. 
 
 One office of Logic is to make plain the insufficiency of 
 all such loose forms of definition, while giving command of 
 the stricter forms of logical definition. 
 
 II. Logical Definition. 
 
 Logical definition separates a conception, as expressed by 
 a word, from all other conceptions by fixing upon and pre- 
 senting the essential and distinctive property or properties. 
 
78 PRACTICAL LOGIC. 
 
 1. Strict or perfect logical definition has two forms. — 
 
 The general term, as has been shown, may be considered 
 either as embodying a class or a concept proper, in other 
 words, either as a class term or as a concept term. Logical 
 definition should, therefore, regard the general term from 
 both these points of view. In other words, it is of two 
 forms : one defining the general term as a class term and 
 the other as a concept term ; the former dealing with extent 
 or contained objects, the latter with content or contained 
 properties. 
 
 Note.— The failure to recognize this twofold form has led to various differ- 
 ences of statement concerning the nature of logical definition. The old logical 
 definition was confined to the conception as a genus or class. Professor Davis 
 proposes to confine it to the conception as a concept proper. Logical definition 
 thus becomes substantially synonymous with Partition as that subject has 
 already been presented. Other logicians confine it to language or terms, and 
 make it apply chiefly to class terms. The view here taken is that it applies to 
 terms as embodying both classes and concepts. It is thus to be distinguished 
 from Logical Division and Partition, which deal with thought directly rather 
 than indirectly through language. 
 
 (1.) Definition of the Class Term. — If the term to be 
 defined is regarded or used as a class term, the definer is 
 required, by the principles of logical definition, — 
 
 First, to name the next higher genus to which the class, 
 considered as a species, belongs; and, 
 
 Secondly, to name the difference {differentia), or specific 
 difference or that which distinguishes the class, considered 
 as a species, from all the other co-ordinate species under 
 that higher genus. 
 
 The genus and difference together make up the essence 
 of the term, because they embrace the essential character- 
 istics or marks of the class embodied in the term. 
 
 Thus, in the definition, Man is a rational animal, it is meant that 
 animal is the next higher genus to which man belongs as a species, 
 and that rational is the difference or that which distinguishes man 
 from the other co-ordinate species, irrational animal or brute. 
 
 (2.) Definition of the Concept Term. — If the term to be 
 
THE UNFOLDING OF CONCEPTIONS. 79 
 
 defined is regarded or used as an attribute or concept 
 term, the definer is required, by the principles of logical 
 definition, — 
 
 First, to state the properties of the higher genus to which 
 the term, considered as a species, belongs ; and 
 
 Secondly, to state the properties which distinguish the 
 term, considered as a species, from other species under the 
 higher genus. 
 
 Thus, in the definition, Man is rational animal, the meaning is that 
 the concept term, man, includes animal properties or animality, and 
 rational properties or rationality. The properties of the higher 
 genus are included under animality, and those of the species under 
 rationality. 
 
 2. Certain imperfect forms of logical definition are also 
 distinguished by logicians. These are known as definition 
 by division, by colligation, by resolution, and by compo- 
 sition. They approach the strict standard of definition 
 more nearly than does rhetorical definition. They are in 
 fact statements of the results of Division and Partition. 
 
 The first two forms are simply different statements of the results of 
 Division as already treated. Definition by division unfolds a class 
 term into its constituent species or individuals, as when we state that, 
 " The animal kingdom consists of radiates, mollusks, articulates, and 
 vertebrates." Definition by colligation, which is the reverse of defi- 
 nition by division, gathers up and unites the constituent species or in- 
 dividuals of a genus or species, as when we say that, " The Earth, Mars, 
 Mercury, Venus, Jupiter, etc., are the planets." The second two forms 
 are simply different statements of the results of Partition as already 
 treated. Resolution brings out of a concept term its component prop- 
 erties, as when we say that, " Man is rational animal." Composition, 
 the reverse of resolution, gathers up and unites the component proper- 
 ties, as when we say that, " Rational animal is man." 
 
 3. By an extended process of logical definition an ulti- 
 mate and indefinable term is reached. In making such a 
 complete explication of a term it is necessary to proceed by 
 
80 PRACTICAL LOGIC 
 
 defining successively the genus of each new definition until 
 a simple notion is reached. 
 
 Professor Davis has illustrated this process in tabular form by an 
 extended definition of carnivore. 
 
 " A carnivore is a flesh-eating (—differentia) mammal (= genus). 
 A mammal is a vertebrate (= g) suckling its young (= d). 
 A vertebrate is an animal (= g) having an internal skeleton (=d). 
 An animal is a sentient (== d) organism (= g). 
 An organism is a living (= d) being (= g)." 
 
 The process comes to a close when the simple notion, being, is 
 reached. The result of the definition embraces all the properties con- 
 noted by the concept term, carnivore, and all that would be brought 
 out by a Partition of that term. Stated as a definition by resolution, 
 it becomes, "Carnivore includes flesh-eating, suck-giving, internal- 
 skeletoned, sentient, living, existing." 
 
 III. Nominal, Real, and Genetic Definition. 
 
 Logicians, from another point of view, distinguish defi- 
 nition as nominal, real, or genetic. The first has to do with 
 the mere name of the object of thought; the second with 
 its reality or essential properties ; the third with the cause 
 which generates it. 
 
 Nominal or verbal definitions, or definitions of names or words, 
 comprise the loose forms given under rhetorical definition or declara- 
 tion, as when we say, " The word circle signifies a uniformly curved 
 line." A real definition is a definition of the thought or reality em- 
 bodied in a word. It unfolds essential marks, and is, therefore, strictly 
 analytic. It comprises the forms of logical definition already given. 
 Thus we define a circle as "a line returning upon itself, of which all 
 the parts are equidistant from a given point." A genetic or causal 
 definition is one which states the rise or production of a thing as the 
 result of some working cause. It adds something to what is contained 
 in the defined term, and hence is always synthetic. The genetic defi- 
 nition of a circle is, " A circle is formed when we draw around, and 
 always at the same distance from, a fixed point, a movable point which 
 leaves its trace, until the termination of the movement coincides with 
 the commencement." Only such notions as relate to quantities repre- 
 
THE UNFOLDING OF CONCEPTIONS. 81 
 
 seated in space and time, in other words only mathematical notions, 
 can be genetically defined. 
 
 Topic Second. — The Rules of Logical Definition. 
 
 The rules for logical definition are determined by its 
 nature and aim. They spring either from peculiarities in 
 the origin and use of language, or from the nature of the 
 thought embodied in the language. 
 
 Rule 1st. — In logical definition the first step is to study 
 carefully the term to be defined. 
 
 The object of such study is to guard against the common 
 errors in defining, which arise from the ambiguities of lan- 
 guage. It is obvious, therefore, that logical definition 
 requires in general a knowledge of language and the prin- 
 ciples of interpretation. In particular it calls for a knowl- 
 edge of the kinds and sources of ambiguity in the use of 
 terms. 
 
 Professor Jevons has presented very forcibly the importance of a 
 thorough acquaintance with the great imperfections of language. He 
 says, " Comparatively few terms have one single clear meaning and 
 one meaning only, and whenever two or more meanings are uncon- 
 sciously confused together, we inevitably commit a logical fallacy. If, 
 for instance, a person should argue that ' punishment is an evil/ and 
 according to the principles of morality ' no evil is to be allowed even 
 with the purpose of doing good,' we might not at the first moment see 
 how to avoid the conclusion that ' no punishment should be allowed/ 
 because they are evil. A little reflection will sho~' thsk the word 
 evil is here xised in two totally different senses ; ia the fo.t case it 
 means physical evil or pain; in the second, moral evil; and because 
 moral evil is never to be committed, it does not follow that physical 
 evils are never to he indicted., for they are often fche very means of 
 preventing moral eviL" 
 
 In studying the subtle variations in the meaning of even 
 our common words, it is necessary to distinguish between 
 terms as uni vocal and equivocal. Univocal terms are those 
 which cajx suggest to the mind no more than a single mean- 
 
 F 
 
82 PRACTICAL LOGIC. 
 
 ing. Equivocal terms are such as have two or more differ- 
 ent meanings. 
 
 1. Strictly univocal terms are not liable to mislead. The names of 
 individual objects, persons, or events are usually fixed and certain in 
 their meaning, as George Washington, Westminster Abbey, the Atlan- 
 tic Ocean. The instances of univocal terms, outside of individual 
 names, are found chiefly in technical and scientific language. Steam- 
 engine, railway train, oxygen, hydrogen, sulphuric acid, etc., are 
 examples of what may be found in connection with every well-defined 
 science. It will be seen, however, on looking more closely, that gen- 
 eral terms are not strictly univocal. The same word has been found 
 to embody both the concept proper and the class. Hence the first 
 inquiry, even in the case of words commonly called univocal, should 
 be, Is the term here used as a concept term or as a class term f The 
 word man may be used in one case to express the attributes of human- . 
 ity, and in another to express the species or individual human beings, 
 and clear thinking requires that the thinker should know precisely 
 which is meant in any given case. 
 
 2. Equivocal terms are exceedingly numerous. Equivocal terms 
 are either properly ambiguous or homonymous. 
 
 (1.) A properly ambiguous (from Latin ambigo, to wander, hesitate, 
 or be in doubt) term is one that has come to be used in different sig- 
 nifications. Equivocation from ambiguity arises in two different ways : 
 
 1st. Through association, i. e., from the transfer of the meaning from 
 the thing originally denoted by the word to some other thing habit- 
 ually and intimately associated with it. The word church originally 
 denoted the building in which religious worshippers assemble. It 
 has come to mean the particular body of worshippers accustomed to 
 assemble in any one place ; or any body of persons holding the same 
 opinions and connected in one organization, as the Church of Eng- 
 land, the Roman Catholic Church ; or the church of Christendom ; or 
 the clergy and religious authorities of any sect or country. The word 
 differs entirely in meaning as used by a member of the Anglican, 
 Greek, Boman Catholic, Congregational, Presbyterian, or any other 
 existing church. 
 
 2d. Through analogy, i. e., from the transfer of meaning to analo- 
 gous objects. We speak of a sweet taste, a sweet flower, a sweet 
 tune, a sweet face, a sweet poem, from the analogy or resemblance 
 between the pleasure given by the flower, tune, etc., and that given 
 by something sweet to the taste, as a lump of sugar. 
 
THE UNFOLDING OF CONCEPTIONS. 83 
 
 The use of the same word in different significations renders it neces- 
 sary in many cases to ask the question, What is the signification in 
 which the word is here used? When the philosopher asserts that 
 11 experience proves the eternity of matter," the first question gives 
 rise to such as follow : Whose experience ? The philosopher's ? All 
 men's ? xill men's in all ages ? All human experience plus human 
 speculation ? 
 
 There are some ambiguous words which should be carefully studied 
 in order that an intelligent answer may be given to the question, 
 Precisely what does this word mean in the present instance f The word 
 all is an example of such ambiguity. In the proposition, " All these 
 soldiers are individual persons," all is used distributively, or one by 
 one. In the propositions, "Not all men are soldiers," "All men are 
 not soldiers," all with the negative attached is not equal to none, but 
 only to not some, so that the all in this case is only equal to some. 
 
 Words often change their meaning in the course of time, so that in 
 studying and testing the works of past thinkers, there is need to ask 
 the question, What ivas the meaning of the term to be defined, in the 
 day when this author wrote f When the authors of King James's ver- 
 sion of the Bible represent the Psalmist as prajnng, " Let thy tender 
 mercies speedily prevent us," careful inquiry should be made into the 
 use of the word prevent, about the opening of the seventeenth century. 
 Such inquiry will reveal the fact that the word, which now means to 
 go before one to hinder him, then meant to go before to anticipate or 
 supply his wants. 
 
 (2.) Homonyms are terms which, though of different origins, have 
 accidentally assumed the same form either in sound, or in spelling, or 
 in both. Examples of the first kind are seen in such words as right, 
 wright, write, rite, or rein, rain, reign, etc. Examples of the second 
 kind are such words as lead, the metal, and lead, as in following the 
 guidance of another. Examples of the third kind are such words as 
 mass, a heap, and mass, a Roman Catholic religious service. An im- 
 portant instance of this kind of equivocation is found in grammar, " as 
 between the numeral one, derived from an Aryan root, through the 
 Latin unus, and the indeterminate pronoun, one (as in, ' one ought to 
 do one's duty'), which is really a corrupt form of the French word 
 homme or man. The Germans to the present day use man in this 
 sense, as in, man sagt, i.e., one says." 
 
 Too great care cannot well be given to the study of the 
 terms to be defined. It is obvious, from the examples 
 
84 PRACTICAL LOGIC. 
 
 given, that any failure to grasp the precise signification in 
 which a single important word is used may utterly vitiate 
 a whole system of thought. 
 
 Rule 2d. — A logical definition should bring out the essence 
 of the term defined. This requires scientific accuracy. 
 
 The non-essential or accidental properties are not sufficiently charac- 
 teristic for a definition. The worthlessness of the well-known Platonic 
 definition, " Man is a two-legged animal without feathers," as contain- 
 ing only non-essential marks, was easily shown by Diogenes when he 
 presented a plucked chicken as Plato's man. 
 
 Since general terms embrace both concept and class, use 
 is to be made of both Partition and Division in framing 
 logical definitions. In the case of a class term the definition 
 should bring out the next higher genus, and the differentia, 
 or characteristic of the term defined considered as a species 
 under that genus. In the case of a concept term the defi- 
 nition should bring out the properties of the next higher 
 genus, and the differentia, or characteristics of the term 
 considered as the marks of a species under that genus. 
 
 Definition of the term as a class term is much the more common 
 form. Such definition becomes easy when the student has once learned 
 to put the term defined under the next higher class, and then to bring 
 out the distinguishing characteristics. Rhetoric is defined by first 
 putting it under the next higher class, art, or practical science, and 
 then distinguishing it from all other co-ordinate species of art by 
 stating its object, discourse, — "Rhetoric is the art of discourse." 
 Patriotism is defined by first putting it under the next higher class, 
 love, and then naming the special object, ones country, which distin- 
 guishes it from all other forms of love,—" Patriotism is love of one's 
 country." 
 
 Rule 3d. — A logical definition should be adequate or 
 precisely equal to the term defined. This forbids making 
 the definition too wide or too narrow, deficient or redundant. 
 
 It follows that a good definition may be tested by simple conver- 
 sion, or by letting the subject and predicate change places. If the 
 common definition, "Man is a rational animal," be adequate, then 
 
THE UNFOLDING OF CONCEPTIONS. 85 
 
 the converse will be true, " Every rational man is human." Strictly 
 speaking, we are not absolutely certain of the truth of this converse, 
 for although it may be true of this earth, there may be in other worlds 
 rational animals that are not men. The definition is, therefore, on 
 this supposition, said to be too wide, embracing not only man, but all 
 possible rational animals in other worlds. To make it perfectly ade- 
 quate it is necessary to add the relative property expressed by terres- 
 trial or some such term, as, " Man is a rational animal of this earth." 
 The converse will then be strictly true, " All rational animals of this 
 earth are men." On the other hand, if man be defined as spraying 
 animal, the definition is said to be too narrow. It is not true in the 
 strict sense that no animals that do not pray are men. The definition, 
 in other words, embraces only a part of men. Definitions are redun- 
 dant when they add to the essential characteristics derivative or unes- 
 sential marks, as, " Man is a rational animal that laughs;" they are 
 deficient when they omit some essential characteristic, as, " Man is an 
 animal." To the latter belong definitions by co-ordinate and subordi- 
 nate notions, as, "An odd number is that which is distinguished from 
 an even by unity," " Man is an American." 
 
 Rule 4th. — A logical definition should be expressed in 
 language as perfect as possible. 
 
 This forbids absurdity, ambiguity, verbosity, tautology, 
 and obscurity of language, as well as circular, negative, and 
 figurative definitions. 
 
 The language in a definition should be clear and signifi- 
 cant and not vague, ambiguous, or senseless. 
 
 When Mr. Spencer defines the virtue of patriotism as national 
 egoism, his definition is probably accepted by the mass of readers 
 without thought. But egoism is selfishness, which of course is not a 
 virtue at all, and patriotism is not a national but an individual senti- 
 ment. The definition is, therefore, absurd. The same objection holds 
 against Mr. Spencer's definition of evolution, " Evolution is a change 
 from an indefinite incoherent homogeneity to a definite coherent hetero- 
 geneity, through continuous differentiations and integrations." The 
 definition is pronounced obscure both by common readers and by those 
 who understand the strict meaning of the scientific and mathemati- 
 cal phraseology. A British critic has translated the definition into 
 English, as follows: " Evolution is a change from a nohowish untalk- 
 8 
 
86 PRACTICAL LOGIC. 
 
 aboutable-all-alikeness, to a somehowish and in-general-talkaboutable- 
 not-all-alikeness, by continuous somethingelsifications and stickto- 
 getherations." 
 
 The language in a definition should be precise and free 
 from surplus words. 
 
 Dr. Johnson's definition of oats, " Oats is a grain which in England 
 is generally given to horses, but in Scotland supports the people,'' vio- 
 lates this principle. The specific difference, expressed by the words 
 italicized, is entirely unessential. Dr. James, in the " Anxious In- 
 quirer," says, "It is a great principle that subjective religion, or in 
 other words, religion in us, is produced and sustained by fixing the 
 mind on objective religion, or the facts and doctrines of the word of 
 God." Euskin says of this, " Put entirely out the words I have put 
 in italics, and the sentence has a meaning, but by its verbosities it is 
 extended into pure nonsense; for 'facts' are neither ' objective' nor 
 4 subjective ' religion ; they are not religion at all. The belief of them, 
 attended with certain feelings, is religion ; and it must always be 
 religion *m us, 1 for in whom else should it be (unless in angels ; which 
 would not make it less subjective)." 
 
 The language in definition should not be tautological, 
 i. e. y a definition should not contain the name of the thing 
 defined, nor a derivative, synonymous, or correlative term, 
 for this would be to define a thing by itself. 
 
 This is violated by such definitions as " Life is the vital force." It 
 is also violated by what is called the circle or dialellon, as, "A board 
 is a thin plank," " A plank is a thick board." John Stuart Mill's 
 final definition of cause is a flagrant violation of this principle. It is 
 as follows : " We may define, therefore, the ca.use of a phenomenon to 
 be the antecedent, or concurrence of antecedents, on which it is*conse- 
 quent invariably, and subject only to the absence of preventing or 
 counteracting causes." The essential idea of cause, efficiency, is left 
 out ; the last and perhaps the most emphatic word in the definition of 
 cause is causes ; and the affirmation that the consequent is invariable 
 is followed immediately by the assertion of a variable condition. 
 
 The language in a definition should be perspicuous. 
 
 The aim of definition is to place the thought before the mind with 
 more distinctness ; hence, terms more unintelligible than the one de* 
 
THE UNFOLDING OF CONCEPTIONS, 87 
 
 fined should be avoided. This is violated by Aristotle's definition, 
 " The soul is the first entelechy or energy of a natural organized body 
 possessing life potentially." Definition by negative marks is also for- 
 bidden by this principle, where definition by positive marks is possible. 
 To define man as not a brute or not an angel gives no clear concep- 
 tion of what he is. Figures of speech are not ordinarily suitable for 
 definition, e. g., "Memory is the warder of the brain; " u The Divine 
 nature is a circle whose centre is everywhere and the circumference 
 nowhere." Such definitions make thought obscure rather than distinct. 
 
 Praxis.— Define the following terms Etymologically, by Analysis 
 (where possible), Rhetorically and Logically, stating the kind of Whole 
 in each case : 1. Proposition. 2. Development. 3. Sincere. 4. Lord. 
 5. Heathen. 6. Tawdry. 7. Saunter. 8. Slave. 9. Faculty. 10. Op- 
 eration. 11. Education. 12. Vulture. 13. Instinct. 14. Virtue. 
 15. Patriotism. 16. Fanaticism. 17. Ox. 18. Gas. 19. Ice. 20. Oxy- 
 gen. 21. Diamond. 22. Electricity. 23. Sun. 24. Moon. 25. Load- 
 stone. 26. Gold. 27. Sophomore. 28. Voyage. 29. Battle. 30. War. 
 31. Sentence. 32. Grammar. 33. Rhetoric. 34. Logic. 35. Arith- 
 metic. 36. Straight line. 37. Circle. 38. Point. 39. Sphere. 40. Vice. 
 41. Ghost. 42. Spirit. 43. Tribulation. 44. Passion. .45. Vexation. 
 46. Rage. 47. Love. 48. Desire. 49. Expectation. 50. Loafer. 
 
 Note.— See Trench " On the Study of Words." 
 
 Define the words from number 36 to number 39 inclusive, nominally, 
 really, and genetically. 
 
 Examine each of the following definitions, stating of what kind it 
 is, showing whether it conforms to the Rules, and, in case it does not, 
 showing wherein it fails, and correcting and completing it : 
 
 1. Grammar is the science of language. 
 
 2. Philology is the science of language. 
 
 3. A triangle is a rectilinear figure having three sides and three 
 angles. 
 
 4. A square is a quadrilateral having all the angles right angles, 
 all the sides equal, and the opposite sides parallel. 
 
 5. Malaria is that which induces fever. 
 
 6. A cone is a solid generated by the revolution of an angle about 
 one of its sides. 
 
 7. Virtue is a voluntary act done in obedience to the law of God for 
 the sake of everlasting happiness. 
 
 8. Logic is the art of reasoning. — Whately* 
 
88 PRACTICAL LOGIC. 
 
 9. Logic is the light-hou&e of the understanding. 
 
 10. Truth is the agreement of a cognition with its object. — Ham- 
 ilton. 
 
 11. Truth is accordance with the reality. 
 
 12. A whale is a large fish inhabiting the polar seas, and furnishing 
 oil and whalebone as articles of commerce. 
 
 13. Happiness is the reflex of unimpeded energy. — Hamilton. 
 
 14. Life is that condition of an organized being in which it is 
 capable of performing its functions. — Porter. 
 
 15. Life is definable as the continued adjustment of internal rela- 
 tions to external relations. — Spencer. 
 
 16. Science is systematized knowledge. 
 
 17. Mind is the unextended.— Bain. 
 
 18. Matter is the permanent possibility of sensation. — Mill. 
 
 19. Mind is a conscious string of sensations. 
 
 20. A sphere is a solid generated by a revolution of a semicircle 
 about its diameter as an axis. 
 
 21. A sphere is a solid or volume bounded by a surface, every point 
 of which is equally distant from a point within, called the centre. — 
 Worcester. 
 
 22. Education is the training of the intellectual powers, principally 
 by the study of the physical sciences. 
 
 23. Knowledge is power. 
 
 24. Net-work is anything reticulated or decussated at equal dis- 
 tances with interstices between the intersections. — Dr. Johnson. 
 
 25. A saunterer is one who is going to the Holy Land. 
 
 26. Law is a lawful command. 
 
 27. Gratitude is a lively sense of future favors. 
 
 28. Gratitude is a virtue of acknowledgment. 
 
 29. A ruler is one who establishes laws. 
 
 30. A circle is a curved line returning upon itself, the parts of which 
 are at an equal distance from the central point. 
 
 31. Logic is the electric light of the intellect, the cynosure of truth, 
 the physic of the mind. 
 
 32. Man is an animal walking on two feet. 
 
 33. Man is a bimanous mammal. 
 
 34. Monarchy is a form of political government in which one man 
 is sovereign. 
 
 35. Wealth is that which furthers the well-being of man. 
 
 36. The soul is the principle by which we live, feel, move, perceive, 
 and understand. — Aristotle. 
 
THE UNFOLDING OF CONCEPTIONS. 89 
 
 37. Beauty is the feeling we experience in recognizing nnity amidst 
 variety. 
 
 38. A dragon is a serpent breathing flame. 
 
 39. Fine Art is the embodiment of thought in sensuous form. 
 
 40. Man is a rational being. 
 
 41. A cat is a domestic animal. 
 
 42. A dog is a digitigrade quadruped, having fixed claws, four toes, 
 and a recurved tail. 
 
 43. Memory is that power of the human soul which recalls past 
 knowledge. 
 
 44. Philosophy is the science of principles. — Ueberweg. 
 
 45. Philosophy is the love of wisdom. 
 
 46. Dirt is matter in the wrong place. — Lord Palmerstok. 
 
 47. A perception is an impression made on the mind. 
 
 48. Mathematics is the science of extension. 
 
 49. Snow is frozen mist. 
 
 50. A carnivore is flesh-eating, suck-giving, internal-skeletoned, 
 sentient, living, existing. 
 
 51. A seal is a species of fish. 
 
 52. Honesty is a species of policy distinguished from other co- 
 ordinate species by being the best. 
 
 53. Dancing is a refined and sublimated modification of circum- 
 ambulatory locomotion. 
 
 54. Man is physically a living machine. 
 
 55. A conjunction is a word that connects words and sentences. 
 
 56. Matter is that in which is discerned the promise and potency of 
 all terrestrial life. — Tyndall. 
 
 57. God is the not-ourselves which makes for righteousness. — Mat- 
 thew Arnold. 
 
 58. Religion is cosmic emotion. — Clifford. 
 
 59. Evolution or development is essentially a combination of causes 
 working toward a particular end. — McCosh. 
 
 60. The conic section is that mathematical figure which divides into 
 these four forms — circle, ellipse, parabola, hyperbola. 
 
 61. The sensibility takes that to be good which warrants or prom- 
 ises pleasure, and affects us pleasantly ; — the desires rest on pleasant 
 feelings. 
 
 62. The feeling of the pleasant is the immediate consciousness of 
 the furtherance of life. — Ueberweg. 
 
 63. Justice is a square number. 
 
 64. The idea of the good is the sun in the kingdom of ideas. — Plato. 
 
 8* 
 
90 PRACTICAL LOGIC. 
 
 65. Nature (Heaven and earth and all that is therein) is the body 
 of God. 
 
 66. The state is man writ large. 
 
 Define the principal Terms used in the following Sciences, testing 
 the definitions by the Rules: 1. Arithmetic. 2. Geometry. 3. Botany. 
 4. Zoology. 5. Grammar. 6. Physical Geography. 7. Rhetoric. 8. Psy- 
 chology. 9. Natural Philosophy. 10. Astronomy. 11. Geology. 12. Eth- 
 ics. 13. Political Economy. 14. Science of Government. 
 
 o>*o 
 
 SUMMARY OF RESULTS 
 
 The aim of the Logic of Conception is to train to the 
 best thinking and fullest appreciation of thought in the 
 first form. The degree of perfection or imperfection with 
 which the mind grasps its conceptions constitutes what is 
 called the logical quality of conception. Our grasp of con- 
 ceptions is perfect in proportion as it is clear, distinct, and 
 adequate : imperfect in proportion as it is obscure, confused, 
 and inadequate. 
 
 A conception is clear when it is simply distinguishable from others ; 
 obscure when it is not. This may be illustrated by experience in 
 gazing upon a tree. When the light falls upon it w© readily distin- 
 guish it from other trees and objects of the landscape, and the view is 
 clear ; but when the mist or the twilight settles around it we can no 
 longer distinguish it from other objects, and the view becomes obscure. 
 We have a clear conception of man when we distinguish it from inor- 
 ganic matter, plant, animal, etc. ; so long as we are unable to do this 
 our conception of it is obscure. 
 
 A conception is distinct when we not only distinguish its object 
 from all others, but also grasp the constituent marks or parts of that 
 object. In every-day life we may know the hand-writing or features 
 of a person from those of all others and yet not be able to give the 
 characteristics of either. This is true in conception, — we may be able 
 to discriminate man from mineral, plant, animal, etc., and yet not be 
 able to give the characteristics of man. Our conception is confused or 
 indistinct. Distinctness requires us not only to discriminate between 
 
THE UNFOLDING OF CONCEPTIONS. 91 
 
 an object and all others, but also to know the distinctive marks or parts 
 of that object. Our conception of man becomes distinct when we see 
 that it includes animality, rationality, and terrestriality ; until then 
 it is confused. 
 
 A conception is adequate when we not only grasp the constituent 
 marks, but also the marks of these marks ; inadequate when we fail 
 to do this. Perfect adequacy of conception is reached by carrying out 
 the complex processes of Partition, Division, and Definition until the 
 lowest component attributes, constituent species, and characteristic 
 marks are reached. The extent to which these processes must be car- 
 ried to reach a practical adequacy of conception in any given case will 
 depend upon the exigencies of the thinking or the aims of the thinker. 
 The conception of man is adequate when we not only know the three 
 marks given above, but have also gone further and grasped the marks 
 of animality, as corporeity, organization, life, sentiency, voluntary 
 motion; of rationality, as intuition of first truths and the power of 
 thinking and acting in the light of such truths ; of terrestriality , as 
 limitation to the earth with its conditions of time and space. 
 
 It will be readily seen that clearness is chiefly attained 
 through Definition ; distinctness through Partition and 
 Division ; adequacy through the extended processes of Par- 
 tition, Division, and Definition. 
 
 A conception is true when it corresponds with the reality. 
 The aim of the Practical Logic of conception is fully at- 
 tained when the training results in the ability of the thinker 
 to reach true conceptions which are clear, distinct, and 
 adequate. 
 
Part II. 
 
 THE LOGIC OF JUDGMENT OR THE PROPOSITION. 
 
 The aim of the Logic of Judgment is to train the mind 
 to skill in dealing with the second Form of Thought. 
 
 Definition. — Judgment is that form of thought in which 
 we compare two notions and mentally affirm their union or 
 disunion, on the ground of a like union or disunion appre- 
 hended in the objects or realities which the notions repre- 
 sent. The result of the operation of judging is a complex 
 form of thought known as a Judgment, the verbal expres- 
 sion of which is called an Assertion or Proposition. The 
 connection between judgment and proposition is so intimate 
 that the two terms are used interchangeably. 
 
 Note.— The definitions of judgment have been various. Some have defined 
 it to be, the affirmation of the agreement or disagreement, or of the congruence 
 or connection, of two notions. According to Thomson, it is " an expression 
 that two notions can or cannot be reconciled— that the mark of the one may 
 or may not henceforward be assigned to the other." Manifestly judgment as 
 thought is much more than mere affirmation, whether mental or verbal, of the 
 agreement or disagreement of two notions. The question whether the form 
 of words, "Man is intelligent/' or, " Man is patent elliptic," is a judgment or 
 embodies a judgment, is not to be decided by affirmation of any kind. It de- 
 pends upon the knowledge of connection existing or not existing between the 
 realities or objects represented by the words and notions. 
 
 Ueberweg comes nearer the presentation of the essence of judgment, when 
 he makes it the comparison of two notions, whose forms are different from 
 but belong to each other, and the mental affirmation of their union or disjunc- 
 tion on the ground of like relation apprehended between the objective realities 
 
 92 
 
THE FORMATIOX OF JUDGMENTS. 93 
 
 which the notions represent. The all-important thing is "the consciousness, 
 whether or not the analogous combination exists between the corresponding 
 objective elements. As the individual conception corresponds to the individ- 
 ual existence, so the judgment in its various forms corresponds to and is the 
 subjective copy of the various objective relations." 
 
 The desired skill in judgment can only be acquired by 
 the knowledge and use of the principles which govern the 
 forming and unfolding of judgments. The subject will, 
 therefore, be considered under two Chapters, one treating 
 
 of the formation of judgments, the other of their unfolding. 
 
 CHAPTER I. 
 
 THE FORMATION OF JUDGMENTS OR 
 PROPOSITIONS. 
 
 The formation of judgments is manifestly a most imrjor- 
 tant work of thought. Processes of reasoning and systems 
 of science and philosophy are made up of combinations of 
 judgments, and if the judgments are not properly and 
 thoroughly established, i. e., if they are not true, then the 
 arguments and systems cannot be expected to prove true. 
 It is, therefore, necessary to inquire carefully into both the 
 process and products of judgment-forming. 
 
 Section I.— The Process of Judgment-Ponning. 
 
 The definition of judgment already given suggests for 
 consideration the following Topics : first, ascertaining and 
 combining the elements of judgment ; second, finding the 
 
 reasons or grounds upon which the truth of judgments de- 
 pends, or the verification of judgments. 
 
 Topic First. — The Elements of Judgment. 
 
 The elements of judgment are ascertained by analyzing 
 judgment either as embodied in the proposition or as a 
 form of thought. From the former point of view, it is 
 
94 PRACTICAL LOGIC. 
 
 made up of two terms (so called because they are the ter- 
 mini or boundaries of the proposition) united by the verb 
 to be as copula {bond) ; from the latter point of view, it is 
 composed of two notions united by some connecting link of 
 thought. 
 
 I. The Terms or Notions in Judgment. 
 
 The terms or notions are distinguished as the Subject or 
 Subject Notion, or that about which the assertion is made, 
 and the Predicate or Predicate Notion, or that whose union 
 or non-union with the subject is affirmed. In logical form- 
 ulae the subject is usually expressed by S and the predicate 
 by P. 
 
 The various notions, already considered, resulting from the processes 
 of conception, constitute the material which may possibly form the 
 terms of judgments. The following kinds have already been distin- 
 guished : (1.) The simple notion, called also simple apprehension, and 
 percept. This is the result of immediate cognitions by the senses 
 and consciousness. In observation this notion has as yet no name 
 given, but may be known by the indefinite "it." An orange, as an 
 object hitherto unseen and unknown, might be called "it." (2.) The 
 simple abstract notion, or part abstracted from the object observed, 
 but not yet combined with others into a concept. By observation we 
 get, from the hitherto unseen and uninvestigated orange, the abstracts, 
 yellow, round, sweet, juicy, etc. (3.) The general notion, as the con- 
 cept proper or bundle of properties or marks expressed in the concept 
 term. By conception proper the various abstracted properties are 
 gathered up in thought in the concept, orange. (4.) The general no- 
 tion, as the class or group of objects to which the bundle of attributes 
 in the concept applies. By classification the concept orange is applied. 
 
 It will be seen that only part of these can enter into the strictly 
 logical judgment. 
 
 II. The Connecting Links of Judgment. 
 
 The two terms of a proposition are always united by the 
 copula, which, according to the view of most logicians, is 
 always the present tense indicative of the verb to be, either 
 with or without the negative particle. The real quality of 
 
THE FORMATION OF JUDGMENTS. 95 
 
 judgment, however, or that which makes it what it is, is 
 the mental union or separation of two terms or notions, on 
 the ground of a more or less clearly apprehended connec- 
 tion or absence of connection between them. The various 
 links by which this union in judgment is affected are to be 
 found in the predicables already given. 
 
 1. While the connecting link of judgment in language is 
 always the verb to be, which to the logician signifies connec- 
 tion rather than existence, it is obvious that the copula does 
 not always appear in this form in propositions as w T e find 
 them. E. g., 
 
 " Columbus discovered America ; " " Napoleon was the emperor of 
 France." Hence arises the necessity for the practical application of 
 the Second Logical Postulate, in reducing judgments to the normal 
 form, S is P, or S is not P. Under this any change of logical form is 
 permissible, provided it brings out the thought more fully, without 
 changing it. "I am," means "I am existing," or, "I am a being." 
 11 Columbus discovered America," means, u Columbus is the one who 
 discovered America." " Napoleon was the emperor of France," means, 
 " Napoleon is he who was the emperor of France." " Stars twinkle," 
 means, " Stars are things that twinkle." The same postulate permits 
 the restoration of all inversions and displacements of parts of sen- 
 tences to the normal form, S is P, or S is not P. E. g., " Great is 
 Diana of the Ephesians " becomes " Diana of the Ephesians is great." 
 
 2. A judgment, however, is not a mere form of words, 
 two terms joined by the verb to be. " Man is intelligent." 
 V Man is round-square horizontal." One of these is a judg- 
 ment ; the other is not. The difference is that in the one 
 case there is a connection in thought, while in the other 
 there is none. This connection has been variously pre- 
 sented, 
 
 (1.) It has been said that the affirmative judgment is 
 always based upon the Axiom of Identity ; the negative on 
 the Axiom of Contradiction. In accordance with this view 
 judgment has been defined to be the affirmation of agree- 
 ment or disagreement. 
 
96 PRACTICAL LOGIC 
 
 This is true, but it is necessary to go below these generalities to the 
 special features in which the agreement or disagreement is found. E. 
 g., in the judgment, " Man is a terrestrial, rational animal," the copula 
 represents equality or identity. This is true in all perfect definitions. 
 Or again, in the judgment, " Man is intelligent," the copula expresses 
 the relation of substance and property, or genus and species, and the 
 judgment is interpreted as meaning, either that intelligence is an attri- 
 bute of humanity, or that man is a species of the genus intelligent 
 beings. Or again, in the judgment, " The life was the light of men," 
 the copula may express the relation of substance and active property 
 or cause and effect. The judgment is thus seen to involve certain spe- 
 cial principles of connection which underlie the mere agreement or 
 disagreement. 
 
 (2.) According to the Aristotelian logic, every judgment predicates 
 of the subject either a genus, or a property, or a definition, or an 
 accident. 
 
 These forms of predication have been illustrated by suitable judg- 
 ments. " Envy is a passion." The relation is that of genus to species. 
 " Man has the faculty of speech." The relation is that of peculiar 
 property to substance or subject. " A state is a community governed 
 by its own laws." The relation is that of identity of the essential 
 properties, or essence of a thing,— by which the definition is consti- 
 tuted, — with the thing itself. " Life is sweet." The relation is that 
 of an accidental property to its subj ect. 
 
 These predicable classes have been reduced by Thomson to definition 
 and attribute, the latter including genus, property, and accident. 
 
 (3.) The Predieables as given, page 30, furnish the sim- 
 plest statement of what may be predicated in any judgment. 
 Of any subject may be predicated its substance and what- 
 ever belongs to it as its properties. 
 
 Thus of man may be predicated the substance of the thing itself, 
 as " Man is man ; " or some of the properties of quality, as " Man is 
 rational," or all of them (the essence or definition), "Man is rational 
 animal ; " or active properties, as " Man is the moulder of nature ; " or 
 relative properties, as " Man is of few days," " Man is terrestrial," 
 " Man is finite," etc. 
 
 When notions or terms are thought together by one or 
 other of these various connections the product is a judgment. 
 
THE FORMATION OF JUDGMENTS. 97 
 
 III. The Elements Combined. 
 
 The various notions or terms are united either in judg- 
 ments of observation or in strictly logical judgments. 
 These are both included under logical judgments in the 
 wider sense. 
 
 Note. — Hamilton gives the name of primitive judgment to the judgment of 
 existence implied in all our cognitions. This is not, however, judgment as thought, 
 and, therefore, is not to be treated in Logic. 
 
 1. The judgment of observation follows upon observation. In start- 
 ing with, an orange, assumed to be a thing never before known, the 
 observer has no name for the object. The mental analysis by which 
 the abstracts are formed may be looked upon as made up of a succes- 
 sion of judgments : " It is yellow ; " " It is sweet ; " " It is round ; " 
 etc. All the predicates of these judgments, when gathered up, give 
 the concept, which is finally embodied in the word orange, and then 
 used in classifying all like objects as oranges. The judgment of obser- 
 vation may be seen to be the mental union of simple apprehensions 
 or percepts and abstracts. 
 
 2. The judgment of observation thus prepares the way for and 
 gradually approaches the strictly logical judgment, which makes use 
 of the concept and class, as, " The orange is yellow; " " Oranges are 
 yellow." It will readily be seen that the strictly logical judgment 
 will take different forms, as the subject and predicate are concept or 
 class notions. The various relations of the notions in logical judg- 
 ments as embodied in propositions may be brought out in the following 
 form, using the notions man and mortal : 
 
 Subject. 
 
 Copula. 
 
 Predicate. 
 
 Concept proper, 
 
 
 Concept proper 
 
 ( Man = humanity) 
 
 f is ) 
 
 (mortal.) 
 
 Class, 
 
 or 
 
 Class, 
 
 (Man = mankind) 
 
 I is not ) 
 
 (a mortal.) 
 
 The strictly logical judgment is the form of judgment of 
 which Logic mainly treats. In the logical proposition the 
 two terms may both be concept terms, giving a proposition 
 of content, as, " Man is mortal ; " or both class terms, giv- 
 ing a proposition of extent, as, " Man is a mortal." 
 
 The subject term in the latter form may be either an individual, as, 
 9 G 
 
98 PRACTICAL LOGIC 
 
 "Garibaldi;" or an individualized general term, as "this man;" or 
 a general term taken partially, as " some men ; " or a general term 
 taken universally, as " all men." This form of logical judgment may, 
 therefore, be either, " Garibaldi is mortal," or " This man is mortal," 
 or " Some men are mortal," or " All men are mortal." 
 
 Note.— The strictly impersonal judgments, expressed in the classical lan- 
 guages without subject (except as the subject in the third person singular is 
 involved in the termination of the impersonal verb) and in the English with 
 " it" as the subject, as, " it rains," " it thunders," properly come under the logi- 
 cal judgments. Says Ueberweg, " In the so-called judgments without subjects 
 the sum total of the existence surrounding us, thought of indefinitely, or an 
 indefinite part of it, takes the place of the subject." 
 
 Praxis. — Examine carefully the following judgments, stating them 
 in the normal form (S is P, or S is not P), naming the subject and 
 predicate, and bringing out the precise connecting link in each case : 
 1. Truth is stronger than error. 2. The human race was one in its 
 origin. 3. A square is rectangular. 4. A square is an equilateral 
 rectangle. 5. "Few and short were the prayers we said." 6. 
 " Flashed all their sabres bare." 7. Man is risible. 8. Not all the 
 ills of earth can mar my joy. 9. Not all men are virtuous. 10. A 
 horse may be white. 11. He that destroys a usurper does right. 12. 
 Great is the work of life. 13. There was no possibility of substan- 
 tiating the allegations. 14. " In jewels and gold men cannot grow 
 old." 15. "From peak to peak the rattling crags among leaps the 
 live thunder." 16. It is wrong to put an innocent man to death. 
 17. There is no place like home. 18. "None but the brave deserve 
 the fair." 19. " The most sublime act is to put another before thee." 
 20. Life every man holds dear. 
 
 Topic Second. — Verification or Proof of Judgments. 
 
 When a so-called judgment, expressed in a proposition, 
 is brought before the mind, the question is naturally asked 
 concerning it, What reason is there for believing it to be 
 true? A so-called judgment is decided to be true, doubt- 
 ful, or false, by the presence or absence of proof, i. e., of 
 something which makes the reality of the connection of the 
 two notions more or less evident to the mind. 
 
 Practically, in all our intercourse with men and books, judgments 
 of every form are constantly being presented to our minds for con- 
 
THE FORMATION OF JUDGMENTS. 99 
 
 sideration. " Geometry is the science of extension." " Things which 
 are equal to the same thing are equal to each other." " Logic is the 
 art of reasoning." " The weather is cold." " If the weather remains 
 as at present, the streams will be frozen over." In short, every sen- 
 tence read, heard, or uttered involves one or more judgments, and no 
 such judgment is anything more to us than an empty assertion until 
 we have grasped some proof that the expressed connection of its parts 
 agrees with the corresponding reality. The verification or confirmation 
 of judgments is, therefore, a most important part of this form of thought. 
 
 Judgments have been divided, by the sources from which, 
 the predicate is drawn, into analytic and synthetic. The 
 predicate notion may either be brought out of the subject 
 notion by analysis, or brought to it from without. Proofs 
 are accordingly either analytic or synthetic, the former 
 being drawn by analysis from the terms of the proposition 
 itself; the latter being brought from outside the terms of 
 the proposition. 
 
 An analytic or explicative judgment is one in which what is affirmed 
 in the predicate is already contained in the definition of the concept 
 or general term which forms the suhject. " Man is rational," is an 
 analytic judgment ; since the predicate, rational, is involved in the 
 notion, man, as brought out by partition or by the definition, " Man 
 is a rational animal." Such judgments are also called a priori, or 
 judgments not grounded on but prior to experience. The simple study 
 of what is contained in the subject notion gives the predicate without 
 resort to the testimony of experience. E. g., in the judgment, " Body 
 is extended," the instant the thinker understands what is meant by the 
 term "body," he knows that " extended" is comprehended in it. A 
 synthetic or ampliative judgment is one in which the predicate adds 
 something which is not contained in the conception or definition of the 
 subject. E. g., "Man is a sinner," "Neptune is the most remote of 
 the planets," are synthetic judgments. The predicate adds to the 
 subject something which it brings from outside and which no analysis 
 could have discerned in the subject. 
 
 In connection with the various forms of judgment analytic 
 and synthetic the nature of the proof, and the canons or 
 rules governing it, will be set forth. 
 
100 PRACTICAL LOGIC. 
 
 I. Proof of Analytic Judgments. 
 
 Analytic judgments furnish within themselves the ma- 
 terial for their own verification. This is to be brought out 
 by analysis, i. e., by partition or division of the subject or 
 predicate or both. 
 
 The proposition, "All trees are organic," is proved by analyzing 
 "organic." The proposition is regarded as one of extent, affirming 
 that the genus, " organic beings " includes the species, " trees." Or- 
 ganic beings are divided, by the presence or absence of a nervous sys- 
 tem and power of causation, into animals and plants. Plants are 
 divided, by the size and duration of the stem or ascending axis, into 
 herbs, shrubs, and trees. The result reached may be expressed in tab- 
 ular form : 
 
 Organic beings = < Animals, / Herbs, 
 I Plants == \ Shrubs, 
 ( Trees ; 
 
 froDi which it is apparent that the lower species " trees " is included 
 under the higher genus " organic." The proposition, w Duelling is 
 murder," is analytic. Regarded as a proposition of content, its proof 
 is reached by partition of the terms. " Murder " includes the generic 
 mark, taking of human life, and the differential or specific marks, de- 
 liberately, unlawfully, maliciously. "Duelling," where it results in 
 death, is found to include the same marks, taking of human life, de- 
 liberately, unlawfully, maliciously. The two are thus found to agree. 
 Duelling is, therefore, murder, i. e., the relation affirmed to exist between 
 the two, in the proposition to be proved, corresponds to the reality. 
 The proof of the proposition, " Labor is a blessing to man," is to be 
 found by an analysis of the terms. Eegarded as a proposition of ex- 
 tent, it affirms that "labor" is one species of the genus or class 
 "blessings to man." By partition "blessing to man" has the active 
 properties or characteristics, meeting some fundamental and natural 
 need of man, giving satisfaction or happiness. There are, therefore, as 
 many " blessings to man " as he has fundamental and legitimate needs 
 to be satisfied. Analyzing " blessings to man " by division, we, there- 
 fore, find that the genus includes the desires for habitual activity 
 physical and rational, for knowledge, for power, for property, for help 
 in dependence and helplessness, for deliverance from sin, etc. Any- 
 thing which meets and satisfies any one of these desires is a blessing 
 
THE FORMATION OF JUDGMENTS. 101 
 
 to man. " Labor " analyzed by partition is found to include the 
 marks, exertion of the powers, habitual, with rational aim, or, in other 
 words, habitual rational activity. " Labor," as meeting the funda- 
 mental and legitimate need for habitual rational activity is a " blessing 
 to man." Continuing the process of thought still further, we may 
 conclude from the analysis, that "knowledge" is a blessing to man, 
 "power" is a blessing to man, "wealth" is a blessing to man, "the 
 sustaining power of divine providence" is a blessing to man, "sal- 
 vation from sin " is a blessing to man, etc. 
 
 General Rule. — The analysis must be accurate and com- 
 plete. 
 
 It is obvious that this method of proof must render cer- 
 tain the truth of the propositions which admit of its appli- 
 cation. All analytic proof is, therefore, said to be demon- 
 strative in its force. 
 
 II. — Proof of Synthetic Judgments. 
 
 Synthetic judgments require that their proofs be sought 
 outside of the judgments themselves. No analysis of terms 
 will furnish the proof that, " Duelling is a relic of barbar- 
 ism," or that, " The Feudal System was beneficial." The 
 proof must be brought from outside sources. 
 
 The precise source or place outside will depend upon the 
 species of synthetic judgment to be proved. Synthetic 
 judgments are divided, by the place outside the proposition 
 from which the predicate is brought, into intuitive and em- 
 pirical. 
 
 Intuitive, or a priori, judgments are those whose predicates are 
 brought from within the mind itself, from some fundamental or thought 
 necessity. In these the predicate could never be unfolded from the 
 subject, as in the judgment, " Every event must have a cause." It is 
 a law of our thinking that compels us to connect " must have a cause " 
 with the subject, " every event." Empirical, or a posteriori, judg- 
 ments are those of which the predicates are brought from outside the 
 mind. They have their ground in experience. The judgment, " Body 
 is extended substance," is analytic, since " extended substance " is seen 
 to be comprehended in "body," or to be identical with it; but the 
 9* 
 
102 PRACTICAL LOGIC 
 
 judgment, M Body is heavy," is a synthetic judgment, since the mark 
 " heavy " is not comprehended in " body." The latter is an empirical 
 judgment, since only experience, examining bodies and measuring 
 pressure by muscular effort, enables us to predicate " heavy " of " body." 
 
 1. Proof of Intuitive Judgments. — These draw their 
 proofs from the mind itself. The proofs are intuitions or 
 fundamental truths, accepted by all, and lying at the foun- 
 dation of all human knowledge and activity. 
 
 For the proposition, " Suicide is wrong, " the proof is to be found 
 in man's intuitive convictions of duty. Every one knows intuitively 
 that man, as a creature under the moral government of God, is bound 
 to make the most and the best of himself, and that to fail in this is 
 wrong. Duty is intuitively seen to require that he should preserve 
 himself, improve himself, and use his powers for the true end of life. 
 11 Suicide " is intuitively seen to break the first of these requirements, 
 and, therefore, seen to be " wrong." The propositions, " I exist," " I 
 am thinking," rest upon the intuitive belief in the veracity of our 
 consciousness. 
 
 As so-called intuitions are often urged in proof of various 
 false judgments, it becomes necessary to keep clearly in 
 mind the tests of intuition. These may be given in the 
 following rules : 
 
 Rule 1st. — Every intuition is self-evident. The mind, on the bare 
 contemplation of it, must see its truth at once, without requiring any 
 foreign evidence or outside proof. 
 
 Rule 2d. — Every intuition is necessary. The mind cannot help be- 
 lieving and acting upon its truth. That "Space exceeds my widest 
 imagination of space," and that " Every event must have a cause," 
 one cannot help believing. 
 
 Rule 3d. — Every intuition is catholic or universal. It must be en- 
 tertained by all men intelligent and understanding what is meant by 
 it. An intuition is sometimes described as being " What all men 
 everywhere and always believe." 
 
 Rule 4th. — Every intuition is accepted by all men practically. In- 
 tuitive truths may not be consciously apprehended and stated by the 
 majority of mankind, but they are assumed and acted upon by all 
 men, even by those who deny their belief in them. 
 
THE FORMATION OF JUDGMENTS. 103 
 
 The notions of being, personal identity, time, space, causation, the 
 axioms of Mathematics, Logic, Ethics, etc., are among these self-evi- 
 dent, necessary, and universal cognitions of men. 
 
 It is evident that all such proofs, properly tested, must 
 render certain the trutji of propositions based upon them. 
 Intuitive proofs are, therefore, said to be, like analytic 
 proofs, demonstrative in force. 
 
 2. Proofs of Empirical Judgments. — Empirical judg- 
 ments, or those based upon something outside of the propo- 
 sition and of the mind itself, rest for their proofs upon the 
 experience of the thinker himself or of others. Knowledge 
 in the form of experience has been seen (p. 16) to include 
 the observation and thinking of the man himself, and the 
 observation and experience of others given in testimony 
 and authority. This suggests the kinds of empirical judg- 
 ments to be established. 
 
 (1.) Judgments from Observation. — When the judgment to be veri- 
 fied is based upon our own observation of things external or internal, 
 its truth is tested by careful application of the Rules of Observation 
 already given (p. 33). Thus, " I see my uplifted hand in all its parts-, " 
 " I am conscious of exertion in lifting my hand," are judgments of 
 observation. Their truth evidently depends upon the trustworthiness 
 of the senses and consciousness, assumed in all observation, and upon 
 strict compliance with the Rules of Observation. 
 
 (2.) Judgment from Thought. — Many empirical judgments are 
 reached by the processes of Reasoning Inductive and Deductive. 
 These must be tested by the Canons oi Reasoning, which will be 
 presented in Part III. 
 
 (3,) Judgments from Testimony and Authority. — Testi- 
 mony is the statement of others concerning matters of fact 
 which they have observed in their own consciousness or in 
 the world around them. Authority is the statement of 
 others concerning matters of opinion which they have 
 reached by the processes of conception, judgment, and rea- 
 soning. The testimony or authority may be recorded on 
 
104 PRACTICAL LOGIC. 
 
 monuments or in writings, books, etc., or given by word of 
 mouth. 
 
 As almost all human knowledge is received on testimony 
 or authority, the question, What are the tests of testimony 
 and authority ? becomes a most important one. The tests 
 are to be found either, first, in the ability, character and 
 number of witnesses or authorities, or, secondly, in the 
 character of that which they present. Out of these arise 
 the Rules to be observed in judging of the truth or falsity 
 of judgments received from others. 
 
 Eule 1st. — A witness or authority must be competent, 
 i. e, t must have the opportunity, the ability, and the dispo- 
 sition to know the facts testified to, or to think out the 
 judgments presented on his authority. 
 
 a. Want of opportunity to observe destroys the value of any so- 
 called testimony. The testimony of A concerning what B says that G 
 did is mere hearsay, and of little evidential valne. Negative testi- 
 mony is of little value. The testimony of a thousand witnesses that 
 they did not see A kill B is not sufficient to countervail the statement 
 of one good witness that he did see A kill B. Want of ability to ob- 
 serve the facts in any given case may make the testimony worthless. 
 A blind man's testimony to mere objects of sight is worthless. Cer- 
 tain spheres of observation require special skill, so that only the testi- 
 mony of experts, or those trained for the purpose, may be of value 
 in those spheres. A man acquainted with the phenomena of electricity 
 will be able to detect important facts which would entirely escape the 
 notice of the ordinary observer. Testimony regarding the distance, 
 size, form, and appearance of any object requires a trained judgment 
 to make the observation trustworthy. Thus the testimony of an ex- 
 pert, — e. #., of a practical astronomer to the fall of a meteor, — may 
 become of more value than that of hundreds of ordinary observers. 
 Want of disposition to observe accurately vitiates testimony. This 
 may result, through habitual carelessness, in imperfect observation, or, 
 through prejudice, in warped views of things. There are men who, 
 from the first cause, never see anything worth seeing, and others who, 
 from the second cause, always see things double or quadruple or as 
 they expect or wish to see them. 
 
 b. Want of opportunity or ability or disposition to think out the 
 
THE FORMATION OF JUDGMENTS. 105 
 
 conclusions for which one is quoted as an authority must, of course, 
 destroy the weight of the authority. In order to be an authority in 
 any department of thought a man must have had special opportunity 
 of acquaintance with that department, must have shown himself pos- 
 sessed of extraordinary ability to deal with it and of unusual mastery 
 of it, and must be disposed to seek and discern the truth in it. The 
 authorities in Law are the men who have shown themselves masters 
 of legal science. The authorities in Physical Science, are, accord- 
 ing to Professor Tait, "the advanced, best, ablest scientific thinkers." 
 The " competent authorities " in Physics are not the men who simply 
 observe and experiment, but the men of exact science, who, largely by 
 the aid of mathematics, have advanced the bounds of the science. 
 Professor Tait names as such authorities in Great Britain, " Brewster, 
 Faraday, Forbes, Graham, Rowan Hamilton, Herschel, and Talbot," 
 in the immediate past, and u Andrews, Joule, Clerk Maxwell, Balfour 
 Stewart, Stokes, William Thomson, and such like," in the present. The 
 authorities in Theology, Philosophy, etc., are the men who are masters 
 in these departments. 
 
 The utterance of a competent authority in any department has great 
 weight even when not accompanied with the reasons, because he is 
 rightly supposed to know whereof he affirms. The word of the aver- 
 age man, even if he is admitted to be familiar with his subject, has 
 just as much weight as the reasons by which he supports it, and it has 
 weight at all only as he presents his reasons along with it. He is not 
 an authority. Assertions made concerning Theology, Metaphysics, 
 etc., by experimental physicists who have given absolutely no attention 
 to those difficult departments, are worth just as much as the counter 
 assertions made concerning Experimental Physics by theologians who 
 know nothing of that department. In all such cases, however dis- 
 tinguished a man may be in his own department, his words concerning 
 the unknown department should have only so much weight as is given 
 by the reasons with which he accompanies them. 
 
 Rule 2d. — A witness or authority must be credible, i. e. t 
 must be of such a character as to be worthy of belief. 
 
 a. Whatever the opportunities or natural ability of a witness, if 
 he is shown to be careless in observing, credulous in receiving state- 
 ments, addicted to falsehood, under the influence of prejudice, or 
 swayed by motives that would warp his view of the facts, the value 
 of his testimony is just so far impaired. 
 
106 PRACTICAL LOGIC 
 
 b. The value of authority is equally affected by the credibility of 
 the one giving the opinion. If the judge who renders a certain de- 
 cision can be shown to be corrupt, or to be in any way wanting in 
 principle, his decision will come so far short of commanding assent as 
 authority. 
 
 Rule 3d. — Concurrence in testimony or authority in- 
 creases the probability of its truth. 
 
 a. The force of concurrence in testimony is broken when there is 
 evidence of collusion or pre-arrangement. Precise agreement in stat- 
 ing the general facts and all the details of any occurrence is looked 
 upon as proof of collusion ; whereas incidental variation in non-essen- 
 tial particulars, along with general agreement, shows the absence of 
 collusion and the truthfulness of the witnesses. Where there has been 
 no opportunity for collusion, concurrent testimony may become abso- 
 lutely conclusive even where all the witnesses are noted liars. In 
 such cases we cannot account for the agreement except on the ground 
 that what the witnesses independently state is true. 
 
 b. The force of concurrence in authority is subject to the same limi- 
 tations as that in testimony. Too precise agreement in statement of 
 matters of opinion indicates probable collusion. No weight is to be 
 attached to the concurrence of many judges, if it can be shown that 
 the successive decisions have all followed some one original and lead- 
 ing decision. If, however, there is evidence that each arrived at his 
 decision by independent thought, the authority may become of the 
 greatest weight, even when the word of each one separately could 
 command little or no respect. The cumulative force of convergent 
 evidence or argument is also to be considered. The convergence of 
 several lines of proof is often sufficient to render certain what perhaps 
 no one of these lines alone would fully establish. This is illustrated 
 in the proof that there is a personal God. The consent of mankind, 
 the principle of causation, the order of the universe, the intuition of 
 the infinite, the voice of conscience, and the yearnings of the affections, 
 all converge towards the common centre, a personal God, and the 
 strength of the proof lies in this convergence, rather than in the sep- 
 arate arguments taken alone. 
 
 Rule 4th. — Things absurd or impossible are not to be be- 
 lieved on the ground of testimony or authority, although 
 
THE FORMATION OF JUDGMENTS, 107 
 
 things strange, wonderful, or even miraculous may be be- 
 lieved on such ground. 
 
 Whatever is absurd or impossible, i. e., logically contradictory or 
 beyond the reach of power to accomplish, cannot, of course, be believed. 
 No testimony or authority could make one believe in a triangle with 
 four sides, or in Mill's conceived world in which two and two make 
 five. It must be observed, however, that what is merely contrary to 
 experience is not necessarily absurd or impossible. The King of Siam 
 had never in his experience known water to be transformed into a 
 solid upon which men could walk ; but every one sees that this was 
 not sufficient reason for his pronouncing the missionary, who told him 
 of such a thing, a liar and impostor, since human experience is very 
 limited. 
 
 There is need to note especially the natural inclination of men to 
 pronounce everything absurd and impossible which contradicts their 
 settled convictions, their preconceptions or their prejudices, or which 
 is repugnant to their feelings. It was once, by the majority of man- 
 kind, pronounced impossible for the earth to turn on its axis and move 
 through space with incredible rapidity without our perceiving it. It 
 was declared absolutely impossible that information should be trans- 
 mitted thousands of miles in the fraction of a second, or that a man 
 should converse with his friend hundreds of miles away. It must be 
 borne in mind that the impossible is only that w T hich is logically con- 
 tradictory or beyond the reach of power ; and that, therefore, before 
 any particular thing can be pronounced impossible, the laws and limi- 
 tations of thought and power must be comprehended and found to 
 forbid its accomplishment. A thing may, therefore, be perfectly cred- 
 ible, though it be strange, unaccountable, or even unintelligible. 
 " What is strange or unaccountable to one mind may be perfectly 
 familiar and plain to another. For the most limited intellect or ex- 
 perience to make itself the standard of the possible, would be as absurd 
 as a man's making his visible horizon the limit of space." Even tes- 
 timony to supernatural and miraculous events may be entirely worthy 
 of belief, if there be any Supernatural Power in the universe, and 
 such events may and ought to be believed if the witnesses are com- 
 petent and credible and concur in their statements. It is a remarkable 
 fact that the greatest scientists and philosophers, — such men as Bacon, 
 Locke, Descartes, Newton, Herschel, Brewster, and Faraday, — have 
 unhesitatingly believed in miracles on the ground of such testimony, 
 regarding them, not as events without any adequate cause, but as 
 
108 PRACTICAL LOGIC. 
 
 events into whose production a higher, Unseen Cause entered. In all 
 such cases, however, the witnesses to the supernatural events should 
 be subjected to the most rigid scrutiny and cross-examination, accord- 
 ing to the established rules of testimony. 
 
 It is evident that the proofs of empirical judgments never 
 give the judgments the absolutely demonstrative force which 
 belongs to the proofs of analytic and intuitive judgments, 
 but simply render them more or less probable. As the 
 entire practical ongoing of human life depends upon such 
 judgments from experience, i. e., from observation, thought, 
 testimony, and authority, the meaning and truth of Butler's 
 statement, that "probability is the guide of life," becomes 
 apparent. 
 
 Probability varies in different cases. It may in one case practically 
 amount to certainty ; in another the balance may be as a thousand, or 
 a million, or vastly more, to one, against the truth of the judgment. 
 The rational conduct of human affairs varies accordingly. Where 
 the balance of probabilities is in favor of the truth of a judgment, 
 men base their action upon it, in all the ordinary affairs of life, with 
 a confidence increasing as the degree of probability rises. When the 
 probabilities are as fifty-one to forty-nine that certain goods will 
 greatly advance in price, the enterprising merchant hesitatingly in- 
 vests in them ; as the probabilities become as seventy-five to twenty- 
 five, he invests more eagerly ; as the probabilities approach certainty, 
 he secures control of all that his capital will enable him to command. 
 Where great and permanent practical interests are involved, even 
 the lowest degree of probability should, in accordance with the dic- 
 tates of common sense, be acted upon. The man wrecked in mid- 
 ocean wisely clings to his solitary plank even when the probabilities 
 that he will be saved are only as one to a thousand or even one to a 
 million. The balancing of probabilities and deciding the course in 
 view of them is manifestly an essential part of man's rational and 
 moral discipline in this world. 
 
 Note. — Professor Jevons says of the Theory of Probabilities : " It is the very 
 guide of life, and hardly can we take a step or make a decision of any kind 
 without correctly or incorrectly making an estimate of probabilities. . . . The 
 whole cogency of inductive reasoning rests upon probabilities. The truth or 
 untruth of a natural law, when carefully investigated, resolves itself into a 
 
THE FORMATION OF JUDGMENTS. 109 
 
 high or low degree of probability, and this is the case whether or not we are 
 capable of producing precise numerical data."— Jevons' Principles of Science, 
 p. 217. 
 
 Praxis. — Examine critically the following judgments or proposi- 
 tions, — first, stating of each whether it is analytic or synthetic; 
 secondly, if analytic, developing the proof from the judgment itself; 
 thirdly, if synthetic, showing whence its proofs are to be derived and 
 bringing the proofs of the judgments from observation, testimony, and 
 authority from the proper sources : 
 
 1. Washington is the capital of the United States. 
 
 2. George Washington was a true patriot. 
 
 3. Columbus discovered America. 
 
 4. New Orleans is situated on the Mississippi. 
 
 5. England is across the Atlantic Ocean. 
 
 6. There is such a country as China. 
 
 7. Madagascar is inhabited. 
 
 8. Civilization has been progressive from the earliest ages. 
 
 9. The Aztecs reached a high degree of civilization. 
 
 10. Lying is never justifiable. 
 
 11. The Allegheny Mountains were formerly submerged. 
 
 12. The Himalayas are the highest mountains on the globe. 
 
 13. The feudal system was beneficial. 
 
 14. Honesty is the best policy. 
 
 15. Education cannot be effected by mere class-room instruction or 
 lecturing. 
 
 16. The sum of the three angles of a triangle is equal to two right 
 angles. 
 
 17. Two straight lines cannot inclose a space. 
 
 18. The earth is between 93,000,000 and 94,000,000 miles from the 
 sun. 
 
 19. Wrong-doing blinds the conscience. 
 
 20. Falsehood is dangerous. 
 
 21. The story of Christ's life and death is true. 
 
 22. Joan of Arc was a religious enthusiast. 
 
 23. In a right-angled triangle the hypothenuse is the longest side. 
 
 24. Any two sides of a triangle are together greater than the third. 
 
 25. Christianity is of divine origin. 
 
 26. The study of the classics is necessary to the highest culture. 
 
 27. North America was once inhabited by a race of Indians of 
 higher civilization than the existing tribes. 
 
 10 
 
110 PRACTICAL LOGIC. 
 
 28. Christianity is the religion which meets the needs of man. 
 
 29. A triangle cannot have more than one angle as great as a right 
 angle. 
 
 30. The moon revolves round the earth. 
 
 31. The best science recognizes a God. 
 
 32. Probability is the guide of life. 
 
 Section II.— The Products of Judgment. 
 
 The process of judging results in judgments which are 
 embodied in propositions. These products need to be care- 
 fully classified and divided, since the unfolding of judg- 
 ments depends upon a knowledge of their kinds and char- 
 acteristics, and since judgments constitute the material of 
 Reasoning, the third Form of Thought. 
 
 Judgments of content and extent and analytic and syn- 
 thetic judgments have already been considered in treating 
 the process of judgment (pp. 97-99). For further logical 
 purposes the chief divisions of judgments are based on the 
 various ways of making the predication or assertion, since 
 the assertive element is the main one in judgment. This 
 gives rise to the following divisions : 
 
 First, by the quality of the predication, whether affirmative or not, 
 into affirmative and negative judgments. This division is treated 
 under Quality of Judgments. 
 
 Second, by the extent of the predication, whether total or not, into 
 universal or total and particular or partial judgments. This division 
 is treated under Quantity of Judgments. 
 
 Third, by the directness of the predication, whether direct or indi- 
 rect, into categorical and hypothetical. Tnis division is treated under 
 Belation of Judgments. 
 
 Fourth, by the degree of certainty of the predication, whether 
 certain or not, into certain including demonstrative and assertory, and 
 not-certain including probable and possible. This division, as it has 
 reference to the results in the mind of the thinker himself, will be 
 treated, in summing up the results of thinking in its second form, at 
 the close of Part II., under Modality of Judgments. 
 
 Since the divisions of scientific syntax in Grammar depend upon the 
 forms and combinations of logical judgments or logical propositions, 
 
THE FORMATION OF JUDGMENTS. Ill 
 
 for grammatical purposes there is still another division of judgments, 
 which needs to be considered : 
 
 Fifth, by combination, whether single or not, into simple, and mul- 
 tiple or combined including complex and compound. This is treated 
 under Grammatical Combination of Judgments. 
 
 Topic First. — Quality of Judgments. 
 
 By the quality or character of the predication judgments 
 are either affirmative, as, "Belgium is populous; " or nega- 
 tive, as, " The vicious are not wise." In the former there 
 is indicated the union of the two notions by some link of 
 connection, and they are, therefore, said to agree, by the 
 principle of Identity ; in the latter there is indicated by the 
 negative the separation of the two notions, which are, there- 
 fore, said to disagree, by the principle of Contradiction. 
 
 It follows from the nature of negation that a negative copula always 
 excludes everything in the predicate, — the whole, the species, the indi- 
 viduals, — entirely from the subject. E. g., " No men are angels" cuts 
 off the entire class " angels " and all that is included in it from the 
 class "men." "Some men are not artists" cuts off the entire class 
 "artists" from these "some men." This is called the distribution of 
 the predicate, or the taking of it in its entire signification. 
 
 It should be observed that the negative particle is not always con- 
 nected with the copula, but may be placed in other parts of the propo- 
 sition ; yet in every judgment really negative it belongs only to the 
 copula. By the second Logical Postulate it is always permissible to 
 put the negative into its proper place, with the verb to be, in reducing 
 any proposition to the normal form, S is not P. "No human knowl- 
 edge is perfect " may thus be changed into, " All human knowledge 
 is not perfect." In many apparently negative propositions the force 
 of the negative particle does not fall on the copula, but upon one of the 
 terms. E. g., u Not to submit is madness " is really an affirmative prop- 
 osition, since the force of the "not" falls on the words "to submit." 
 The meaning is, "Non-submission (or resistance) is madness." Again, 
 " A person n ot vicious is virtuous" is equivalent to, "Anon-vicious 
 person is virtuous," and is, therefore, an affirmative proposition. In 
 like manner propositions apparently affirmative may be really nega- 
 tive, the force of the negative particle being in some way involved in 
 the thought, if not in the form of expression. E. g., " Only a few 
 
112 PRACTICAL LOGIC 
 
 men are wise ; " " Few men are wise ; " " But few men are wise," are 
 all substantially negative propositions, since they are equivalent to, 
 " Most men are not wise." On the other hand, " A few men are wise," 
 is an affirmative proposition. Great care should manifestly be exer- 
 cised in ascertaining the precise quality of all such propositions. 
 
 Topic Second. — Quantity of Judgments. 
 
 The quantity of judgments depends upon the extent of 
 the predication. Certain logical distinctions, which arise 
 from the combination of quantity with quality, may also 
 be most conveniently treated under this Topic. 
 
 I. Kinds of Judgments by Quantity. 
 
 The predicate notion of a judgment may be affirmed or 
 denied either of the whole q£ a subject or of a part of it 
 only. Having once formed the notion, " orange," we may 
 affirm that, "This orange is yellow," or, "Some oranges 
 are yellow," or, "All oranges are yellow." Hence judg- 
 ments by this division are universal or total and particular 
 or partial. 
 
 1. Universal or total judgments include the strictly uni- 
 versal, or those in which the notion of the subject is taken 
 in its entire extent ; the judgments in which a definite part 
 of the notion of the subject is taken; the judgments with 
 individualized, singular, or collective subjects; and equiv- 
 alent or substitutive judgments. 
 
 Universal judgments in the strict sense are those in which the pred- 
 icate notion is affirmed or denied of the entire subject notion, i. e., of 
 all that is comprehended or contained under it, whether attributes or 
 objects. The subject is, in this case, a logical whole taken in all its 
 parts. " All men are mortal ; " " Every man is mortal," are univer- 
 sal judgments, the subject embracing the total number of objects in the 
 class " man." The subject in all universal judgments, whether affirm- 
 ative or negative, is said to be distributed, because what is predicated 
 is predicated of each and every object in the entire whole. Universal 
 judgments include those in which a definite part of the subject is taken, 
 as, " These men are Japanese." They also include judgments with 
 individualized subjects, as, " This man is sober ; " and judgments with 
 
THE FORMATION OF JUDGMENTS, 113 
 
 singular subjects, as, "Bucephalus is a horse;" "France is not an 
 empire." This follows from the fact that the predicate notion is af- 
 firmed or denied of the whole subject. The same is true of judgments 
 whose subjects are collective wholes, as army, forest; mass wholes. 
 as, wheat, rice ; material wholes, as gold, stone. 
 
 From the predication of the definition, or essence, of a notion, there 
 arises a peculiar kind of universal judgment in which the subject and 
 predicate are equal and identical. This is known as the equivalent, or 
 substitutive judgment, in distinction from the simple attributive judg- 
 ment or ordinary universal. For example, " Body is extended sub- 
 stance ; " "Man is a rational unimal." In all such judgments the 
 notions or terms of both subject and predicate are taken in their entire 
 meaning, or distributed. 
 
 The signs of universal judgments are all, every, each, both, any, none, 
 neither, always, never, whoever, wherever, whatever, etc. Care must be 
 taken, however, to guard against the ambiguous use of such signs, 
 especially against such use of the word all. The word all in its proper 
 logical sense means " each and every;" but it stands sometimes for 
 "all taken together," as, "All these claims upon my time overpower 
 me." Hence may arise an ambiguity, since instead of all, in its proper 
 sense of "all taken together," we are liable, in our interpretation, to 
 put all in its logical sense of " each and every." The example could 
 not mean, " Every single claim upon my time overpowers me." 
 
 2. Particular or partial judgments embrace the ordinary 
 form including the purely indefinite and the semi-definite 
 judgments; and the more unusual forms called numerically 
 definite and plurative judgments. 
 
 Particular or partial judgments are those in which the predicate 
 notion is affirmed or denied of a number of objects less than the whole 
 denoted by the subject notion, as, "Some men are poets," " Some rulers 
 are not just." In particular judgments the naked subject must always 
 be restricted either by implication or by some restrictive term. The 
 signs of particular judgments, are, some, not all, not every, afevj, there 
 are — that, a or an, one, two, three, etc., sometimes, somewhere, etc. 
 
 The word some, as used in introducing particular judgments embod- 
 ied in propositions, is, as Hamilton has shown, ambiguous. In some 
 instances it introduces a semi-definite judgment, as, "Some men are 
 poets/'* i. e., some at most, not all. In other instances it introduces a 
 Strictly indefinite judgment, as, " Some men reason," i. e., some at 
 10* H 
 
114 PRACTICAL LOGIC 
 
 least, perhaps all. The latter is the old logical meaning of some, and 
 the judgment is wholly indefinite ; the former meaning makes the judg- 
 ment semi-definite, since it excludes all. In which sense the word is 
 used in any given instance must be determined by examining the 
 thought or, in connected discourse, the context. Numerically defi- 
 nite judgments, are those in which the predicate notion is affirmed 
 or denied of a definite number or proportion of the objects included 
 in the subject, as, " Ten men in a thousand are wise." Considering 
 the il ten men " alone as the subject, the judgment would be regarded 
 as universal, since the predicate is affirmed of all the ten. Of like 
 nature are plurative judgments which embrace more than half but 
 not all the subject. These may be numerically definite, as, " Forty 
 men out of the fifty on the steamer perished ; " or indefinite, as, " Most 
 men are not poets." In the numerically definite form the sign is found 
 in numbers expressing more than half of the whole embraced in the 
 subject. In the indefinite plurative judgment the signs are found in 
 such expressions as, more than half, the majority, many, etc. 
 
 When the predication approaches more nearly to covering the whole 
 of the subject, as in approximately universal judgments, such terms 
 are used as most, almost every one, the large majority, etc. On the 
 other hand the following signs are nearly total negatives : few, very 
 few, hardly or scarcely any, little, small, slight, rare, seldom, etc. 
 
 II. Logical Distinctions from Quantity and Quality Com- 
 bined. 
 
 Two subjects — the normal forms of judgments as they 
 appear in the syllogism, and the distribution of terms — are 
 dependent upon both Quality and Quantity, and will be 
 most naturally treated and best understood in immediate 
 connection with these topics. 
 
 1. Normal Forms of Judgment. — Men in their thinking 
 combine quality and quantity in judgments. To facilitate 
 the use of judgments in the syllogism logicians have formed 
 a complete scheme of judgments combining quality and 
 quantity, and have affixed to each form a symbol by which 
 both quality and quality are briefly expressed. The pos- 
 sible combinations are four, two of which are subdivided as 
 shown in the following form : 
 
THE FORMATION OF JUDGMENTS. 115 
 
 & g 
 bo cS 
 
 
 
 Quantity. Quality. 
 
 ' Universal Affirmative, 
 Attributive, 
 [ Substitutive, 
 Universal Negative, 
 
 ' Particular Affirmative, 
 Attributive, 
 [ Substitutive, 
 Particular Negative, 
 
 Symbol. 
 
 A, 
 U, 
 E, 
 
 I, 
 
 Y, 
 0, 
 
 These may be illustrated by examples : 
 
 All men are (some) mortals 
 [ All men are (all) rational animals 
 
 No men are (any) angels . 
 
 Some men are (some) mortals 
 [ Some men are (all) the poets 
 
 Some men are not (any) artists 
 
 Formula. 
 
 All S is (some) P. 
 All S is (all) P.] 
 No S is (any) P. 
 
 Some S is (some) P. 
 Some S is (all) P.] 
 Some S is not (any) P, 
 
 A. 
 U.] 
 E. 
 I. 
 Y.] 
 0. 
 
 The judgments in most common use are A, E, I, and 0, and the log- 
 ical processes are usually confined mainly to these. 
 
 2. Distribution of Terms. — As already indicated, a term 
 is said to be distributed when it is taken in its entire sig- 
 nification embracing each and every object included under 
 it. From the principles already presented a general state- 
 ment of the terms distributed, or taken in their full extent, 
 in the various judgments and also of those undistributed, 
 or not taken in their full extent, can readily be made. 
 These may be embodied in Rules. 
 
 Rule 1st. — All universals, — A, U, and E, — and no par- 
 ticulars, — I, Y, and 0, — distribute the subject. 
 
 Rule 2d. — All negatives, — E and 0, — and all substitutive 
 affirmatives, — U and Y, — but no attributive affirmatives, — 
 A and I, — distribute the predicate. 
 
 From the nature of quantity and quality, as seen in the statements 
 made and examples given, it appears that the six kinds of judgments 
 have their terms distributed or undistributed, as follows : 
 
116 PRACTICAL LOGIC 
 
 A distributes the subject only. 
 
 U " both subject and predicate. 
 
 E " both subject and predicate. 
 
 I " neither subject nor predicate. 
 
 Y " the predicate only. 
 
 " the predicate only. 
 
 Praxis. — State of each of the following judgments, — first, to which 
 of the six forms it belongs, and whether its terms are distributed or 
 undistributed and why, marking the judgment by its appropriate 
 letter; secondly, if the judgment is particular, whether it is definite, 
 semi-definite, numerically definite, plurative, etc., and if universal, 
 whether singular, attributive, substitutive, etc.; and, thirdly, if am- 
 biguous, wherein the ambiguity consists : 
 
 1. All oaks are trees. 2. Some men have genius. 3. Poets are men 
 of genius. 4. Body is extended substance. 5. This inkstand is made 
 of glass. 6. The senate has adjourned. 7. Birds breathe and fly. 8. 
 11 All Jerusalem went out to meet him." 9. Salt is chloride of sodium. 
 10. Some men reason. 11. Some men seek reputation. 12. A few were 
 saved. 13. He that does not heed, stumbles. 14. Nine boys out of ten 
 prefer play to study. 15. Forty of the fifty sailors perished. 16. Not 
 every mistake is culpable. 17. Milton was blind. 18. All men are 
 not liars. 19. God is good. 20. Gold is a heavy metal. 21. With rare 
 exceptions men are selfish. 
 
 Topic Third. — Relation of Judgments. 
 
 The relation of judgments depends upon the manner of 
 predication. The predication may be made either simply 
 and positively or may be made to depend upon something 
 else. The first gives rise to the categorical judgment ; the 
 second to the hypothetical. 
 
 Note.— The ordinary grammatical division of propositions as embodied in 
 sentences is based upon the mental states embodied. It embraces the follow- 
 ing kinds of sentences: 
 
 /Expressing Cognition or Intellect, including, — 
 
 I r Interrogative, showing search for ground of judgment, 
 w \ < Hypothetical, showing certain grounds only as still in doubt, 
 a ) I Categorical, showing the comparison and connection completed ; 
 o /Expressing Emotion or Sensibility, — 
 g J Exclamatory, embodying feeling ; 
 «0 /Expressing Conation or Will, including, — 
 
 I f Optative, indicating wish or choice, 
 
 \ 1 Imperative, indicating determination or volition. 
 
THE FORMATION OF JUDGMENTS. 117 
 
 Interrogative sentences may have the same terms as the other sentences ex» 
 pressing cognition, and are treated in Logic in the same manner as those sen- 
 tences. The elements of emotion and will do not enter into the thought of the 
 proposition, in the strict sense. In so far as the sentences based upon them ex- 
 press thought in the proper sense, they may be treated as propositions express- 
 ing cognitions^ and so become either categorical or hypothetical. Bee Davis' 
 Logic, p. 82. 
 
 1. A categorical judgment is one in which the predicate 
 is affirmed or denied of the subject simply and absolutely 
 or without condition, as, " Captain Jack was a Modoc chief; " 
 " Benedict Arnold was not a patriot." The affirmatives 
 are based on the principle of Identity, the negatives on 
 that of Contradiction. 
 
 2. A hypothetical judgment is one in which the predica- 
 tion is based upon some circumstance " which must be 
 granted or supposed before the assertion becomes applicable." 
 The supposition may be either a condition or an alternative 
 or both these combined ; and hypothetical judgments are, 
 therefore, of three kinds, conditional, disjunctive, and di- 
 lemmatic. 
 
 (1.) A conditional or conjunctive judgment suspends the predication 
 upon some supposed circumstance (called a condition), as, " If the sun 
 
 shines the snow melts." This may be put into the form, M The snow 
 is, — if the sun shines, — melting." " Melting " is predicated of " snow " 
 upon the condition that " the sun shines." If it be true that " the 
 sun shines," then it is true that " the snow melts." The supposed cir- 
 cumstance, "If the sun shines," is called the antecedent; the judg- 
 ment suspended upon the condition is called the consequent. The rela- 
 tion between the two is that of reason. and consequent, or cause and 
 effect. The conditional judgment is, therefore, based upon the princi- 
 ple of Sufficient Reason. The signs of conditionals are, if, when, in 
 case of, etc. 
 
 Conditional judgments may be converted into categorical form by 
 changing the signs, if, when, in case of, etc., into such phrases as "the 
 case of," "the circumstances in which," etc. Thus the conditional, 
 " If the sun shines the snow melts," becomes "The case of the sun's 
 shining is the case of the snow's melting." 
 
 (2.) A disjunctive judgment suspends the predication upon some 
 alternative introduced by "either — or." It involves two or more 
 
118 PRACTICAL LOGIC. 
 
 judgments, all of which cannot be true, but one or more of which, by 
 the principle of Excluded Middle, must be true. Thus in the disjunc- 
 tive, " Either the Bible is false or holiness ought to be followed," there 
 are two alternative judgments, " The Bible is false ; " and M Holiness 
 ought to be followed." " Either London is in England or it is not," 
 contains two alternative judgments, " London is in England;" u Lon- 
 don is not in England." One or other of them must be true; the 
 other cannot be. The disjunctive needs to be carefully distinguished 
 from the partitive judgment, which, under the form of a disjunctive, 
 simply predicates of a genus its several species ; as, " All Africans are 
 either bond or free." The genus, Africans, is in this case made up of 
 the component species, bond and free, which are affirmed of it not 
 alternatively nor disjunctively, but concurrently. The affirmation of 
 the one is not a denial of the other. 
 
 Disjunctive judgments may be converted into categorical form by 
 using all their members for one of the terms, and the phrase " possible 
 cases," or, " the only alternative," or one like it, for the other term. 
 The disjunctive, " This season is either Spring, Summer, Autumn, or 
 Winter," becomes, " All the possible cases regarding this season are 
 Spring, Summer, Autumn, and Winter." Disjunctives may also be 
 converted into conditionals by taking the contradictory of one of the 
 members for the antecedent and making the other members conse- 
 quents. Thus, "If it is not Summer, it is either Autumn, Winter, or 
 Spring." 
 
 (3.) A dilemmatic judgment is a hypothetical involving a combina- 
 tion of the conditional and the disjunctive. The disjunctive may fall 
 either in the antecedent or in the consequent. Thus, " If a man falls 
 into the sea, he will either sink or swim ; " "If man is either praise- 
 worthy or blameworthy, he must be a free agent." 
 
 A dilemmatic judgment may be converted into categorical form by 
 changing each of its elements, according to the principles laid down 
 under hypo the ticals and disjunctives. 
 
 Topic Fourth. — Grammatical Combination of Judgments 
 or Propositions. 
 
 Judgments embodied in propositions are either single or combined. 
 Combined judgments are combined by subordination or by co-ordina- 
 tion. Propositions are, therefore, simple, complex, or compound. 
 
 A simple proposition consists of only one subject and predicate. Both the 
 subject and predicate may, however, be grammatically very complex, e. g., "A 
 
THE FORMATION OF JUDGMENTS. 119 
 
 legitimate and forcible argument may fail to win the assent of a prejudiced 
 man." The kinds of judgments thus far treated are chiefly forms of simple 
 judgments embodied in simple propositions. 
 
 A complex proposition consists of a principal judgment with one or more 
 subordinate judgments, e. g., u Man who is born of a woman is of few days." 
 The subordinate elements appear as substantive, adjective, or adverbial elements, 
 so that in logic the complex sentence is treated as embodying a simple judg- 
 ment. The office of the subordinate clauses is explicative, as, " Whoever is 
 right, is safe; " or restrictive, as, " Men who are avaricious are discontented." 
 
 A compound proposition is made up of two or more co-ordinate judgments, as. 
 " Art is long, and time is fleeting." For logical purposes the constituent judg- 
 ments of a compound proposition require separate and independent statement. 
 Co-ordination is either copulative, adversative, disjunctive, or causal. The co- 
 ordination is copulative when two or more thoughts, which are considered 
 independent, are so united together that the thought expressed in the co-ordi- 
 nated judgment gives a greater extent to the thought of the preceding judg- 
 ments, e. g., "Socrates and Plato were wise;" "Plato was a philosopher and 
 Sophocles was a poet." The copulative connection may be either annexive, en- 
 hansive, intensive, or ordinative. The co-ordination is adversative when the 
 judgments united in thought stand in opposition to one another, e. g., "Not 
 the rich are happy, but the good." The opposition may be contradictory, con- 
 trary, or restrictive. The co-ordination is disjunctive when the judgments 
 united in the one thought exclude one another, e. g. " He is either here or he 
 is not here." The disjunction is either exclusive as in the ordinary disjunctive 
 judgments, or sepamtive as in comparisons. The co-ordination is causal when 
 the last of the co-ordinate judgments denotes the ground of the preceding judg- 
 ment, or the conclusion from it, as, " Aristotle was an accurate thinker, for he 
 formed conceptions and judgments well." The causal relation in the wide 
 sense, may be either reason, or cause proper, or conclusion from reason, or conse- 
 quence from cause. 
 
 Note.— For a full presentation of the principles of subordination and co-or- 
 dination, see Runner's Latin and Greek Grammars, and Becker's German 
 Grammar. 
 
 Praxis. — Examine and characterize the following judgments, — First, 
 reducing them to the normal form ; secondly, bringing out the connect- 
 ing links; thirdly, indicating the sources of proof; fourthly, giving 
 the quantity, quality, and relation, and showing the distribution of 
 the terms ; fifthly, stating whether simple or combined, and if com- 
 bined showing whether complex or compound, and bringing out the 
 particular relations of subordination or co-ordination : 
 
 1. No reptiles have feathers, 
 
 2. Grace is unmerited favor. 
 
 3. None are free who do not govern themselves. 
 
 4. He that ruleth his own spirit is greater than he that taketh a 
 city. 
 
 5. George Eliot was the wife of George H. Lewes\ 
 
120 PRACTICAL LOGIC 
 
 6. He that getteth silver is not satisfied with silver. 
 
 7. Thomas Jefferson prepared the first Anglo-Saxon Grammar pro- 
 duced in America. 
 
 8. There is no fireside, howsoe'er defended, 
 But has one vacant chair. 
 
 9. Never morning wore to evening but some heart did break. 
 
 10. The rich are not necessarily happy, for happiness is not the 
 result of external circumstances. 
 
 11. Those here present constitute the class in Logic. 
 
 12. All that glitters is not gold. 
 
 13. Man was originally a long-eared animal of arboreal habits. 
 
 14. A miracle is impossible. 
 
 15. No such thing as a miracle has ever been experienced. 
 
 16. Who steals my purse, steals trash. 
 
 17. Life every man holds dear. 
 
 18. If Christ rose from the dead, then Christianity is true. 
 
 19. Either Richard III. was a monster or Shakespeare was wrong.' 
 
 20. If Socrates was innocent, Anytus was either deceived or per- 
 jured. 
 
 21. Wherever there is smoke, there is fire. 
 
 22. If Caesar lives, he will rule or ruin. 
 
 23. He would have gone, but was prevented by sickness. 
 
 24. Goliath uttered his challenge and David accepted it. 
 
 25. First, the dawn ; then, the rising sun ; and last, the busy tide 
 of life. 
 
 26. There are studies much vaunted, yet of little utility. 
 
 27. Some democracies are unstable. 
 
 28. Some honest men become bankrupt. 
 
 29. The world's no neuter ; it will wound or save. 
 
 30. The country is generally flat or but slightly undulating. 
 
 31. Wealth may seek us ; but wisdom must be sought. 
 
 32. He had the air of dignity, yet of deep feeling. 
 
 33. For man to tell how human life began is hard ; for who him- 
 self beginning knew ? 
 
 34. Thy father slew my father ; therefore die. 
 
 35. We have no slaves at home — then why abroad ? 
 
 36. He is very great in knowledge, and accordingly valiant. 
 
 37. I have the wish, but want the will to act. 
 
 38. The widow and her child returned to England, and lived almost 
 hopeless in their old home. 
 
THE UNFOLDING OF JUDGMENTS. 121 
 
 CHAPTER II. 
 
 THE UNFOLDING OF JUDGMENTS, 
 
 The best use of judgment in the practical work of think- 
 ing requires that the thinker should be able to unfold what 
 may be contained in any judgment, or implied in it, or im- 
 mediately inferred from it. Hence the following Topics : 
 
 First, the development of contained judgments. 
 Second, the development of implied judgments. 
 Third, the development of inferred judgments, 
 
 Note.— Some logicians consider this subject as a part of Reasoning. Ac- 
 cording to these, Reasoning is, either by inference from one judgment to an- 
 other derived from it ; or from two judgments to a third, which could not be 
 derived from either alone but is drawn from both combined. The latter is 
 called Mediate Inference ; the former Immediate Inference. The subjects of 
 the present Chapter are, according to this view, treated under the head of Rea- 
 soning. They are, however, properly to be treated under Judgment, for they 
 all flow from the nature of conceptions as already presented and from the re- 
 lations of these conceptions in judgments and propositions. 
 
 Section I.— Development of Contained Judgments. 
 That which is contained in any judgment may be brought 
 out by analysis of the content or extent of its terms, the 
 subject and predicate. 
 
 This form of analysis is of great service in careful thinking and 
 especially in confirmation of judgments. It is applicable, of course, 
 only to judgments in which at least one of the terms is complex or 
 has component attributes or species. The process must conform to the 
 laws of Partition and Division. 
 
 The proposition, " The highest civilization is dependent on Chris- 
 tianity," may be analyzed, as a proposition of content, either by par- 
 tition of the subject or of the predicate. The subject, " the highest 
 civilization," includes as marks or attributes : the most righteous civil 
 government; the completest development of the arts industrial and 
 aesthetic ; the broadest and most liberal education ; the best manners 
 and morals, or conduct in all relations ; the highest spirit of enter- 
 prise and progress. The proposition may therefore be unfolded into 
 the following : The most righteous civil government is dependent on 
 11 
 
122 PRACTICAL LOGIC. 
 
 Christianity ; The completest development of the arts industrial and 
 sesthetic is dependent on Christianity ; The broadest and most liberal 
 education is dependent on Christianity ; The best form of manners and 
 morals, or conduct, in all relations is dependent on Christianity ; The 
 highest degree of enterprise and progress is dependent on Christianity. 
 The predicate element, " Christianity," may be analyzed to meet the 
 requirements of these propositions for proof. From this point of view, 
 it includes the following marks : the perfect standard of justice ; the 
 true theory of activity and beauty ; the grandest system of truth ; 
 the complete theory of responsibility and duty ; the inspiring prin- 
 ciples of progress. The proposition may, therefore, be unfolded into the 
 following : The highest civilization is dependent upon Christianity as 
 a perfect standard of justice ; The highest civilization is dependent 
 upon Christianity as the true theory of activity and beauty ; The 
 highest civilization is dependent on Christianity as embracing the 
 grandest system of truth ; The highest civilization is dependent on 
 Christianity as the complete theory of responsibility and duty ; The 
 highest civilization is dependent on Christianity as containing the in- 
 spiring principles of progress. 
 
 Propositions of extent may be unfolded by the principles of division. 
 Thus, " Free institutions are conducive to progress,'' may be unfolded 
 through the subject as a genus, as including free governmental institu- 
 tions v free educational institutions, free social institutions, free religious 
 institutions, etc. ; and through the predicate, as including political prog- 
 ress, educational progress, social progress, religious progress, etc. 
 
 To the development of contained judgments manifestly belongs also 
 what Thomson names, " Immediate Inference by the Sum of several 
 Predicates." " Copper is a metal, red, malleable, ductile, etc.," is in 
 no proper sense an immediate inference from the judgments, " Copper 
 is a metal," " Copper is red, etc.," but a simple compounding of them. 
 So these component judgments are simple constituents of the general 
 judgment, and may be unfolded from it. 
 
 Praxis. — Develop the following propositions by Subject and Pred- 
 icate, and suggest the sources of proof for the resulting propositions: 
 
 1. The studies of the High School Course are best- fitted to prepare 
 for the pursuits of business life. 
 
 2. The studies of the College Course are best fitted to prepare for 
 the work of the professions. 
 
 3. The Fine Arts are favorable to a pure morality. 
 
THE UNFOLDING OF JUDGMENTS. 123 
 
 4. The study of the Ancient Classics is the best discipline for the mind. 
 
 5. Manly qualities are becoming to a student. 
 
 6. Proper protection of the various industries is essential to national 
 prosperity. 
 
 7. The discipline of life is essential to man's development. 
 
 8. Division of labor is essential to national wealth. 
 
 Section II.— Development of Implied Judgments. 
 The implied judgment, according to Davis, " is one that 
 actually exists together with the given judgment, either 
 merely in thought or involved covertly in the expression." 
 Several simpler and less important forms of implication 
 need to be noted, but especially the more important form 
 named obversion. 
 
 Topic First. — Simpler Forms of Implication. 
 
 These are chiefly forms of interpretation of the language 
 or thought. 
 
 Such judgments may be covertly implied in the language. Thuc, 
 in the proposition, " Few men are wise," it is covertly implied by the 
 language that " Most men are not wise." "Some men are rich," im- 
 plies that " Some men are not rich." Such judgments are sometimes 
 implied in the thought. Thomson places under immediate inference, 
 what he names, " Immediate Inferences of Interpretation." It is not 
 strictly inference but rather implication. Thus, in the judgment, "John 
 loves Mary," it is implied that " John lives," that, "Mary lives," and 
 that, " there is such a thing as love." 
 
 The development of active and passive forms of judgments from 
 each other may also be placed here. In the active form, "ISapoleon 
 conquered Europe," is implied the passive form, " Europe was con- 
 quered by ISapoleon. " 
 
 In any simple proposition many other propositions may be implied. 
 Thus, "Yesterday I lifted one hundred pounds," implies judgments 
 of the existence of yesterday, of the one hundred pounds, of myself, of 
 the lifting, of memory, of time, of personal identity, of will power, etc. 
 
 Topic Second. — Obversion. 
 
 Under implied judgments belongs also what Bain calls 
 obversion. It is sometimes termed, " Immediate Inference 
 
124 PRACTICAL LOGIC. 
 
 by Reciprocal Change of Positive and Privative Concep- 
 tions.'* In affirming one thing we impliedly deny the op- 
 posite. Obversion is the bringing out and denying of this 
 opposite or reverse form. 
 
 Thus, " The road is level ; " " The road is not inclined ; " are not 
 two facts, but the same fact from different sides. The second is not an 
 inference from the first, but something implied in the first, — an obverse 
 form of the first. "Whoever is wise is not foolish; " we must grant 
 the obverse form if we grant the positive. In obversion the negative 
 form may be taken either as infinitated or as simply privative. " Wise " 
 implies the infinitated notion, "not-wise" or " non-wise," the two to- 
 gether making up the universe of being ; and also the privative, " not- 
 wise " or " unwise." 
 
 Each of the normal forms of judgment, — A, E, I, 0, — 
 has its obverse form. For developing these obverse implied 
 judgments we have the following 
 
 Rule. — Obvert the predicate (i. e. } change it to the infin- 
 itated or privative form) and then change the quality of the 
 judgment. 
 
 Note.— To avoid awkward compounds with non and not, in obverting and 
 changing the quality of judgments, various prefixes and suffixes are often used, 
 as, in-, un-, dis-, less-, etc. ; and uncompounded negatives, as unwise and foolish, 
 instead of not- wise. Great care needs, however, to be taken, as these terms 
 are often not privatives, but only signify the existence of the quality in a low 
 degree. 
 
 Taking the four principal judgments as embodied in 
 propositions, in the order of the letters representing them, 
 and applying the Rule given above, we get the obverse 
 forms : 
 
 1. The normal form of the universal affirmative, A, is as follows: 
 
 Every x is y ; Every man is mortal. 
 Obverting the predicate, this becomes : 
 
 Every x is not-y ; Every man is (not-mortal) immortal. 
 Changing the quality of the judgment from affirmative to negative, 
 it becomes : 
 
 No x is not-y ; No man is (not-mortal) immortal. 
 
THE UNFOLDING OF JUDGMENTS, 125 
 
 2. The normal form of the universal negative, E, is as follows : No 
 x is y ; No men are angels. 
 
 Obverting the predicate, this becomes : 
 
 No x is not-y ; No men are not-angels. 
 Changing the quality of the judgment from negative to affirmative, 
 it becomes : 
 
 Every x is not-y ; All men are not-angels (excluded from angels). 
 
 3. The normal form of the particular affirmative, I, is as follows : 
 Some x is y ;' Some men are wise. 
 
 Obverting the predicate, this becomes : 
 
 Some x is not-y ; Some men are (not- wise) foolish. 
 
 Changing the quality of the judgment from affirmative to negative, it 
 
 becomes : 
 
 Some x is not not-y ; Some men are not foolish. 
 
 4. The normal form of the particular negative, 0, is as follows: 
 Some x is not-y ; Some men are not wise. 
 
 Obverting the predicate, this becomes : 
 
 Some x is not not-y ; Some men are not (not-wise) unwise. 
 Changing the quality of the judgment from negative to affirmative, it 
 becomes : 
 
 Some x is hot-y ; Some men are (not- wise) unwise. 
 
 Praxis. — State what is implied in the following propositions by the 
 various forms of implication just explained : 
 
 1. Napoleon was an ambitious conqueror. 2. The diligent student 
 will become wise. 3. Wellington was the soldier of duty. 4. John 
 Howard was philanthropic. 5. Greece is a name of glory. 6. War 
 is productive of evil. 7. The peacemakers are blessed. 8. Cold kills 
 animals. 
 
 Section III.— Development of Inferred Judgments. 
 
 An inferred judgment, according to Davis, is " one that 
 only virtually or potentially exists in the given judgment, 
 and is derived from it." Its statement contains " something 
 new, there is a step forward, a progress of thought. In the 
 inferred judgment there is always either a different subject, 
 or a different predicate, from that of the premise, and per- 
 haps both." 
 
 The so-called inferred judgments may be reached from 
 11* 
 
126 PRACTICAL LOGIC. 
 
 other judgments either by Addition, Disjunction, Conver- 
 sion, or Opposition. Of these forms the last two are the 
 most important. 
 
 Topic First. — Inferred Judgments by Additions. 
 
 Determinants may be added to both terms of a judgment which is 
 thereby rendered more definite, e. g., "A negro is a fellow-creature; 
 therefore, a suffering negro is a suffering fellow-creature.'* The orig- 
 inal terms of the judgment may themselves be made determinants or 
 marks of new conceptions introduced into the judgment, e. g., " Oxy- 
 gen is an element ; therefore, the decomposition of oxygen is the de- 
 composition of an element." On the same principles two judgments 
 may be amalgamated ; as, " Honesty deserves reward, and a negro is 
 a fellow-creature ; therefore, a negro who shows honesty is a fellow- 
 creature deserving of reward." Care must be taken in all these forms 
 of addition to keep the distribution of the terms unchanged. 
 
 Topic Second. — Inferred Judgments by Disjunction. 
 
 Since the members of a disjunctive judgment are mutually exclusive, 
 we may infer from the disjunctive, " The teeth are either incisor, 
 canine, bicuspid, or molar teeth," the judgment, " The molar teeth are 
 neither incisor, canine, nor bicuspid." As the dividing members in a 
 disjunctive judgment exhaust the whole subject divided, we may infer 
 that the part of the whole not contained in one member must be in 
 some other. Hence from the judgment just given come such inferred 
 judgments as, "All teeth which are not molar are either canine, inci- 
 sor, or bicuspid teeth." 
 
 Topic Third. — Inferred Judgments by Conversion. 
 
 Illative Conversion of judgments is such a transposition 
 of the subject and predicate of a judgment that the con- 
 verse or transposed form is a legitimate inference from the 
 convertend or original judgment. Three general Rules must 
 be observed in conversion : 
 
 Rule 1st. Before conversion reduce the proposition to the 
 strict logical form, in which subject, copula, and predicate 
 distinctly appear. 
 
 Rule 2d. No term not distributed in the convertend must 
 be distributed in the converse. We may infer from all to 
 
TEE UNFOLDING OF JUDGMENTS. 127 
 
 all, from all to some, and from some to some, but not from 
 some to all. 
 
 Rule 3d. The transfer of the terms should be total. In 
 other words, the whole naked subject (i. e., the subject 
 without its sign of quantity, every, all, some, etc.) must be 
 transferred to the predicate, and the whole naked predicate 
 must be transferred to the subject. 
 
 Confining attention mainly to the four attributive judgments, A, E, 
 I, 0, — since these are all the forms of which any special nse is ordina- 
 rily made in compendiums of Logic, — it will be seen that there are 
 three principal forms of conversion. 
 
 First, Simple Conversion when neither the quantity nor the quality 
 is changed ; 
 
 Second, Conversion by Limitation when the quantity is changed. 
 
 Third, Conversion by Negation or Contraposition, when the qual- 
 ity is changed. 
 
 1. Simple Conversion is where the terms can be trans- 
 posed without change of either quantity or quality. This 
 can, of course, occur only when both subject and predicate 
 are distributed, as in E, and where both are undistributed, 
 as in I. 
 
 (1.) Let E, " No one without a love of beauty can be an eminent 
 artist," be given for conversion. The Rules should be applied in order. 
 By Rule 1st, the proposition becomes, " Every one without a love of 
 beauty is not any one who can be an eminent artist." By Rule 2d 
 and Rule 3d, the converse becomes, " Any one who can be an eminent 
 artist is not any one without a love of beauty." The converse is 
 still E. 
 
 (2.) Let I, " Some good men are bad poets," be given. The propo- 
 sition is already in strict logical form. By Rules 2d and 3d the con- 
 verse becomes, "Some bad poets are good men." The converse is 
 still I. 
 
 (3.) Substitutive and equivalent judgments, XT and Y, are, of course, 
 converted by simple transposition of the terms. " All bodies are ex- 
 tended substances " becomes, " All extended substances are bodies." 
 
 2. Conversion by limitation (per accidens) takes place 
 
128 PRACTICAL LOGIC. 
 
 where it i^ necessary, in order to an illative transposition, 
 that the quantity of the proposition should be changed 
 from universal to particular, while the quality remains 
 unchanged. This will, of course, occur where the subject 
 is distributed and the predicate undistributed, i. e., in A. 
 As some may be inferred from all, E may also be converted 
 by limitation. 
 
 (1.) Let A, "All poets are men," be given for conversion. It is 
 already in strict logical form. In order to conform to Rule 2d, the 
 predicate must be limited to " some men." By Rule 3d the converse 
 becomes, "Some men are poets;" or, "Some men are all the poets." 
 The converse of A is L 
 
 (2.) Let E, "No men are perfect," be given for conversion by limi- 
 tation. Completing the form, limiting the quantity of the predicate, 
 and then making a total transfer of the terms, the converse becomes, 
 " Some perfect things are not men." The converse is 0. By simple 
 conversion it would be E. 
 
 3. Conversion by Negation or Contraposition takes place 
 where it is necessary in order to illative transposition, that 
 the quality of the judgment should be changed, while the 
 quantity remains unchanged. This occurs in 0. 
 
 Let 0, " Some quadrupeds are not horses," be given for conversion. 
 If converted simply, it would be, " Some horses are not quadrupeds," 
 which is absurd. This result is avoided by obverting, or infinitating 
 the proposition, and then converting simply. Infinitating the predicate, 
 the proposition becomes, "Some quadrupeds are (things) not-horses;" 
 and by conversion, "Some things not-horses are quadrupeds." Thus 
 the converse of is I. 
 
 Topic Fourth. — Inferred Judgments by Opposition. 
 
 Opposition is the name given to the differences in quan- 
 tity or quality, or both, between judgments having the 
 same naked subject and predicate. Legitimate inferences 
 follow from opposition. 
 
 Between the judgments, A, E, I, 0, to which attention is 
 here chiefly confined, there are five kinds of opposition, 
 
THE UNFOLDING OF JUDGMENTS. 
 
 129 
 
 which are exhibited by the following diagram, called the 
 Square of Opposition, 
 
 All men are true, 
 (Subaltemans) 
 
 A Contrary.. 
 
 E No men are true. 
 (Subaltemans) 
 
 % 
 
 .&' 
 
 \& 
 
 c3 
 
 «*■ 
 
 *?% 
 
 <> 
 
 c3 
 
 Some men are true, • .-'" ""• j Some men are not true. 
 (Subalternate) I Subcontrary (Subalternate) 
 
 1. Contradictory Opposition, which is the only perfect 
 form, exists between the propositions A and 0, E and I, 
 
 which differ both in quantity and quality. By the principles 
 of Contradiction and of Excluded Middle, of two contra- 
 dictory propositions both cannot be true and both cannot 
 be false. 
 
 Rule. — From the truth of either of two contradictions 
 the falsity of the opposite follows ; and from the falsity of 
 either the truth of the opposite follows. 
 
 If A, "All men are true," be sublated (denied) then we can posit 
 (affirm) 0, "Some men are not true." If it be not true that "All 
 men are true," then it is certain that, (at least) "Some men are 
 not true." If 0, " Some men are not true," be denied, then A, " All 
 men are true," may be affirmed ; but if the former be affirmed, the 
 latter may be denied. 
 
 Contradictory opposition is of special service in indirect proof. 
 Instead of showing an opponent's arguments false and his position, 
 therefore, unsustained, it is often better to prove the truth of the con- 
 tradictory and then infer the falsity of his position. E. g., if one 
 affirms that "All scientists are extreme evolutionists," which is A, 
 the best way to meet it is by establishing the contradictory 0, " Some 
 scientists are not extreme evolutionists ; " or, " Some one scientist, as 
 Prof. Tait, is not an extreme evolutionist." If this be established the 
 necessary inference is that A is false. The form of indirect proof 
 known as reductio ad absurdum, largely used in geometrical demon- 
 strations, instead of demonstrating a proposition directly, demonstrates 
 
 I 
 
130 PRACTICAL LOGIC. 
 
 that its contradictory is absurd, and thence immediately infers the 
 truth of the proposition. 
 
 2. Contrary Opposition is between the universal proposi- 
 tions A and E, which differ in quality only. 
 
 Rule. — From the truth of a judgment the falsity of its 
 contrary opposite follows ; from its falsity nothing follows. 
 
 Both A and E cannot be true. From the truth of A the falsity of 
 E follows, and vice versa. E. g M if A, " All men have conscience," be 
 true, then E, " No man has a conscience," is false ; and if the latter be 
 true then the former is false. From the falsity of one contrary nothing 
 follows with regard to the other. If it be false that, " All men are 
 poets," it does not follow that, " No men are poets." But both may 
 be false. E. g., the propositions, A, "All men are poets," and E, "No 
 men are poets," are both false, since the truth lies between the two 
 and is expressed in I, " Some men are poets." In individual proposi- 
 tions, as, " Shakespeare was a poet," the opposition appears as the sim- 
 ple negative, " Shakespeare was not a poet." - 
 
 3. Subcontrary Opposition is between the particular prop- 
 ositions I and 0, which differ in quality only. 
 
 Rule. — If one sub-contrary be true, nothing follows in 
 regard to the other; but if one be false, then the other must 
 be true. 
 
 For example, if I, "Some wars are evil," be true, it does not follow 
 from this that 0, " Some wars are not evil," is true. But if I, " Some 
 wars are evil," be false, then " Some wars are not evil," must be true. 
 
 4. Subalternate Opposition is between the propositions 
 A and I, E and 0, differing in quantity only. 
 
 Rule. — If the universal, A or E, be true, the particular 
 I or 0, must be true ; and if the particular I or 0, be false, 
 then the universal, A or 0, must be false. 
 
 If A, "All men are liars," is true, then I, "Some men are liars," is 
 also manifestly true. If I, "Some men are perfect," is false, then A, 
 " All men are perfect," is false. 
 
 The results may be summed up as follows : 
 
TJJF UNFOLDING OF JUDGMENTS. 131 
 
 Contradictories. Contraries. Subalterns. 
 
 ,2 f If A is true, is false, ....E false, I true. 
 
 | J If E " , I " ,....A " , " . 
 
 > j If A is false,. ...O is true, E undetermined,... I undetermined. 
 
 5 I If E " , I '.« , A " ,...0 
 
 Contradictories. Subcontraries. Subalterns. 
 
 2 C If I is true, E is false,. ...0 undetermined,. ..A undetermined. 
 
 g J If " , A '- ,....1 M ,...E 
 
 '■g j If I is false, E is true,....0 true, A false. 
 
 £ (if " , A " I '• , E •' . 
 
 Praxis. — Apply exhaustively the principles of implication and also 
 the principles of immediate inference in its four kinds, to the follow- 
 ing judgments, giving the quantity and quality of the judgments : 
 
 1. All the righteous are happy. 2. No human virtues are perfect. 
 3. Some possible cases are probable. 4. The just are (all) the holy. 
 5. Some men are all the poets. 6. All the insincere are dishonest. 
 7. No unjust act is unpunished. 8. Some unfair acts are unknown. 
 9. The unlawful is the (only) inexpedient. 10. No brutes are re- 
 sponsible. 11. Heaven from all creatures hides the book of fate. 12. 
 Fair promises are not often to be trusted. 
 
 SUMMARY OF RESULTS. 
 
 The aim of the Logic of Judgment is to train to the 
 best thinking and fullest appreciation of thought in the 
 second form. The perfection of thinking in judgment de- 
 pends upon the certainty of the connection of the subject 
 and predicate. This gives rise to what is called the Modal- 
 ity of Judgments. 
 
 1. By the degree of certainty of the predication to the 
 mind of the thinker or others, all judgments have been 
 divided into Demonstrative, Assertory, and Problematic. 
 
 (1.) A demonstrative or apodictic judgment is one that is certain to 
 him who holds it, and that may be made certain to all sane minds suf- 
 
132 PRACTICAL LOGIC. 
 
 ficiently intelligent to understand the signification of the judgment 
 itself and its evidence. All analytic judgments are demonstrative, or 
 are certain to him who holds them, and may be made certain to all 
 other sane minds of sufficient intelligence to understand the signifi- 
 cance of the terms. All intuitive judgments are also demonstrative, or 
 have both subjective and objective certainty. These include the truths 
 of Mathematics, the fundamental principles of Logic, the axioms of 
 Ethics and Metaphysics. All judgments reached by immediate infer- 
 ence from these are also demonstratively certain. 
 
 (2.) An assertory judgment is one that announces what is known 
 as actual. It is certain only to hirn who holds it, but not capable of 
 being made certain to others of different moral disposition. " It com- 
 mends itself to our moral nature, and in so far as other men are of the 
 same disposition, they will accept it likewise." This holds especially 
 of higher moral and religious truths. Moral and religious deterio- 
 ration prevents their acceptance. 
 
 (3.) " A problematic judgment is one that is neither held with entire 
 certainty by the thinking subject, nor can we show that it truly rep- 
 resents the object about which we judge. It is a mere opinion.' 1 
 Problematic judgments constitute one of the necessary stages in the 
 progress towards truth. " Great discoveries are problems at first . . . 
 Whenever we judge about variable things, as the future actions of 
 men, the best course of conduct for ourselves under doubtful circum- 
 stances, historical facts about which there is conflicting testimony, we 
 can but form a problematical judgment, and must admit the possibility 
 of error at the moment of making our decision." 
 
 2. A simpler division of judgments, by the degree of cer- 
 tainty in the mind of the thinker, is into Certain, Probable, 
 and Doubtful. 
 
 (1.) A certain judgment is one in which the knowledge that the 
 connection between the subject and predicate corresponds to the reality 
 is absolute and unquestionable. All analytic judgments, all intuitive 
 judgments, all immediate inferences from certain judgments, all strict 
 deductions from certain or necessary premises may become certain to 
 the thinker. 
 
 (2.) A probable judgment is one in which the knowledge that the 
 connection between the subject and predicate corresponds with the re- 
 ality is not absolute and unquestionable. The boundary line between 
 the probable and doubtful is not always clearly marked, since, in com- 
 
THE UNFOXDING OF JUDGMENTS. 133 
 
 mon language, the degrees of probability may reach all the way from 
 the nearest approach to certainty that a judgment is true, down to 
 the nearest approach to certainty that it is not true, i. e., from the 
 nearest possible to absolute certainty, to the nearest possible to abso- 
 lute uncertainty ; while the degrees of doubtfulness may have the 
 same wide scope. It may be said, however, in general, that a strictly 
 probable judgment is one which has the balance of proof in its favor, 
 and that a doubtful judgment is one which has the balance of proof 
 against it. As has already been seen, man receives most of the knowl- 
 edge used in the conduct of life, in such a way that it is not certain, 
 but at best only more or less probable. All the acquired perceptions 
 of the senses and consciousness are mixed with inferences, and, there- 
 fore, only probable ; while only the original or intuitive perceptions 
 are certain. The conclusions of finite reason, especially by the induc- 
 tive processes, are liable to error, and, therefore, cannot rise to certainty. 
 The judgments based on testimony and authority can at best reach 
 only a high degreee of probability. A judgment may be possible when 
 it is not probable. "A thing is said to be possible when, though not 
 actually in existence, all the conditions necessary for realizing its ex- 
 istence are given." It is possible, for example, that aerial transporta- 
 tion may some day take the place of transportation by steamer and 
 railway, but not perhaps probable. 
 
 The aim of the Practical Logic of Judgment should be 
 to train the thinker to skill in distinguishing clearly be- 
 tween the certain, the probable, and the doubtful ; and in 
 arriving at sound judgments, on the basis either of cer- 
 tainty or of probability, by which to govern the entire con- 
 duct of human life. 
 12 
 
Part III. 
 
 THE LOGIC OF REASONING OR THE SYLLOGISM. 
 
 The aim of the Logic of Eeasoning is to train the mind 
 to skill in dealing with the third Form of Thought. 
 
 Definition. — Reasoning is that form of thought in which 
 we compare various judgments and, on the ground of some 
 medium or cause, reach other judgments as inferences or 
 conclusions from them. Reasoning may, therefore, be used 
 as synonymous with Mediate Inference. The product of 
 reasoning, as embodied in language, is usually known as 
 the Syllogism. 
 
 Note.— Mediate inference is inference by a medium, or middle notion or term. 
 It is thus distinguished from immediate inference which, as has been seen (p. 
 121), does not make use of any such third or middle term. The middle term 
 is used where we cannot compare two things directly. We cannot compare 
 two lots directly by placing one upon the other, but we can measure them both 
 with a surveyor's chain, or other common measure, and thus ascertain their 
 relative dimensions. So when two notions or terms cannot be directly compared 
 and connected they may be indirectly by the use of a third notion or term. 
 We may, e. g., wish to connect " John Baptist" and " priest" in the judgment, 
 " John Baptist was a priest." Having no direct statement to that effect in the 
 Bible, we must reach the conclusion by reasoning from the fact that the sons 
 of priests were also priests. The process of thought is stated as follows : 
 
 Analytic Form. Synthetic Form. 
 
 f John Baptist was a priest ; ( The son of a priest was a priest ; 
 
 i For he was the son of a priest ; < John Baptist was the son of a priest ; 
 
 ( And the son of a priest was a priest. (. ,\ John Baptist was a priest. 
 
 Both terms are connected with a third term, " son of a priest," and thus 
 connected with each other. 
 
 134 
 
THE FORMATION OF REASONING. 135 
 
 The most helpful logical presentation of Reasoning must treat of 
 both the formation of reasonings or syllogisms and the unfolding of 
 syllogisms. The present subject will, therefore, embrace two Chapters. 
 
 CHAPTER L 
 
 THE FORMATION OP REASONING OR 
 
 MEDIATE INFERENCE, 
 
 The formation of thought as reasoning must manifestly 
 be placed at the foundation in all training to thought in its 
 third form. It will be necessary to consider, in successive 
 Sections, the nature of reasoning or mediate inference in 
 general, and the fundamental forms of reasoning, — deduc- 
 tion and induction. The process and the products will be 
 considered under each of the forms of reasoning. 
 
 Note. — Much of the modern depreciation of Logic, and especially of the 
 Logic of the Syllogism, is doubtless due to the fact that the Science has been 
 confined largely to the mechanical testing of barren forms. If this be all there 
 is in the Logic of Reasoning, it would have to be admitted that it is not a very 
 valuable means of knowledge; the old objection would hold, that " the prem- 
 ises, so far from being able to establish the truth of the conclusion, presup- 
 pose it." Take in illustration a syllogism commonly given: " All Cretans are 
 liars ; this man is a Cretan ; therefore he is a liar." How do we know all before 
 we know each f How do we know all before the character of this particular 
 Cretan is decided ? That is, until we are certain that this particular Cretan is 
 a liar, we cannot be certain that all Cretans are liars. 
 
 The all-important thing in reasoning is the finding of middle term* 
 «r connecting links of argumentation; and even the testing of the 
 various products of reasoning cannot proceed intelligently without 
 some skill in finding these connecting links. 
 
 Section L — Tie Process of Seasoning or Mediate Inference 
 
 in General. 
 Topic First. — The Forms of Reasoning. 
 
 All reasoning necessarily proceeds from general princi- 
 ples to particulars or individuals, or from facts or particu- 
 lars to general principles. Mediate Inference is, therefore, 
 
136 PRACTICAL LOGIC. 
 
 divided into two chief kinds : Deduction, or Specialization, 
 or Syllogism in the stricter sense ; and Induction, or Gen- 
 eralization, or Syllogism in the looser sense. 
 
 Syllogism in the stricter sense in its chief forms is inference from 
 the general to the particular or individual, and in all its forms infer- 
 ence proceeding from the general. Induction is inference proceeding 
 from the individual or particular to the general. Inference by anal- 
 ogy, which proceeds from the individual or particular to a co-ordinate 
 individual or particular, is a third form distinct from hoth, though 
 able to be reduced to a combination of the other two. See Ueberweg's 
 Logic, p. 333. 
 
 Deduction has also been called " the inference of subordination," or 
 "inference by analysis of notions;" induction, "the inference of su- 
 perordination ; " analogy, " the inference of co-ordination." 
 
 The difference between deduction and induction may be illustrated 
 by the methods of proving that the interior of the earth is in a molten 
 condition. From the volcanic phenomena, i. e., from the facts that 
 the earth is in a molten condition under Mount Vesuvius, Mount Hecla, 
 Mauna Loa, etc., it is inferred inductively that the whole interior is in 
 such condition. From the process of the earth's formation by the con- 
 densation of intensely heated material (an origin probable on astro- 
 nomical grounds), it is inferred deductively or syllogistically that the 
 interior is in a molten condition. The one process starts from facts ; 
 the other from a general principle. They are usually thrown into 
 syllogistic form, as follows : 
 
 Inductive Process. Deductive Process. 
 
 The interior of the earth is 
 molten ; 
 
 For, it is molten under Vesu- 
 vius, etc. ; 
 
 And Vesuvius, etc., fairly rep- 
 resents the whole. 
 
 The interior of the earth is 
 
 molten ; 
 For the solar system was formed 
 
 by condensation ; 
 And the earth is a part of the 
 
 solar system. 
 
 The nature of analogy, as made up of induction and deduction, may 
 be shown from the following example : " The Earth, a planet revolv- 
 ing in an orbit round our sun, turning on its axis, having an atmo- 
 sphere, change of seasons, etc., supports organic life; Mars is a planet 
 revolving in an orbit round our sun, turning on its own axis, having 
 an atmosphere, change of seasons, etc. ; hence Mars also will probably 
 support organic life." It will be seen by examination that this consists 
 
THE FORMATION OF REASONING. 137 
 
 of an apparent induction and a deduction combined. This may be 
 exhibited, in full, as follows : 
 
 The Earth supports organic life ; 
 
 The Earth is a planet revolving, etc., and fairly represents that 
 class of planets ; 
 .*. All planets revolving, etc., probably support organic life ; 
 r& [~ Mars is a planet so revolving, etc. ; 
 P [_.'. Mars probably supports organic life. 
 
 According to the common view both deduction and in- 
 duction may be embodied in syllogistic form (as in the 
 examples given). The elements of the reasoning, as em- 
 bodied in the syllogism, need, therefore, to be considered. 
 As the validity of the reasoning depends, however, not 
 upon the syllogistic forms, but upon the connecting link of 
 thought embodied in the middle term, the subject of find- 
 ing middle terms needs to be specially considered. 
 
 Note.— The question whether all reasoning can be reduced to the syllogism 
 is one into which we have not space to enter. Nor is there need to discuss it 
 here, since it is freely admitted that the validity of the reasoning depends upon 
 the connecting links of thought and not upon the form; and that the syllogism is 
 of no special value in the formation of processes of reasoning, but only in 
 formulating and testing them after they are formed. 
 
 Topic Second. — The Elements of Reasoning. 
 
 The elements of reasoning are ascertained by analyzing 
 the process as embodied in the Syllogism. The syllogism 
 is composed of three terms and three propositions ; and 
 underlying the form, as the real basis of thought, is some 
 mediating notion or cause. 
 
 I. The Terms and Propositions. 
 
 The terms or notions in the syllogism are distinguished 
 as the major term, the minor term, and the middle term. 
 The propositions in the usual form of statement are the 
 major premise and the minor premise, constituting the ante- 
 cedent or proof, and the conclusion or consequent. 
 
 The conclusion is the judgment to be proved. In the formal syllo- 
 gism it is placed last. Its subject, represented by S, is the minor term ; 
 12* 
 
138 PRACTICAL LOGIC. 
 
 its predicate, represented by P, is the major term. The middle term, 
 
 represented by M, is that with which the major and minor are com- 
 pared in the premises. 
 
 The major premise is the judgment in which the major term or 
 predicate of the conclusion is compared with the middle. 
 
 The minor premise is the judgment in which the minor term is 
 compared with the middle. 
 
 This may be illustrated in concrete form and in formula, as follows : 
 
 M is P ; Major Premise. 
 S is M ; Minor Premise. 
 .-. S is P. Conclusion. 
 
 All conquerors (M) are tyrants (P) ;" 
 Napoleon (S) was a conqueror (M) ; 
 Napoleon (S) was a tyrant (P). 
 
 The conclusion is reached by comparison of both its terms 
 with the third or middle term, " conqueror." 
 
 II. The Middle Term or Connecting Link. 
 
 The middle notion or term (originally called the argu- 
 ment) always- represents the link of thought by which the 
 two terms of the conclusion are brought together and the 
 judgment proved. It furnishes the sufficient reason for 
 connecting the major and minor terms. Reasoning is prop- 
 erly, therefore, finding* the sufficient reason— in case of in- 
 duction the cause 1 — for the connection of the terms in the 
 conclusion. 
 
 Various maxims have been formulated to express the connection 
 embodied or implied in the middle term. The principal are those of 
 Aristotle and Kant, which apply respectively to propositions of extent 
 and content, or to propositions made up of class terms and those 
 made up of attribute terms. The axiom of Sufficient Reason, or of 
 Reason and Consequent, is, however, the best and most complete 
 expression of this connection. 
 
 The so-called dictum of Aristotle places the relation of genus and species at 
 the foundation of reasoning. Whatever can be predicated affirmatively or 
 negatively of any genus or class distributed can be predicated likewise of all 
 or any of the species or individuals included under it. If it can be affirmed 
 of the genus man, that it is included in the higher genus person, then it can 
 be affirmed of the species slaves, included under man, that it is included under 
 person. Or if it can be affirmed of the genus man, that it is excluded from the 
 genus brute, then the same can be affirmed of the species poets, included under 
 the genus, man. 
 
THE FORMATION OF REASONING. 139 
 
 The formula of Kant places the relation of a complex property to its compo- 
 nents at the foundation of reasoning. Whatever is a component of a complex 
 property of a thing is a property of the thing itself. The mark brave, which 
 is a component of the complex mark conqueror, is also a mark of Caesar, 
 the object to which the complex conqueror applies. 
 
 Others make the relation at the basis of reasoning that of whole and part. A 
 part of a part is also a part of the whole. 
 
 The real connecting principle or basis in reasoning, i. e., the real 
 sufficient reason, is, perhaps, best expressed by the relation of reason 
 and consequent, which, as has already been seen (p. 20), embraces 
 whole and part, cause and effect, substance and attribute, genus and 
 species, etc. Any form of reason and consequent may be at the basis 
 of deduction; while the basis of induction is the strictly causal rela- 
 tion only. 
 
 Topic Third. — Finding and Verifying Arguments or Mid- 
 dle Terms. 
 
 From what has been thus far considered, it is obvious 
 that reasoning essentially consists in finding and verifying 
 arguments, or middle terms and causes, under the principle 
 of Sufficient Reason or Reason and Consequent. This pro- 
 cess differs in deduction and induction, inasmuch as these 
 forms of reasoning differ. 
 
 Section II.— Deductive Seasoning. 
 
 Topic First. — Process of Finding and Verifying the 
 Argument in Deduction. 
 
 Three things are essential in deduction: first, finding the 
 proper middle term ; second, verifying the premises formed 
 by the aid of it ; third, testing the conclusion. 
 
 I. Finding the Middle Term. 
 
 The first question is, By ivhat middle term can the two 
 given terms be bound together or disjoined in the conclu- 
 sion ? The following Rules will guide the thinker in his 
 quest : 
 
 Eule 1st. — Examine carefully, by the principles laid down in the 
 Logic of Conception, the two terms to be connected or disjoined, in 
 
140 PRACTICAL LOGIC. 
 
 order to ascertain which of the relations under reason and consequent 
 is applicable to them. 
 
 Kule 2d. — Seek the proper mediating whole, concept proper, class, 
 or cause, as the case may require. 
 
 Rule 3d. — Bring the middle term thus found into proper connection 
 with the other terms and these with each other in syllogistic statement. 
 
 The application of these Rules may be illustrated by examples. 
 Thus, in seeking a middle term to prove that "The Persians worship a 
 thing insensible" we find, by the first Eule, that this term must be an 
 individual under the genus, " things insensible." By the second Rule, 
 11 the sun " furnishes such an individual. By the third Rule, these 
 are brought together in syllogistic statement, in the order of proof, as 
 follows : 
 
 The Persians worship a thing insensible ; Question. 
 For the Persians worship the sun ; J _ 
 
 And the sun is a thing insensible, i 
 
 Again, in finding a middle term to prove that " Judas was not a true 
 apostle" we find, by the first Rule, that the major term, "true apos- 
 tle," is a genus or class term. By the second Rule, "thief" furnishes 
 a "genus" excluded from the genus, "true apostle." By the third 
 Rule, this takes shape as follows : 
 
 Judas was not a true apostle ; Question. 
 
 For Judas was a thief ; | p , 
 
 And no thief was a true apostle. J 
 Once more, in proving that "Plato is mortal," we find, by the first 
 Rule, that the major term, "mortal," is a concept or attribute term. 
 By the second Rule, we find that the complex concept, " man," in- 
 cludes "mortal" as a component property; and, therefore, since the 
 mark of a mark is a mark of the thing itself, "mortal" is a mark of 
 " Plato." By the third Rule, this gives, stated in twofold syllogistic 
 form: 
 
 r Plato is mortal ; Question. r Man is mortal ; \ p r 
 
 < For Plato is a man ; 'I 1 Plato is a man ; J 
 
 I And man is mortal. / ■'" I .'. Plato is mortal. Conclusion. 
 
 II. Verifying the Premises. 
 
 When the middle term has thus been found and con- 
 nected with the major and minor terms, the question arises, 
 Are these premises true ? Hence the following Rule : 
 
THE FORMATION OF REASONING. 141 
 
 Rule 4th. — Test the premises by the principles already presented 
 for the verification of judgments (p. 98), in order to be sure that only 
 correct judgments have been grasped. 
 
 It is all important that correct judgments should be grasped and 
 placed at the foundation as premises, since otherwise any inferences 
 from them would be logically worthless. The sources of the judgments 
 made use of in deduction are the following : intuition ; thought proper 
 inductive and deductive; and testimony and authority. The prem- 
 ises must be tested by the principles by which judgments from these 
 various sources are proved. 
 
 III. Testing the Conclusion. 
 
 When the premises have been found to be true or prob- 
 able, the question arises, Does the conclusion follow from 
 the premises ? Hence the following Rule : 
 
 Rule 5th. — Test the whole process by the principles of analysis pre- 
 sented in the Logic of Conception, and by the laws which govern the 
 Syllogism as presented in the next Chapter under the Unfolding of 
 Reasoning. 
 
 Partial understanding of the terms may lead to false conclusions. 
 This may be prevented by a careful study and analysis of the con- 
 cepts and terms involved, by means of Partition, Division, and Defi- 
 nition. False conclusions may also be drawn from correct premises. 
 This may be prevented by the careful use of the formal rules of the 
 Syllogism. 
 
 In all deductive reasoning, it should be remembered, 
 that the conclusion can never be any more certain than the 
 premises. Forgetfulness of this is the source of many and 
 great errors in both Science and Philosophy. 
 
 Topic Second. — Products of Deductive Reasoning. 
 
 The product of deduction is the Syllogism proper in : 
 various forms. Syllogisms are divided, by the form of tiu 
 judgments embodied in them, into categorical and hypo- 
 thetical. Categorical syllogisms are either simple or com- 
 bined, — simple when they contain but one argument with 
 its major and minor premises expressed or understood and 
 its conclusion ; combined when more than one process of 
 
142 PRACTICAL LOGIC 
 
 argument is involved. The former may be called the mono- 
 syllogism ; the latter the polysyllogism. 
 
 I. Categorical Syllogisms. 
 
 A categorical syllogism is one in which the judgments 
 are categorical (p. 117). 
 
 1. The monosyllogism may be in its statement either 
 complete or incomplete. 
 
 The complete form is the ordinary form in which both the premises 
 and the conclusion are expressed. The incomplete form or the enthy- 
 meme (Greek, meaning in the mind) is that form in which one premise 
 is unexpressed, or left to be supplied by the mind. Thus : 
 
 11 Alexander the Great was brave ; 
 For he was a conqueror." 
 
 In this case the major premise, "All conquerors are brave," is omitted. 
 The minor premise may also be omitted. Thus : 
 " Conquerors are brave; 
 Therefore Alexander the Great was brave." 
 
 Note.— The enthymeme is the usual form in ordinary speech. The .premise 
 left unexpressed is easily supplied in completing the syllogistic statement. 
 It will also be seen that in common speech there are to be found many abridged 
 and disguised forms of argument. For example : " Hard study strengthens the 
 mind, but wearies the flesh ; so that what wearies, strengthens ; " " Theft is a 
 crime ; yet some kinds were legal in Sparta." In such cases the first step is to 
 reduce the argument to the normal form. 
 
 2. The polysyllogism includes the various forms in which 
 • separate syllogisms are combined into wholes of connected 
 
 reasoning. Syllogisms may be attached, as prosyllogisms, 
 to premises to prove them, or, as episyllogisms, to conclu- 
 sions, making the conclusions premises for reaching further 
 conclusions. In the former case the prosyllogisms are sub- 
 ordinate to a principal syllogism, and the whole constituted 
 is, therefore, a complex syllogism, which may be known as 
 the epichirema; in the latter case the episyllogisms are 
 co-ordinate with that to which they are attached, and the 
 whole is, therefore, a compound syllogism. 
 
 (1.) The Complex Syllogism, or Epichirema, or reason-rendering 
 
THE FORMATION OF REASONING. 143 
 
 syllogism, is either manifest (i. e., having all the parts fully expressed), 
 or occult (i. e., having some of the parts suppressed). Both the mani- 
 fest and occult forms may be "either single or double, according as 
 one or both of the premises are furnished with an auxiliary reason." 
 
 The single epichirema, in both its occult and manifest forms, may be illus- 
 trated by the following example : 
 
 Main Syllogism. Occult Prosyllogism. Expanded Prosyllogism. 
 Vice is odious ; ( Whatever enslaves is a vice ; 
 
 Avarice is a vice, for [it enslaves ;] J Avarice enslaves ; 
 /.Avarice is odious. ( /.Avarice is a vice. 
 
 Omitting the expanded prosyllogism, we have the ordinary single epichi- 
 rema in its occult form ; omitting the occult prosyllogism, we have the same 
 in its manifest form. 
 
 The double epichirema, in both its occult and manifest forms, may be illus- 
 trated by the following example : 
 
 Main Syllogism. Occult Prosyllogisms. Expanded Prosyllogisms. 
 Man has a spirit ; for [he is rational ; =] r Every rational being has a 
 
 ) spirit; 
 
 ~\ Man is a rational being ; 
 (. .*. Man has a spirit. 
 Man has a body; for [he fills space; =] c Whatever fills space has a 
 
 J body; 
 *j Man fills space ; 
 .*. Something that has a spirit has body. C •*. Man has a body. 
 
 Omitting the expanded prosyllogisms, we have the double epichi- 
 rema in its occult form ; omitting the occult prosyllogisms, we have 
 the same in its manifest form. 
 
 (2.) The compound syllogism, made up of successive co-ordinate 
 syllogisms, includes the double syllogism, in which the episyllogism 
 is attached to the conclusion of a syllogism, making that conclusion a 
 premise for reaching a new conclusion ; and the chain syllogism, 
 which is made up of successive co-ordinate syllogisms. In both these 
 forms it may be either manifest or occult. 
 
 The double syllogism of the compound form does not need to be 
 further subdivided. The chain syllogism in its occult form is usually 
 known as the sorites (Greek, meaning a heap). The successive syllo- 
 gisms in it are all equally abridged. 
 
 Both the manifest and occult forms may be illustrated by the following ex- 
 amples, in which the occult forms are contractions of the manifest forms : 
 
 Double Syllogism, Manifest Form. 
 r Useful studies ought to be pursued ; 
 1st. -j Logic is a useful study ; 
 I ,\ Logic ought to be pursued. 
 
144 PRACTICAL LOGIC. 
 
 r A course which omits what ought to be studied is deficient : 
 2d. \ A course which omits Logic omits what ought to be studied ; 
 I .". A course which omits Logic is deficient. 
 
 Double Syllogism. Occult Form. 
 
 Useful studies ought to be pursued ; ] . 
 Logic is a useful study ; Y ™* in . 
 
 .• Logic ought to be pursued ; J s y"°g lsm - 
 
 Hence an educational course 1 . . 
 
 which omits Logic is deficient. / Episyllogism. 
 
 Chain Syllogism, Occult, Sorites. Chain Syllogism, Manifest. 
 
 Bucephalus is a horse ; I. f Bucephalus is a horse ; 
 
 A horse is a quadruped ; 
 Bucephalus is a quadruped. 
 
 Bucephalus is a quadruped ; 
 A quadruped is an animal ; 
 Bucephalus is an animal. 
 Bucephalus is an animal ; 
 An animal is a substance ; 
 Bucephalus is a substance. 
 
 A horse is a quadruped ; II. 
 
 A quadruped is an animal ; III. 
 An animal is a substance ; 
 , Bucephalus is a substance. 
 
 The sorites proper is of two kinds, — the progressive or Aristotelian, 
 in which the argument descends from whole to part ; and the regres- 
 sive or Goclenian, in which the argument ascends from part to whole, 
 as in the following examples : * 
 
 Progressive Sorites. Regressive Sorites. 
 
 Bucephalus is a horse ; An animal is a substance ; 
 
 A horse is a quadruped ; A quadruped is an animal ; 
 
 A quadruped is an animal ; A horse is a quadruped ; 
 
 An animal is a substance ; Bucephalus is a horse ; 
 
 /. Bucephalus is a substance. /. Bucephalus is a substance. 
 
 The sorites can thus readily be expanded into a manifest compound 
 syllogism. It consists of "as many simple syllogisms as there are 
 middle terms between the subject and predicate of the conclusion, i. e., 
 intermediate wholes and parts between the greatest whole and the 
 smallest part, which the reasoning connects.'* In the example given, — 
 taking the progressive form, — the greatest whole and smallest part are 
 substance and Bucephalus; the middle terms are horse, quadruped, 
 animal. This gives three simple syllogisms, by using successively 
 these middle terms. 
 
 II. Hypothetical Syllogisms. 
 
 The hypothetical syllogism is that form of syllogism in 
 which the reasoning turns upon some hypothetical judg- 
 ment (p. 117) embodied in the major premise. Hypotheti- 
 
THE FORMATION OF REASONING. 145 
 
 cal syllogisms, whether monosyllogisms or polysyllogisms, 
 are, therefore, primarily divided into conditional or con- 
 junctive and disjunctive. These, as in the case of cate- 
 goricals, may be either manifest or occult. 
 
 1. A hypothetical monosyllogism is one which contains 
 but one argument, with its major and minor premises ex- 
 pressed or understood, and its conclusion. The suppressed 
 or disguised premise gives the hypothetical enthymeme 
 which is the most common form in ordinary speech. Both 
 manifest and occult hypothetical arguments may be either 
 conditional or disjunctive. 
 
 (1.) A conditional, or conjunctive hypothetical syllogism is one in 
 which the reasoning turns upon a conditional or conjunctive judg- 
 ment embodied in the major premise. This may be illustrated in both 
 its manifest and occult forms by the following example : 
 
 Manifest Form. Enthymeme. 
 
 5 If rains are plenty, the crops wiU be C If rains are plenty, crops will be 
 plenty ; J plenty ; 
 
 ) Rains are plenty: j 
 
 v .*. Crops will be plenty. V So crops will be plenty. 
 
 (2.) A disjunctive hypothetical syllogism is one in which the rea- 
 soning turns upon a disjunctive judgment embodied in the major 
 premise. This may be illustrated by the following example : 
 
 Manifest Form. Enthymeme. 
 
 Man is either an automaton or free ; ( Man is either an automaton or free ; 
 
 { 
 
 He is a free being ; ^ 
 
 .-. He is not an automaton. I And so he is assuredly free. 
 
 2. The hypothetical polysyllogism includes the various 
 forms in which hypothetical arguments may be brought to- 
 gether into wholes of connected reasoning. These wholes 
 may arise from combining hypotheticals and disjunctives 
 in the premises, or by combining entire arguments. The 
 former gives rise to dilemmatic syllogisms ; the latter to 
 compound hypothetical syllogisms, including the double 
 form and the sorites. 
 
 (1.) A dilemmatic syllogism is one having a dilemmatic judgment 
 (p. 118) for its major premise, with a minor premise so affirming or 
 13 K 
 
146 PRACTICAL LOGIC. 
 
 denying some member or members of the major as to lay the founda- 
 tion for an inference. The forms depend upon the various combina- 
 tions in the major premise. The combinations are as follows : 
 
 1st. A single conditional antecedent with a disjunctive consequent, 
 as in the example : 
 
 If the Senator aspires to a place, he will either rule or ruin : 
 The Senator aspires to the place of President : 
 .*. He will either rule or ruin. 
 Or, If A is B. either C is D or E is F ; 
 
 But A is B, ... .'. either C is D or E is F. 
 
 2d. A plurality of conditional antecedents all having one common 
 
 consequent, as in the example : 
 
 " If things are what we can help, we ought not to fret about them ; and if 
 they are what we cannot help, we ought not to fret about them ; 
 
 But all things are either what we can or cannot help ;, 
 ,\ They are what we ought not to fret about." 
 
 Or, If A is B, X is Y, and if C is D, X is Y; 
 But either A is B or C is D ; ... /. X is Y. 
 
 This form is what has been known as the dilemma in the strict sense, 
 or the horned syllogism. It is so called because it confronts an oppo- 
 nent with two assumptions, on which it tosses him as on horns from 
 one to the other, each being equally fatal to him. 
 
 3d. A plurality of conditional antecedents each with its .own con- 
 sequent, as in the example : 
 
 f If men are virtuous they are wise, Or, If A is B, C is D, \ 
 
 \ And if they are vicious they are unwise ; And if E is F, G is H ; / 
 
 But they are either virtuous or vicious ; But either A is B, or E is F ; 
 ,\ They are either wise or unwise. .'. Either C is D, or G is H. 
 
 (2.) The compound hypothetical syllogism includes the double form, 
 
 in which the latter of two syllogisms is abridged, and appears as an 
 episyllogism ; and the hypothetical sorites, in which the successive 
 syllogisms are all equally abridged. These may be illustrated by ex- 
 amples : 
 
 Double Form, 
 f If the people are industrious, wealth increases; 
 J They are industrious ; Episyllogism. 
 
 ( .*. Wealth is increasing (and hence the nation will become powerful). 
 Hypothetical Sorites. 
 If Gladstone is virtuous, he is brave ; Or, If A is B, C is D ; 
 
 If brave, he is magnanimous ; If C is D, E is F ; 
 
 If magnanimous, he will relieve the Irish ten- \ if E is F G is H • 
 
 ants ; J 
 
 But he is virtuous, and .*. will relieve the Irish \ B ^ . B • g is H 
 
 tenants. J 
 
THE FORMATION OF REASONING. 147 
 
 Praxis. — Find middle terms for the following conclusions, according 
 to the Rules given ; verify the premises and test the conclusion ; and 
 mark by the appropriate vowels the quantity and quality of all the 
 judgments : 1. Jupiter is a planet. 2. Education is valuable. 3. 
 Religion is indispensable. 4. The crocodile is a reptile. 5. Few 
 patriots have been disinterested. 6. No brutes are responsible. 7. 
 Perseverance is a condition of success. 8. A sensualist is not truly 
 free. 9. The elk is ruminant. 10. Good logicians are not true poets. 
 11. The immoral man is not happy. 12. The inactive man cannot be 
 happy. 13. Astrology is not a science. 14. Astronomy is a science. 
 
 Give a complete outline of the kinds of Syllogisms, as presented in 
 the preceding Section, and then construct one or more original syllo- 
 gisms illustrating each of the kinds. 
 
 Section III.— Inductive Seasoning. 
 
 Topic First. — Process of Finding and- Verifying the Cause 
 in Induction. 
 
 Two things are essential in induction : first, fixing upon 
 some assumed cause which works in the facts from which 
 the inference is sought, and which furnishes the basis for 
 a working hypothesis; second, testing and verifying this 
 hypothesis. 
 
 Note.— Ueberweg has said truly : " Hypotheses are necessary in aU sciences 
 if the knowledge of causes is to be reached. Causes as such are not accessible 
 to observation, and, therefore, at first can be thought only under the form of 
 hypotheses, until, with the advance of the sciences, the previously problem- 
 atic suppositions pass over into knowledge apodictically certain. . . Scientific 
 hypotheses . . . are the results of regular reflection on experience, and, as 
 premises in tentative deductions, form the necessary preliminaries to ade- 
 quate knowledge." 
 
 I. Finding the Working Hypothesis. 
 
 In finding the cause in induction, the first question to be 
 asked is, What working hypotheses, in themselves possible, 
 can be formed, which agree with the facts of experience, so 
 that the phenomena may all be taken into account and ex- 
 plained ? 
 
 Induction derives its data from experience. Experience is the ex- 
 amination which is necessary to furnish us the facts from which to 
 
148 PRACTICAL LOGIC 
 
 make inferences. Such experience is obtained either by observation or 
 by experiment. 
 
 Observation is the act of the mind in seizing upon facts as they are sponta- 
 neously presented in nature. Its nature and methods have already been 
 unfolded (p. 26). Experiment is the process of voluntarily " putting in action 
 causes and agents over which we have control, and purposely varying their 
 combinations and noticing what effects take place." It vastly multiplies the 
 possibilities of observation, and is thus of the greatest importance to science. 
 The data drawn from experience for use in induction consist of facts or phe- 
 nomena. A phenomenon means literally " that which appears to, or is known 
 directly by, the senses," and then " that which is known as a fact to the mind." 
 The word, therefore, includes all facts whether made known by the senses or 
 consciousness. The word fact is substantially its equivalent in usage. It sig- 
 nifies literally " something done," and may be defined to be anything that 
 exists or happens, whether in the world of matter or of mind. 
 
 Equally important with the data of induction is the correct logical 
 method of dealing with the facts. This Bacon sought to furnish in 
 his Novum Organum or New Instrument. Its aim is to direct the mind 
 in seizing upon the facts in any given region, constructing hypotheses 
 for their explanation, and, through the verification of these, reaching 
 perfected theories or general truths. 
 
 " The correct construction of hypothesis," says Ueberweg, " is a 
 life and death question with Philosophy ; for it is the science of the 
 principles which underlie all the sciences, and requires more than 
 any other to pass beyond mere experience, and to bring together by 
 comparison very different departments of knowledge." Hence the 
 importance of correct Rules carefully applied. 
 
 Eule 1st. — Observe, analyze, and classify the facts to be generalized 
 and explained, in order to ascertain their reality and their various 
 elements and relations. 
 
 This Rule guards against two common sources of error in induction. The 
 first is that of assuming what is not fact to be fact. This is illustrated by the 
 problem presented by Charles II. to the Royal Society : " Why does a live fish 
 in water increase the weight while a dead fish does not?" The answer to the 
 question, " Is it a fact ?" would have saved the time spent in endeavoring to 
 solve the imaginary problem. The second is the error from getting only a 
 partial view of the facts or from failure to get them in their relations. This is 
 illustrated in Stahl's method of accounting for combustion, by the extrication 
 of a substance supposed to be contained in all combustible matter, called 
 phlogiston, which went up in the flame. Combustion results in the visible 
 residue of ashes and the invisible phlogiston which passes off. The error was 
 in the non-observation of an important part of the actual residue,— the gas- 
 eous products of combustion. When these were at last taken into account, it 
 was found that the gases with the ashes weighed much more than the sub- 
 stance burned, so that there was no room for phlogiston. See Mill's Logic, 
 BookV.,Ch,iv, 
 
TEE FORMATION OF REASONING. 149 
 
 Rule 2d. — Correctly interpret the facts, i. e., seek to find the appro- 
 priate cause for the facts and basis for the generalization. 
 
 By cause in induction is meant " operating power," or, more 
 strictly, "power which in operating originates new forms of being." 
 It is anything which has efficiency and exerts it in producing change, 
 and hence is often called efficient cause. It should be carefully dis- 
 tinguished from law, which has no efficiency, but is merely an expres- 
 sion of an established sequence of facts, or of the regular order in 
 which a cause operates. A condition is "that which is prerequisite 
 in order that something may be, and especially in order that a cause 
 may operate." It is " prior to the production of an effect; but it does 
 not produce it. It is fire that burns ; but, before it burns, it is a 
 condition that there be an approximation of the fire to the fuel, or 
 the matter that is burned. . . The cause of burning is the element of 
 fire, fuel is the con-cause, and the condition is the approximation of 
 the one to the other." 
 
 The cause may be sought, first, in some known, or, secondly, in some un- 
 known, force or forces. The search in the former case has to do with some 
 real cause and is guided by the so-called Methods of Induction, and in the 
 latter case must be reached by inductive assumption or assumption of strictly 
 hypothetical cause. In the former case the results tend to take shape in contri- 
 butions to exact science; in the latter they belong to the region of scientific 
 question or metaphysical speculation. The quarrels of scientists and theolo- 
 gians very often arise from confounding the two. 
 
 (1.) Inductions of Real Cause. — The Canons of the In- 
 ductive Method used in the search for the real cause for 
 any phenomenon, whether that cause is simple or complex, 
 may have reference either to the preliminary consideration 
 of the happening or not happening of the event, the cause of 
 which is sought; or to the more advanced problem of meas- 
 uring the exact quantity of an effect, if it be capable of being 
 more or less, and connecting it with the quantity of the cause. 
 To the first stage belong the methods of agreement and of 
 difference ; to the second, the methods of concomitant vari- 
 ation and of residues. 
 
 A. What can be learned of the real cause of an event 
 from the happening or not happening of that event ? 
 
 The Method of Agreement is applied in case of the uniform hap- 
 pening of an event. This gives rise to — 
 13* 
 
150 PRACTICAL LOGIC. 
 
 Canon First. — If in all observed cases of an effect or phenomenon 
 one condition is uniformly present, that is probably the cause, or in- 
 cludes the cause, of the phenomenon or effect. In other words, " the 
 sole invariable antecedent of a phenomenon is probably its cause" 
 
 u To apply this method we must collect as many instances of the phenom- 
 enon as possible, and compare together their antecedents. Among these the 
 causes will lie, but if we notice that certain antecedents are present or absent 
 without appearing to affect the result, we conclude that they cannot be neces- 
 sary antecedents." 
 
 The method of agreement is subject to a serious difficulty. An antecedent 
 may not be a cause. Night or the cock-crowing or the rising of some diligent 
 workman may uniformly precede the coming of- the day without being the 
 cause of it. Hence the necessity for tests by which to distinguish between 
 simple antecedent and real cause. 
 
 The Method of Difference is applied in case of the uniform happen- 
 ing of an event in the case of the presence of some condition, and the 
 uniform failure of it in case of the absence of that condition. This 
 gives rise to 
 
 Canon Second. — If, in all instances in which a phenomenon does 
 occur, one single condition is present, which is uniformly absent 
 whenever such phenomenon does not occur, this constantly present or 
 absent condition is presumed to be the cause of the phenomenon. 
 
 Thus we can clearly prove that friction is one cause of heat, because when 
 two sticks are rubbed together they become heated ; when not rubbed they do 
 not become heated. Sir Humphrey Davy showed that even two pieces of ice 
 w T hen rubbed together in a vacuum produce heat, as shown by their melting, 
 and thus completely demonstrated that the friction is the source and cause 
 of the heat. We prove that air is the cause of sound being communicated to 
 our ears, by striking a bell in the receiver of an air-pump, as Hawksbee 
 first did in 1705, and then observing that when the receiver is full of air we 
 hear the bell ; when it contains little or no air we do not hear the bell. 
 
 B. What can be learned of the Real Cause of an event 
 from the varying degree or quantity of an event ? 
 
 11 Every science and every question in science is," as Jevons has 
 said, " first, a matter of fact only, then a matter of quantity, and by 
 
 degrees becomes more and more precisely quantitative. Thirty years 
 ago most of the phenomena of electricity and electro-magnetism were 
 known merely as facts ; now they can be for the most part exactly 
 measured and calculated. 
 
 " There is in fact a natural course of progress through which we 
 proceed in every such inquiry, as may be stated in the following se- 
 ries of questions. 
 
THE FORMATION OF REASONING. 151 
 
 1. Does the antecedent invariably produce an effect ? 
 
 2. In what direction is that effect? 
 
 3. How much is that effect in proportion to the cause ? 
 
 4. Is it uniformly in that proportion ? 
 
 5. If not, according to what law does it vary ? " 
 
 The Method of Concomitant Variations is applied, after phenomena 
 begin to be measured, in cases where there is an increase or decrease of 
 an event with a corresponding increase or decrease of the condition 
 which, by the other methods, has been assumed to be the cause. This 
 gives rise to 
 
 Canon Third. — Increase or diminution of t"he effect, accompanied by 
 the increased or diminished intensity of the assumed cause, in cases 
 which admit of increase and diminution, increases the assurance of 
 the causal relation. 
 
 By the method of difference it may be shown that air is the cause of the 
 transmission of sound, by striking a bell in the air and in a vacuum. Instead 
 of this, the method of concomitant variations may be applied, by striking a 
 bell in the receiver of an air-pump with a very little air, and then increasing 
 and decreasing the density of the air. The sound, which is very faint with a 
 little air, grows fainter and disappears as the air is exhausted, and becomes 
 louder and fuller as air is added. 
 
 This method is made use of in seeking causes for events which go through pe- 
 riodic changes, alternately increasing and decreasing. It leads us to search for a 
 cause which undergoes like periodic changes. The tides are thus proved to 
 be due to the combined attraction of the moon and sun, since the periods of 
 high and low, spring and neap, tides succeed each other in intervals corre- 
 sponding to the apparent revolutions of those bodies round the earth. 
 
 But all these methods are subject to difficulty from the fact that 
 causes are usually complex, or, in other words, that there is usually 
 a plurality of causes co-operating in the production of any given 
 effect. This gives rise to 
 
 The Method of Residues or of Eesidual Variations. — When there 
 are several causes each producing a part of the effect, we desire to 
 know how much is due to each cause. This lea :" ; t : 
 
 Canon Fourth. — Subtract from any phenomenon such part as is 
 known bv previous inductions to be the effect of certain of the causes, 
 and the residue of the phenomenon is the effect of the remaining causes. 
 
 This is illustrated by the method of ascertaining the exact weight of a load 
 of hay or any other commodity in a cart, by weighing the cart and load to- 
 gether, and then subtracting the tare or weight of the cart alone, previously 
 ascertained. Almost all the remarkable modern predictions in astronomy 
 have been made by the use of the method of residues. Thus, after the effects 
 of all known attractions were calculated in the case of Uranus, it was stili 
 
152 PRACTICAL LOGIC 
 
 found that the planet was sometimes before and sometimes behind its calcu- 
 lated place. This residual effect pointed to the existence of some cause of 
 attraction not then known, and the exact place and size of the disturbing 
 body was calculated and the planet Neptune discovered. 
 
 " The motions of several comets have in this way been calculated, but it 
 is observed that they return each time a little later than they ought. This re- 
 tardation points to the existence of some obstructive power in the space 
 passed through, the nature of which is not yet understood." 
 
 When the same phenomenon may be the effect of any one of various 
 causes, there arises the necessity for excluding all the causes but that 
 which really operates in the given case. Ordinarily this is not a 
 difficult matter. It requires, however, that the attendant circum- 
 stances should be carefully noted and understood. A room may be 
 heated by the August sun, or by a fire in furnace or grate or stove, or 
 by any one of various other causes. Which is the operating cause 
 may be ascertained by the proper inspection, the real cause being 
 thus found and all others excluded. 
 
 (2.) Inductions of Hypothetical Cause. — When the cause 
 of any given phenomenon is unknown or beyond our reach, 
 the assumption of some hypothetical cause becomes a ne- 
 cessity of the human mind. Such cases are in the region 
 of tentative science or scientific speculation, rather than in 
 that of exact science. Rule 2d requires in such cases that 
 the cause or causes assumed should be appropriate and ade- 
 quate to account for all the facts. 
 
 Rule 3d. — When the facts have been sufficiently investigated com- 
 bine them all under the cause, simple or complex, which seems best 
 suited to produce them, and which is at work in all similar facts. 
 This gives the working hypothesis, which must be modified to suit the 
 farther developments of investigation. 
 
 As the observation may be more or less complete, various working 
 hypotheses may be reached by the same thinker or by different 
 thinkers. 
 
 When the facts concerning the movements of bodies on the earth and in the 
 heavens have been to some extent observed, they may be referred to gravity 
 as the cause. When the investigation has been carried still further, the work- 
 ing hypothesis of universal gravitation, of Newton, may be stated : "Any two 
 masses in the universe, whatever their material, attract each other by gravitation with 
 a force which varies directly as the mass and inversely as the square of the dis- 
 tance" 
 
THE FORMATION OF REASONING, 153 
 
 This is the work of the constructive imagination or of 
 the power of scientific construction, and must always pre- 
 cede complete and established scientific theory. 
 
 II. Testing the Working Hypothesis. 
 
 Scientific thinking requires that to the most ingenious 
 boldness in forming working hypotheses should be united 
 the most cautious accuracy in testing them before their 
 acceptance as truth. The tests of hypotheses are found in 
 connection with the cause assumed, the facts to be explained, 
 or the application of the deductive method. 
 
 11 A riper inquiry," says Ueberweg, " recognizes that in all problems where 
 we must proceed upon mere observation, and not with mathematical certainty, 
 the scientific correctness of distinct hypotheses must be the first object of 
 investigation. An essential advance in method in this sense was made in 
 Astronomy, when in the Platonic school, and especially by Heraclides of Pon- 
 tus, the question to be investigated was not stated in this way : What positions 
 and motions of the heavenly bodies are to be necessarily accepted on empir- 
 ical and speculative grounds? but in this : What hypotheses of regular motions, 
 in themselves possible, can be formed which agree with the facts of observa- 
 tion, so that the phenomena may be ' preserved'?" 
 
 Rule 1st. — See that the hypothesis in each case embodies a cause 
 or complex of causes which is appropriate, sufficient, and, if possible, 
 known and true. This is the cause test. 
 
 All rival hypotheses should be considered and fairly tested accord- 
 ing to this Rule. The direction of Ueberweg is as follows : " Let all 
 the opposing fundamental opinions be brought under the view of dif- 
 ferent thoroughly testing hypotheses, and do not let the one opinion 
 (as too often happens if it is the traditional one) be treated from outset 
 as correct, necessary, sound, and rational, and those of opponents con- 
 sidered to be false, arbitrary, unsuitable, or foolish." 
 
 The Rule suggests various particulars to be noted in settling the 
 claims of rival hypotheses. 
 
 1st. The hypothesis which is to be of service must embody a cause. 
 
 The hypothesis of evolution, as stated by Spencer, embodies no cause : " Evo- 
 lution is a change from an indefinite, incoherent homogeneity to a definite, 
 coherent heterogeneity through continuous differentiations and integration." 
 41 A change " is not a cause, but is rather the very thing to be explained. This 
 is true of a vast region of so-called inductions, which are not inductions at all, 
 because there is no cause at the foundation of the facts. For example, it might 
 readily be concluded, from the fact that man and all the animals with which 
 
154 PRACTICAL LOGIC. 
 
 we come in contact move the lower jaw in masticating food, that all animals 
 do the same. The fact, however, is that the crocodile moves the upper jaw. 
 This is mere generalization, and not induction in the proper sense. 
 
 2d. The hypothesis is to be preferred which embodies an appro- 
 priate oause. 
 
 The universe is found by scientific investigation to be a thought-system. Of 
 various hypotheses concerning its production, — by chance, by self-origination 
 through blind matter and force, by an Intelligent Author capable of planning 
 and constructing such a thought-system, etc.,— the hypothesis of an Intelli- 
 gent Author is the only scientific one, since such a cause is the only appro- 
 priate one for the effect. 
 
 3d. The hypothesis is to be preferred which embodies a known 
 cause. 
 
 Induction assumes the simplicity of nature. That is, the Author of nature 
 works as man would work, using the simplest means to attain the end in view, 
 never introducing a new force where some already existing force will accom- 
 plish the object. On this principle Newton extended the familiar action of 
 the known force of gravity on the earth's surface to the phenomena of the 
 heavens. 
 
 4th. The hypothesis is to be preferred which embodies a true cause. 
 
 Newton's view of gravitation made use of a true cause, which " had been 
 already known as an actual power in nature, in the power of weight upon the 
 earth." 
 
 When no known agent can be found, it becomes necessary to assume some 
 unknown, but appropriate and adequate, cause. Thus, the physicist in 
 accounting for the phenomena of light, electricity, etc., assumes the existence 
 of ether, an extremely tenuous substance, pervading all bodies and extending 
 through the universe; which is the vibratory medium in the transmission of 
 all these forms of energy. This is, of course, a strictly hypothetical cause. 
 Some other hypothesis may, at some future time, take its place. 
 
 5th. The hypothesis is to be preferred which takes into account the 
 complex nature of causes and makes the right ones prominent. 
 
 Almost universally in nature causes are manifold and complex, and none 
 of the complex elements can be overlooked without falling into error. For 
 example, about 1854, some excavators brought up some burnt brick and pot- 
 tery from the depth of 60 and 72 feet, in the valley of the Nile. Assuming 
 that they were found where they were made, and that the alluvium had been 
 deposited upon them at the rate at which the Nile now makes its deposit, and 
 that this was the only cause at work, it was calculated mathematically that the 
 relics must be from 12,000 to 60,000 years old. One causal element omitted 
 was the weight of the brick-bats in connection with the fact (also causal) that 
 all the region is a vast quagmire during the inundation which covers it with 
 water during a large part of the year. Sir Robert Stephenson afterwards 
 found in the Delta near Damietta, at a far greater depth, a brick bearing the 
 stamp of Mohammed Ali (1808). Some one said satirically that the main ques- 
 tion in the first case should have been : How long will it take a brick to sink 
 72 feet in a quagmire? But although this might be the main question, all 
 causes should be given their due weight in reaching the correct result. 
 
TEE FORMATION OF REASONING. 155 
 
 Bale 2d. — See that the hypothesis in each case combines and ex- 
 plains all the facts. This is the fact test. This embraces various 
 particulars. 
 
 1st. The hypothesis must embrace the facts. 
 
 This is the object in forming hypotheses, and forgetfulness of it is fatal to 
 correct thinking. The question in inductive science should not be, what must 
 be ? but, what is ? The old science, putting assumption and deduction in the 
 place of induction from facts, taught that the orbits of the heavenly bodies 
 must be circular, because " the circle is the perfect figure ;" the true science 
 teaches that the orbits of the heavenly bodies are, in fact, ellipses, because this 
 alone agrees with the facts as explained by the laws of centrifugal and cen- 
 tripetal force in connection with gravitation and the motion of the bodies. 
 
 2d. The hypothesis must explain all the facts. A single fact clearly 
 contradictory to any hypothesis calls for the modification or abandon- 
 ment of the hypothesis. 
 
 It is manifest that even a single fact clearly contradictory to any 
 hypothesis proves the hypothesis untenable, as that single fact, though 
 there were no other such fact, would prove the principle embodied in 
 the hypothesis not universal. The place occupied by exceptional facts 
 is thus seen to be very important. As Jevons has said, "they are 
 commonly the points from which we start to explore new regions of 
 knowledge." As all exceptions are not equally fatal to the hypotheses 
 to which they appear to be exceptional, Jevons (Principles of Science, 
 pp. 644-672) has arranged them under eight classes : 
 
 (1.) " Imaginary, or false, exceptions, that is, facts, objects, or events which 
 are not really what they are supposed to be. 
 
 (2.) " Apparent but congruent exceptions, which, though apparently in con- 
 flict with a law of nature, are really in agreement with it. 
 
 (3.) " Singular exceptions, which really agree with a law of nature, but ex- 
 hibit remarkable and unique results of it. 
 
 (4.) " Divergent exceptions, which really proceed from the ordinary action 
 of known processes of nature, but which are excessive in amount or monstrous 
 in character. 
 
 (5.) " Accidental exceptions, arising from the interference of some entirely 
 distinct but known law of nature. This is the largest class of exceptions. 
 
 (6.) " Novel and unexplained exceptions, which lead to the discovery of a 
 new series of laws and phenomena, modifying or disguising the effects of pre- 
 viously known laws, without being inconsistent with them. 
 
 (7.) " Limiting exceptions, showing the falsity of a supposed law in some 
 cases to which it has been extended, but not affecting its truth in other cases. 
 
 (8.) " Contradictory or real exceptions, which lead us to the conclusion that 
 a supposed hypothesis or theory is in opposition to the phenomena of nature, 
 and must therefore be abandoned." These exceptions are the most important 
 of all, " since they lead to the entire rejection of a law or theory before ac- 
 cepted." No law of nature can fail; there are no such things as real excep- 
 tions to real laws. Where contradiction exists, it must be in the mind of the 
 
156 PRACTICAL LOGIC 
 
 experimentalist. Either the law is imaginary or the phenomena which con- 
 flict with it ; if, then, by our senses we satisfy ourselves of the actual occurrence 
 of the phenomena, the law must be rejected as illusory. 
 
 Rule 3d. — Apply the principles of deduction to the hypothesis, as- 
 certaining what ought to happen in any given circumstances if the 
 hypothesis be true, and test the predicted results by observation and 
 experiment. This is the prediction test. 
 
 When any hypothesis embodies a real cause, it gives the thinker the power 
 of predicting by deduction the particular phenomena which come under it. 
 The verification of such predictions is one of the last and highest tests of an 
 induction. "There is no more convincing proof of the soundness of knowl- 
 edge than that it confers the gift of foresight." Astronomy furnished the 
 earliest development of this power. Thales, the Father of Philosophy, pre- 
 dicted the eclipse which suddenly turned day into night during a battle be- 
 tween the Medes and Lydians. The recent discovery of Neptune is the most 
 remarkable instance of this prevision. The method of prediction by deduction 
 is equally applicable to all the physical and mental sciences. 
 
 "As we deduce more and more conclusions from any hypothesis and find 
 them verified by trial, the probability of the theory increases in a rapid man- 
 ner ; but we never escape the risk of error altogether. Absolute certainty is 
 beyond the powers of inductive investigation, and the most plausible supposi- 
 tion may ultimately be proved false. 
 
 " Such is the groundwork of similarity in nature, that two very different 
 conditions may often give closely similar results. We sometimes find our- 
 selves, therefore, in possession of two or more hypotheses which both agree 
 with so many experimental facts as to have great appearance of truth. Under 
 such circumstances we have need of some new experiment, which shall give 
 results agreeing with .one hypothesis but not with the other." This gives rise 
 to what Bacon called an Experimentum Crucis, an " Experiment of the Fin- 
 ger Post." In Pascal's day his own hypothesis, that the mercury rose in the 
 tube because of the pressure of the atmosphere, had as its rival the doctrine, 
 that this phenomenon was due to nature's abhorrence of a vacuum. His ex- 
 periment of causing a barometer to be carried to the top of the Puy-de-D6me 
 was the crucial experiment which established his own theory and negatived 
 the rival hypothesis. 
 
 Eule 4th. — Avoid the common error of assuming unverified hypoth- 
 esis, or such as are based upon other unverified hypotheses, as true, 
 
 The failure to conform to this general rule has been the bane of sci- 
 entific investigation in both its physical and mental spheres in all ages. 
 The spirit of speculation and the determination to believe one's own 
 dreams to be the reality have overborne the spirit of the true philoso- 
 pher. " The philosopher," says Faraday, " should be a man willing 
 to listen to every suggestion, but determined to judge for himself. He 
 should not be biased by appearances ; have no favorite hypothesis ; 
 be of no school ; and in doctrine have no master. He should not be 
 a respecter of persons, but of things. Truth should be his primary 
 
THE FORMATION OF REASONING. 157 
 
 object. If to these qualities be added industry, be may indeed hope 
 to walk within the veil of the temple of nature." 
 
 Topic Second. — Products of Inductive Reasoning. 
 
 The product of induction is a generalization. The pro- 
 cess may be expressed in quasi-syllogistic form, as follows : 
 
 Mars, Jupiter, the Earth move in elliptical orbits round the sun; 
 
 These are (as good as— or fairly represent) all the planets ; 
 .*. All the planets move in elliptical orbits round the sun. 
 
 Or letting M lf M 2 , etc., represent the different instances from which 
 the inductions are made, we have the formula: 
 
 !Mj, as well as M 2 , is P; 
 M lt as well as M 2 , is S ; 
 .-. Every S is P. 
 
 I. Varieties of Induction. 
 
 Inductions are divided by logicians into perfect and im- 
 perfect. 
 
 1. The so-called perfect induction takes place " when, by 
 a perfect enumeration of all individuals or particulars, the 
 whole sphere of the universal is exhausted." For example : 
 
 Mercury revolves on its axis ; so do Venus, the Earth, Mars, Jupiter, 
 and Saturn. But these are all the old planets. .*. All the old planets 
 revolve upon their axes. 
 
 This, however, is enumeration and addition rather than inference. 
 It is ordinarily applicable, of course, only to spheres of objects so 
 limited that all the individuals may be successively examined. 
 
 2. The so-called imperfect induction includes the cases 
 in which the universal is reached by inference, without the 
 complete enumeration of objects. Sometimes only a very 
 few objects out of an indefinite number are examined. 
 
 The conclusion in such cases may be made universal, first, by the 
 pure assumption of a real causal nexus between the subject and pre- 
 dicate of the conclusion, — giving what may be called an inductive 
 guess, often mistaken for induction ; or, secondly, by the strictly 
 inductive method of finding some real, adequate and, if possible, true 
 cause, to connect the subject and predicate of the conclusion, — giving 
 what may be called a true induction. 
 14 
 
158 PRACTICAL LOGIC 
 
 (1.) The inductive guess or primary induction may be illustrated by 
 the following example : 
 
 Iron is heavier than water, so is silver, quicksilver, gold, etc. 
 .*. All the metals are heavier than water. 
 
 The primitive inductions thus formed are mostly false, as in this 
 example, since some of the metals, as sodium and potassium, are lighter 
 than water. A vast amount, not only of the thinking of common 
 life but also of the so-called scientific induction, is of this nature, and, 
 therefore, at the best only the work of the imagination, and at the 
 worst mere crude guess-work. 
 
 (2.) The true induction is that in which a causal nexus, found in 
 the nature or essential relation of the objects examined, is more or 
 less completely established. The generalizations in such cases vary in 
 degree of probability. The highest degree of probability is reached 
 where some true and known cause is at work producing like effects in 
 the various individual instances. The probability decreases as the 
 cause recedes into the region of the unknown and hypothetical. The 
 true induction may be illustrated by the following examples : 
 
 Mercury, Venus, Jupiter, etc., appear to be wanderers among the fixed stars ; 
 
 These represent all the planets (since this apparent wandering is due to the 
 motion of these stars and the earth) ; 
 
 . • . All the planets will probably appear to be wanderers among the fixed 
 stars. * 
 
 3. Analogy has already been shown (p. 136) to involve 
 both induction and deduction, the inductive being the prin- 
 cipal element. As analogy depends upon some assumed 
 likeness, its kinds may be indicated by the kinds of prop- 
 erties (pp. 28-9) in which the likeness is found. That like- 
 ness may be in either essential or non-essential properties. 
 
 (1.) Analogy based npon resemblance in essential properties is the 
 
 most valuable kind. The reasoning in this case rests upon the generic 
 and essential nature of the objects coordinated in the analogy. This 
 may be illustrated by the inference made by Franklin in November, 
 1749, which must be reckoned among inferences from analogy, since 
 lightning and electrical phenomena were not yet known to be the 
 same but only similar : 
 
 " The electric fluid, as it shows itself in experiments made by us, is attracted 
 by projecting metallic points; 
 
THE FORMATION OF REASONING. 159 
 
 " This electric fluid and lightning agree in the properties, that they give light 
 of the same color, have a quick motion, are conducted by metals, etc., etc. ; 
 
 " Hence it is to be presumed that lightning will also be attracted by project- 
 ing metallic points." 
 
 (2.) Analogy based upon resemblance in peculiar or accidental prop- 
 erties is of comparatively little value, since these properties do not 
 indicate any essential or causal principle lying back of them. This 
 may be illustrated by the following examples : 
 
 " The American swan is white ; therefore, the Australian swan is white." 
 " John Smith, a man with a red nose, is a drunkard ; therefore, Timothy 
 Jones, another man with a red nose, is a drunkard." 
 
 But the Australian swan, though in all essential respects the same 
 as the American, differs in the non-essential property of color, being 
 found to be black. In like manner the red nose may be the result of 
 exposure to the sun, or of any other of many causes. 
 
 (3.) Analogy based upon the resemblance of relations is the most 
 difficult to deal with of all the forms of analogy. This is analogy in 
 the strictest sense. It is necessary in all inferences of this kind to 
 consider with great care how far the analogy holds. In the direct 
 form these characteristics of analogy may be illustrated by the rela- 
 tions of a foot to a man and a mountain. It is under the man as a 
 support and under the mountain as a support, but its being that upon 
 which man walks does not warrant the extension of this relation to 
 the foot of a mountain. Analogy from contradictories is illustrated 
 when, from the fact that virtue produces happiness, it is inferred by 
 analogy that its contradictory moral quality, vice, will produce unhap- 
 piness. 
 
 II. Fallacies in Induction. 
 
 The most common fallacies in induction arise from fail- 
 ure, first, in dealing with the facts ; or, secondly, in finding 
 the cause. 
 
 1. The most common fallacy is that of false generalization 
 (fictae universalitatis, or unreal universality). This makes a 
 show, at least, of complete and conclusive induction. 
 
 (1.) This may result from careless and incomplete observation of facts, 
 and may then be called the fallacy of insufficient observation. Thus, 
 a French physician, it is said, once gave a Frenchman, who had 
 typhoid fever, chicken soup ; the patient recovered, and on the basis 
 
160 PRACTICAL LOGIC 
 
 of this one fact the doctor made the generalization, — "Chicken soup 
 will cure a man who has typhoid fever." He afterwards used the 
 same remedy in the case of an Englishman who had the same disease ; 
 the patient died, and the doctor reached and recorded the further gen- 
 eralization, — " Chicken soup cures a Frenchman, but kills an English- 
 man." 
 
 (2.) The false generalization may also result from the hasty assump- 
 tion of something as the cause which is not the cause (non causa pro 
 causa). That which is assumed as the cause in such cases may be 
 either a simple concomitant or a mere antecedent (post hoc ergo propter 
 hoc). The fallacy of assuming that a simple concomitant is a cause 
 (causa hoc ergo propter hoc) is illustrated by the conclusion of the 
 materialist, that since chemical action in the brain accompanies mental 
 action, it is the cause of mental action ; which is paralleled by the 
 assumption, that because the small boy's boots always accompany the 
 small boy, therefore, they are the small boy. The fallacy of assuming 
 that a mere antecedent is a cause (post hoc ergo propter hoc) is illus- 
 trated by the inference, among the ancient Romans, that when a 
 general engaged the enemy where the response of the augurs had been 
 unfavorable, and suffered defeat, the cause of the disaster was the 
 unfavorable character of the auspices. 
 
 Praxis. — Test the following conclusions reached by induction ; state 
 whether the induction is valid or not in each case ; verify the induction 
 when valid, and when not valid show what is the fallacy involved : 
 
 1. " The Jews are rogues,— The Carthaginians, faithless,— The Cretans, liars, 
 — The French, braggadocios,— The Germans, mystics, — The rich, purse-proud, — 
 The noble, haughty,— Women, frivolous,— The learned, pedants." 2. Matter 
 is eternal. 3. Spirit is essentially immortal. 4. The Irish are malcontents. 5. 
 All human languages had a common origin. 6. The great civilizations have 
 all flourished in the North Temperate Zone. 7. Man is what circumstances 
 make him. 8. u There 's a divinity that shapes our ends, rough hew them how 
 we will." 9. That which survives is fittest. 10. All the planets revolve on 
 their axes. 11. Conceited men are always shallow. 12. Ignorant men are con- 
 ceited. 13. Selfish men are not men of principle. 14. Man is born sinful. 15. 
 The Christian nations are the progressive nations. 16. The Protestant nations 
 are the foremost nations in the world. 17. The reach of gravitation is univer- 
 sal. 18. The best education is secured by means of the Classics. 19. The best 
 education is secured by means of the Natural Sciences. 20. The best edu- 
 cation is secured by means of the combined study of the Classics, Natural 
 Sciences, and Mathematics. 21. The appearance of a comet is the harbinger 
 of famine, pestilence, and war. 22. Friday is an unlucky day. 
 
 State, in the following cases, whether the facts are exceptional, and, 
 if so, to what class each belongs ; and show whether and how they 
 
THE FORMATION OF REASONING. 161 
 
 can be reconciled with the hypotheses to which they appear to be ex- 
 ceptional : 
 
 1. The rotation of the earth upon its axis gives to all the stars an apparent 
 motion of rotation from east to west. The Pole Star seems not so to revolve. 
 2. According to the Newtonian view of gravitation all bodies are heavy. But 
 name, bubbles, clouds, etc., ascend, and were, therefore, regarded by the an- 
 cients as essentially light. 3. The Copernican theory teaches that the earth in 
 revolving moves toward the east at the rate of a thousand miles or more an 
 hour. It has been objected to it that, if this be so, then a stone dropped from 
 the topmast of a ship at anchor ought to fall behind toward the west, just as a 
 stone dropped from the mast-head of a moving ship would fall behind, owing 
 to the motion of the ship. 4. The ancients held that the general tendency of 
 bodies on the earth is downward. In the case of the loadstone held over iron, 
 the iron had a tendency upward. This could not be explained by the hypoth- 
 esis of essential lightness, since iron is one of the heaviest substances. 5. 
 According to the theory of Torricelli and Pascal, the mercury ought to stand 
 at a height of about 31 inches in the barometer. Boyle showed that in a 
 perfectly cleansed tube it could be made to stand as high as 75 inches. 6. 
 According to the hypothesis of the materialistic evolutionist, the development 
 of the universe has been a continuous change and progress from the primor- 
 dial atom, without break or interference of any other than material forces. 
 Dr. McCosh, in Christianity and Positivism (Appendix, p. 344), enumerates 
 eleven breaks in the continuity, among which are the following : M Chemical 
 action cannot be produced by mechanical power." " Life, even its lowest 
 forms, cannot be produced from unorganized matter." " Protoplasm can be 
 produced only by living matter." "A living being can be produced only from 
 a seed or germ." "An animal cannot be produced from a plant." "Sensation 
 cannot be produced by insentient matter." The genesis of a new species of 
 plant or animal has never come under the cognizance of man, either directly 
 or indirectly. Consciousness cannot be produced out of mere matter or sensa- 
 tion. " We have no knowledge of man being generated out of the lower ani- 
 mals." "All human beings, even savages, are capable of forming certain high 
 ideas, such as those of God and duty ;" the brute is not. 
 
 State and test the following hypotheses : 
 
 1. The Wolffian hypothesis of the origin of the Homeric Poems. 2. The 
 hypotheses concerning the origin of the Four Gospels. 3. The hypotheses 
 concerning the nature of Electricity. 4. The hypotheses concerning the 
 nature of Heat. 5. The hypotheses concerning the composition of Comets. 
 6. The hypotheses concerning the origin of Life on our globe. 7. The hypoth- 
 eses concerning the nature of Man. 8. The hypotheses concerning the nature 
 of Beauty. 9. The hypotheses concerning the origin of the Universe. 
 
 Note.— For a complete and extended treatment of Induction, the teacher 
 and student are referred to the following works : Jevon's Principles of Science; 
 Mill's System of Logic, Eatiocinative and Inductive. 
 14* L 
 
162 PRACTICAL LOGIC. 
 
 CHAPTER II. 
 
 THE UNFOLDING OP REASONING OR THE 
 SYLLOGISM. 
 
 The treatment of the formation of reasoning is naturally 
 followed by the consideration of the unfolding and testing 
 of its various kinds, as embodied in the Syllogism, and the 
 presentation of the various forms of Fallacy or unsound 
 reasoning. 
 
 Practical Logic should train the thinker to distinguish 
 readily between a true syllogism and one that only seems 
 to be a true one. This requires the treatment, in successive 
 Sections, of the Forms and Tests of Categorical and Hypo- 
 thetical Syllogisms, and the kinds of Fallacies. 
 
 Section I.— The Categorical Syllogism Unfolded. 
 In unfolding the categorical syllogism, the nature and 
 kinds of which have already been presented (p. 141), the 
 following Topics will be considered : 
 
 Topic I. — The Possible Forms of the Syllogism, or Figure and Mood. 
 Topic II.— The Testing of the Valid Forms. 
 Topio III.— Complex and Abnormal Forms. 
 
 Topic First. — The Possible Forms of the Simple Categor- 
 ical Syllogism. 
 
 The possible forms of the single syllogism are determined 
 by the various positions of the middle term, in the premises, 
 with reference to the major and minor terms, and the pos- 
 sible combinations of the four normal judgments, A, E, I, 
 0, in groups of three. The first gives rise to Figure, the 
 second to Mood. 
 
 I. Figure of Syllogisms. 
 
 Syllogisms are divided into different Figures by the posi- 
 
THE UNFOLDING OF REASONING. 163 
 
 tion of the middle term. The possible positions are four, 
 
 which give rise to as many Figures : 
 
 Figure I, middle term subj. of maj. prem. and pred. of minor. 
 Figure II, u pred. of both maj. and min. premises. 
 
 Figure III, ■■ " subj. " " " " " 
 
 Figure IV, " " pred. of maj. prem. and subj. of minor. 
 This may be expressed and illustrated as follows : 
 
 Every virtue is praiseworthy ; = A 
 
 Eloquence is a virtue; = A 
 
 . Eloquence is praiseworthy. = A 
 
 No vice is praiseworthy ; — E 
 
 Eloquence is praiseworthy; =A 
 
 Fig. I. 
 
 sub prae. 
 
 Fig. II. 
 
 * -^ ' l/.S **\ P .*. Eloquence is not a vice. =E 
 
 sub sub. 
 
 Fig. IV. 
 
 P Every virtue is praiseworthy ; = A 
 
 ^' ^ " -J M »— S Every virtue is useful ; = A 
 
 P .•. Something useful is praiseworthy. = I 
 
 M Every virtue is praiseworthy ; = A 
 
 S Everything praiseivorthy is useful ; = A 
 
 ■^ l.'.S »— P .'. Something useful is a virtue. =1 
 
 In these examples the mnemonic sub and prae stand for subject and 
 predicate. The wedge-shaped figure or line (^- ) denotes a judg- 
 ment. Its thick end turns toward the subject of extension, which is 
 contained as a species under the predicate as a genus. The perpendic- 
 ular stroke drawn through the line (bJ- — ) indicates negation. In 
 the Hamiltonian Notation, of which this is a part, the heavy horizon- 
 tal line (mamamm) used in the unfigured syllogism (p. 165 j, indicates 
 equality between subject and predicate, or a substitutive judgment. 
 
 Note. — The syllogisms ordinarily used in the examples in Logic are made 
 up of propositions of extent, and are, therefore, called extensive syllogisms. 
 Hamilton introduces and insists upon the intensive syllogism. This is ex- 
 pressed by reversing the wedge-shaped figure, which in this case represents 
 the copula as meaning "comprehends," instead of "is contained under," 
 which is its meaning in the extensive syllogism. The two forms may be illus- 
 trated : 
 
 The notion responsible is contained under the notion free- 
 agent; Km P 
 The notion man is contained under the notion responsible 
 agent ; S m m M 
 W .*. The notion man is contained under the notion free- 
 agent. .'. S Bm- P 
 
164 PRACTICAL LOGIC. 
 
 The notion man comprehends the notion responsible ; 
 The notion responsible comprehends the notion free ; 
 .*. The notion man comprehends the notion free. 
 
 In the first form the notions are class notions; in the second, concepts proper. 
 In the second form the premises of the first form are transposed. With this slight 
 change extensive and intensive syllogisms conform to the same rules, and are 
 so nearly identical that the intensive form does not need separate treatment. 
 In fact, both propositions of extent and of content are often used in the same 
 syllogism. Thus: 
 
 All of the metals are positive ; Proposition of content. 
 
 Silver is one of the metals ; Proposition of extent. 
 
 .-. Silver is positive. Proposition of content. 
 
 II. Mood of Syllogisms. 
 
 The Mood of a Syllogism is the arrangement of its prop- 
 ositions according to their respective quantity and quality. 
 There are as many possible Moods as there are combinations 
 of the four normal propositions, A, E, I, 0, in syllogistic 
 form. 
 
 It will be seen on examination that in the premises each of the four 
 may be placed first, and then followed by each of the four successively, 
 giving 4 X ^ = 16 combinations. Each of these 16 combinations may 
 
 then be followed successively in the 
 conclusion by each of the four judg- 
 ments, A, E, I, 0, giving 16X4 = 64 
 possible syllogistic combinations. These 
 forms will be presented later, in gath- 
 ering up the results of the application 
 of the Rules, and need not, therefore, be here given. The student, 
 moreover, will be able readily to form the combinations for himself. 
 
 It will be found, when the proper tests are applied, that compar- 
 atively few of these combinations give valid syllogisms. 
 
 Topic Second. — The Testing of the Valid Forms. 
 
 Two methods have been employed in testing the validity 
 of the various combinations : 
 
 First, By what Hamilton calls " the thorough-going quan- 
 tification of the predicate." 
 
 Second, By comparing the spheres of the notions in the 
 
 AA 
 
 E A 
 
 I A 
 
 OA 
 
 AE 
 
 EE 
 
 IE 
 
 OE 
 
 A I 
 
 E I 
 
 I I 
 
 I 
 
 AO 
 
 EO 
 
 10 
 
 00 
 
THE UNFOLDING OF REASONING. 165 
 
 various combinations and framing and using Rules based 
 upon the results. This is the logical method. 
 
 ist. The Unfigured Syllogism.— By quantifying the predicate, Hamilton 
 has sought to dispense with Figure altogether. By the explicit quantification 
 of the terms the exact quantity of each is brought out. After the quantifica- 
 tion the relation between the terms of the judgments may, according to Ham- 
 ilton, be expressed by the sign of equality, and the subject and predicate may 
 indifferently change places. The figured and unfigured form may be illustrated 
 by example : 
 
 Figured. —Fig. I. Unfigured. 
 
 A Men are rational ; All men = some rational ; 
 
 A Negroes are men ; All negroes = some men ; 
 
 A .*. Negroes are rational. .*. All negroes = some rational. 
 
 If the object in introducing this new method is to simplify reasoning it is 
 not attained, since while it apparently simplifies it really complicates it. The 
 fatal objection to its general introduction is found in the fact, that the instant 
 the predicate of a judgment is quantified, it ceases to be a logical or qualitative 
 whole and becomes a simple quantitative or mathematical whole. The judgment 
 is no longer a logical, but a simple mathematical, judgment. Davis enforces this 
 position in M The Theory of Thought," p. 124: 
 
 " For, consider the meaning of ' aU ' in the predicate. It is not, it cannot be, 
 the distributive, divisive, exemplar * all,' but is always the total, indivisible, 
 cumular ' all/ a mathematical whole. E. g., 'AU men are bimana ;' this is 
 the distributive ' all,' meaning that all, each, and every man is in the class, or 
 has the mark, bimana. But let us say 'All men are all bimana ;' this does not 
 mean ' Every man is aU bimana,' nor 'All men are every bimana,' nor ' Every 
 man is every bimana,' which is nonsense. It means 'All men (as a mathemat- 
 ical, total, collective whole) are all bimana' fas ditto). Thus ' aU' in the pred- 
 icate is never distributive, but cumular, and enforces the ' all ' of the subject 
 also to be cumular. So also the total predicate of a negative is a mathemat- 
 ical, not a distributed total ; and ' some ' in the predicate is a mathematical 
 part. More generally, whenever the quantity of the predicate is designated, 
 both terms are individuals, and the judgment is mathematical." 
 
 The decision whether a given combination leads to a valid inference, and 
 the proof of the validity or non-validity, must depend upon the comparison 
 of the spheres of the notions as given in the premises of the apparent syllo- 
 gism. The reciprocal relations of notions, already presented (pp. 40 and 45), 
 comprehend all the relations essential in the comparison of notions in reason- 
 ing. These relations, as has been seen, may be made apparent to the senses 
 by the use of geometrical figures. 
 
 2d. The proper method of testing the validity of the 
 various combinations of judgments as premises is by com- 
 paring the spheres of the notions involved in these judg- 
 ments. The valid forms are determined by General Princi- 
 ples arising out of the Logical Axioms ; by General Rules 
 
166 PRACTICAL LOGIC 
 
 arising out of the relations of the terms and propositions 
 of the Syllogism ; and by Special Canons arising out of the 
 nature of the particular Figures. Figure I. has always been 
 considered the normal form of the syllogism, to which the 
 other forms may be reduced. Hence, the principles which 
 govern the Reduction of Syllogisms to this Figure need to 
 be presented. For convenience of reference, a Conspectus 
 of Results will also be given. 
 
 I. The General Principles. 
 
 At the foundation and applying equally to all the figures 
 are three general principles embodying the axiom of Iden- 
 tity or Affirmation and of Contradiction or Negation. 
 
 First General Principle. Affirmative Conclusion. — If, when the 
 major and minor terms are compared with the same middle term, they 
 both agree with it, they may agree with each other. This is the basis 
 of affirmative conclusions. 
 
 Second General Principle. Negative Conclusion. — If, on such com- 
 parison, one term agrees and the other disagrees with the same middle 
 term, they disagree with each other. This is the basis of negative 
 conclusions, which, -therefore, result from the combination of one af- 
 firmative and one negative premise. 
 
 Third General Principle. No Conclusion. — If, on such comparison, 
 both terms disagree with the same middle term, it is uncertain whether 
 they agree or disagree with each other, and, therefore, no valid infer- 
 ence can be drawn in such cases. This is the case where both prem- 
 ises are negative. 
 
 II. The General Rules. 
 
 The general rules arising out of these general principles 
 depend upon the relations of the terms and propositions of 
 the syllogism. They may be reduced to seven, and are 
 equally applicable to all the figures. 
 
 Rule 1st. — There must be three, and only three, terms in any valid 
 syllogism. The major and minor terms would not otherwise be logi- 
 cally connected at all. This needs no illustration. It guards against 
 the common Fallacy of Four Terms, which oftenest arises from the use 
 
TEE UNFOLDING OF REASONING. 167 
 
 of equivocal terms (p. 82) or want of clear thought. In all cases the 
 middle term needs to be carefully examined in order to make sure that 
 it is used in precisely the same sense in both premises. Whenever it 
 is not so used the case is one of substantially four terms. E. g. : 
 11 What we eat grows in the fields or is the flesh of animals ; 
 
 Cooked food is what we eat ; 
 .*. Cooked food grows in the fields or is the flesh of animals." 
 
 This is a case of two middle terms. In one premise, " what we eat" 
 is used with reference to its mere essence; in the other, with reference 
 to the accident or property of being cooked. This is the Fallacy of 
 Accident (Fallacia Accid-entis). 
 
 Rule 2d. — Tlie middle term must be distributed at least once. The 
 necessity for this arises from the fact that without it the major and 
 minor terms might be compared with different parts of the sphere of 
 the middle term, and so fail of being brought into logical connection. 
 
 E,g ' : ] /^?\ 2 /r^ 3 - 
 
 All poets (P) are men (M) ; == A fa W\ L&. 
 
 All orators (S) are men (M). = A \(J^ 
 
 We cannot infer that " All poets are orators," or that "Some poets 
 are orators," since the universal affirmative, A, does not distribute the 
 predicate (p. 115), which is here the middle term. Such conclusions 
 would result in the Fallacy of Undistributed Middle. 
 
 Rule 3d. — A term undistributed in the premises must not be dis- 
 tributed in the conclusion. Otherwise the conclusion would include 
 more than is involved in the premises. The violation of this rule is 
 called the Fallacy of Illicit Process. The fallacy may occur either 
 with the major term or with the minor. 
 
 Illicit Process of the Major Term. 
 
 All birds (M) are winged (P) ; = A /T^\ 
 
 A bat (S) is not a bird (M) ; = E (S) /^/p ^ 
 
 .*. A bat (S) is not winged (P). = E ^V® 
 
 The major term, "winged," is undistributed in the major premise 
 (A), and distributed in the conclusion (E). Hence the inference is not 
 valid, as may be seen from the above presentation of the relation of 
 the spheres of the notions. 
 
 Illicit Process of the Minor Term. 
 
 Persons without imagination (M) are not true poets (P) ; = E 
 
 Good logicians often (S) are without imagination (M) ; = I 
 
 .*. Good logicians (S) are not true poets (P). = E 
 
168 PRACTICAL LOGIC. 
 
 In this case the word " often" makes the judgment equivalent to, 
 " Some good logicians are not true poets ;" while the universal neg. 
 ative conclusion denies of "all good logicians" that they are "true 
 poets." 
 
 Rule 4th. — The conclusion must always follow the weaker part. 
 By this is meant that, if one premise is negative the conclusion must 
 be negative, and, if one premise is particular the conclusion must be 
 particular. This does not need illustration. 
 
 It follows that universal conclusions can be reached only from uni- 
 versal premises. It will appear subsequently that universal conclu- 
 sions are not warranted in all cases by universal premises, since they 
 would often involve the fallacies of undistributed middle or of illicit 
 process. 
 
 Rule 5th. — No valid inference can be drawn where both premises 
 are negative. This follows from the Third General Principle. The 
 relation of the major and minor terms to each other is left wholly un- 
 determined by the form of the judgment. 
 
 Three cases come under this Rule : where both premises are universal neg- 
 ative: where one is universal negative and the other particular negative; 
 where both are particular negatives. The Rule, therefore, excludes, as invalid 
 in all instances, four of the sixteen possible combinations,— E E,EO,OE,0 0,— 
 leaving only twelve possibly valid combinations. 
 
 A single illustration, coming under the first case, will suffice to assist the 
 student in presenting for himself in diagram the various forms which the in- 
 determinate relations of the major and minor terms may take. 
 No poets (P) are angels (M) ; No P is M ; = E 
 No men (S) are angels (M) ; No S is M ; = E 
 
 By the terms of the judgments both " poets " and " men " are excluded from 
 " angels," but they may stand to each other in any one of at least the five fol- 
 lowing relations (p. 40): 1st. They may be independent or coordinate. 2d. 
 They may be coextensive. 3d. S may include P. 4th. P may include S. 5th. 
 S and P may intersect each other. 
 
 s p i V y \*s Ky<^- W s v.s j 
 
 It will be found that, in the second and third cases of negative premises, the 
 possible relations of the terms become even more complicated. 
 
 Rule 6th. — No valid inference can be drawn where both premises 
 are particular. In such instances the precise connection of the spheres 
 of the major and minor terms with that of the middle cannot be deter- 
 mined from the form of the judgments. 
 
THE UNFOLDING OF REASONING. 169 
 
 Three cases come under the Rule : where both premises are particular affir- 
 mative ; where one is particular affirmative and the other particular negative ; 
 where both are particular negative. 
 The first case, 1 1, will furnish a sufficient illustration. 
 
 Some poets (M) are intellectual (P) ; Some M is P ; =1 
 Some poets (M) are emotional (S) ; Some M are S ; = I 
 
 In this case the " intellectual" and " emotional " poets might stand in either 
 of the following relations: 1st. They might exactly coincide. 2d. They might 
 wholly exclude each other. 3d. They might intersect each other, etc. 
 
 U-\ 2^r\ 3 
 
 ( p X l \ 
 
 etc. 
 
 The same indeterminateness, in the relation of the major and minor terms 
 to each other through the middle term, may be shown to exist in the other 
 cases. The third case is likewise excluded from valid syllogistic forms by the 
 Rule for negative premises. 
 
 The Rule, therefore, excludes three combinations not excluded by the pre- 
 vious Rule : 1 1, 1 O, O I ; leaving but nine possibly valid combinations. 
 
 Apparent Exceptions. — Two apparent exceptions to this Rule need 
 to be noted: first, syllogisms involving plurative judgments (p. 114); 
 secondly, those in which one or both of the premises are substitutive 
 judgments (p. 113). These are not, of course, strictly particular 
 judgments. 
 
 Plurative Judgments, whether indefinite or numerically definite, give 
 valid conclusions, as seen in the following examples : 
 
 Most men (M) are conceited (P) ; A — Ignora11 *- L J) 
 
 Conceited. 
 Most men (M) are ignorant (S) ; jr Ignorant and conceited. 1 
 
 ,\ At least some conceited men (S) are ignorant (P). 
 
 It is obvious in this case that " most men " in the major premise may coin- 
 cide more or less fully with "most men" in the minor, as illustrated in the 
 diagrams. In the first case, the line A C represents the " ignorant," B D the 
 " conceited," and A D " all men." The line B C represents the minimum of 
 agreement, in the given case, when the " ignorant" and " conceited" differ to 
 the utmost. In the second case, E F represents both the "ignorant" and the 
 " conceited," and EG" all men." The line E F represents the maximum of 
 agreement, when the "ignorant" and "conceited" agree to the utmost, i. e., 
 coincide. 
 
 If this be given the numerically definite or proportional form, it may becomes 
 
 80 out of every 100 men are conceited ; 
 
 80 out of every 100 men are ignorant ; 
 /. At least 60 out of every 100 conceited men are ignorant 
 15 
 
170 PRACTICAL LOGIC. 
 
 In this instance the " 80" of the major premise may agree more or less fully 
 with the " 80 " of the minor, as illustrated by the diagram. The minimum of 
 agreement, as shown in the following diagram, is D B, or 60 out of every 100 ; 
 the maximum, E F, 80 out of every 100. 
 
 Ignorant = 80 B Ignorant-conceited = 80 
 
 1 I I I 1 1 I 1 1 1 I I I I 1 I 1 I 1 1 I I 
 
 A D | Conceited = 80 C E | F G 
 
 Substitutive Judgments, even when particular (Y), often result in 
 making conclusions valid that would be invalid if the premises were 
 mere particular attributives. Such judgments, whether universal or 
 particular, always distribute the predicate (p. 115). They are not, how- 
 ever, strictly particular judgments. For example : 
 
 Some trees (P) are (all the) oaks (M) ; = Y Some P is all M ; 
 Some oaks (M) are white oaks (S) ; =1 Some M is all S •, 
 .*. Some white oaks (S) are trees (P). = I .-. Some S is P. 
 
 Rule 7th. — No valid inference can be drawn from the combination 
 of a particular major premise with a negative minor premise. This 
 will appear from the comparison of the spheres of the notions in the 
 four possible cases : IE; O E ; IO; OO. 
 
 The Rule may be sufficiently illustrated by the first case, I E. The other 
 combinations have also been already excluded from the valid combinations,— 
 O E and O O by negative premises ; I O and O O by particular premises. 
 
 Some iron ores (P) are magnetic (M) ; = I 
 No lead ores (S) are magnetic (M) ; = E 
 
 It is not determined whether the sphere of S is quite separated from the sphere 
 of P, or intersects it, or falls wholly within it. If the attempt were made to 
 draw the conclusion, " No lead ores are iron ores," the negative would dis- 
 tribute the predicate, "iron ores" (P), which is not distributed in the major 
 premise, and would thus result in illicit process of the major term. 
 
 This Rule, therefore, excludes the combination I E, and leaves only eight out 
 of sixteen, which can be valid in any case. These may be stated (numbered 
 for convenient reference in treating the four Figures) as follows : 
 1. A A. 2. E A. 3. I A. 4. O A. Only part of the remaining eight will 
 
 5. A E. be found to hold true in any one of the 
 
 6. A I. 7. E I. Figures. 
 8. AO. 
 
 III. Special Canons of the Figures. 
 
 Each of the four Figures has its special rules resulting 
 from the relations of the terms, which may be embodied in 
 a Canon for that Figure. 
 
 1. Figure I. is that which has the middle term as the sub- 
 
THE UNFOLDING OF REASONING. 171 
 
 ject of the major premise and the predicate of the minor. 
 There follows, from the resulting relations of the terms, — 
 
 Canon 1st. — In Figure I. the requirements are : 
 (Major prem. universal to avoid fallacy of undistributed middle; 
 ( Minor prem. affirmative to avoid fallacy of illicit process of maj. term. 
 
 Testing by this Canon the eight possible combinations left by the 
 General Rales, only six syllogistic forms are found valid in Figure 
 L: AAA, AAI, EAE, EAO, All, EIO. These are reducible to four, 
 since AAI and EAO are but cases of particular or weakened conclu- 
 sions, included in the universals, AAA and EAE. 
 
 Note.— In this Figure the process of testing by the General Rules and the 
 Canon will be applied to the eight combinations successively, in order to pre- 
 pare the student to apply the like process to the remaining three Figures. 
 
 No. i, A A, by the successive addition of the four propositions, A, E, I, O, 
 gives AAA, AAE, AAI, AAO. The second and fourth of these forms, AAE, 
 AAO, drop out since the affirmative premises indicate agreement, while the 
 negative conclusion would infer disagreement. The third, AAI, is included 
 in AAA. Only one valuable form, AAA, remains. It conforms to the Canon, 
 since its major premise is universal and its minor premise affirmative, and the 
 syllogism thus guarded against fallacy. This valid mood is known among 
 logicians by the mnemonic word, Barbara, the meaning of the consonants in 
 which will be subsequently explained under Reduction. It is illustrated in 
 the following example : 
 
 2 All that is composite is dissoluble ; = A All M is P ; 
 .o All material things are composite ; = A All S is M ; 
 «j .*. All material things are dissoluble. = A .-. All S is P. 
 
 No. 2, E A, by the successive addition of the four propositions, A, E, I, O, 
 gives EAA, EAE, EAI, EAO. The first and third of these forms, EAA and 
 EAI, drop out, since the one negative premise always requires a negative con- 
 clusion by Rule 4th. The fourth, EAO, is included in EAE, drawing a partic- 
 ular conclusion when the universal is permissible. The valid mood, EAE, is 
 known among logicians by the mnemonic word, Celarent. It stands the test 
 of the Canon. It is illustrated in the following example : 
 
 a No finite being is exempt from error ; = E No M is P ; /^P\C!*/ 
 
 •g All men are finite beings ; = A All S is M ; 
 
 *5 .\ No man is exempt from error. = E .*. No S is P. 
 
 o 
 
 No. 3, 1 A, gives IAA, IAE, IAI, IAO, none of which are valid, since, besides 
 the breach of the General Rules, the particular major premise, I, violates the 
 Oanon, and always results in undistributed middle. 
 
 No. 4. I O, gives IOA, IOE, IOI, IOO, none of which are valid for the reasons 
 £iven under No. 3. Rule 6th is also violated. 
 
 No. 5, A E, gives AEA, AEE, AEI, AEO, none of which are valid, since the 
 negative minor premise, E, violates the Canon, and results in illicit process of 
 the major term. 
 
 W 
 
172 PRACTICAL LOGIC. 
 
 No. 6, A I, gives AIA, AIE, All, AIO. The first form, AIA, violates Rule 
 4th ; the second and fourth, AIE and AIO, violate the General Principle of all 
 affirmatives. The fourth, All, is valid, standing the test of the Canon. The 
 valid mood is known among logicians by the mnemonic word, Darii. It is 
 illustrated as follows : 
 
 /p 
 .^ All virtues-are laudable ; = A All M is P ; 
 
 £ Some habits are virtues ; = I Some S is M ; 
 Q .*. Some habits are laudable. = I .'. Some S is P. 
 
 No. 7, E I, gives EIA, EIE, EII, EIO. The first, second, and third forms, EIA, 
 E1E, EII, violate Rule 4th. The fourth, EIO, is valid, standing the test of the 
 Canon. The valid mood is known among logicians by the mnemonic word, 
 Ferio. It is illustrated as follows : 
 
 ^ No virtue is reprehensible ; = E No M is P ; 
 
 *g Some habits are virtues ; = I Some S is M ; 
 
 fa .*. Some habits are not reprehensible. = O .*. Some S is not P. 
 
 No. 8, A O, gives AOA, AOE, AOI, AOO, none of which are valid, since The 
 negative minor premise, O, violates the Canon. 
 
 The valid moods in Figure I. are Barbara, Celarent, Darii, Ferio. 
 
 The Figure is naturally and unconsciously used, according to Lambert, 
 to prove qualities. It follows from the " Dictum de omni et nullo" 
 
 2. Figure II. is that which has the middle term as the 
 predicate of both premises. There follows, from the result- 
 ing relations of the terms, — 
 
 Canon 2d. — In Figure II. the requirements are : 
 ( Major prem. universal, to avoid illicit process of maj. term; 
 1 One prem. negative, to avoid undistributed middle. 
 
 Testing by this Canon the eight possible combinations left by the 
 General Rules, only six syllogistic forms are found valid in Figure 
 II. : EAE, E AO, AEE, AEO, EIO, AOO. These are reducible to four, 
 since EAO and AEO are but cases of particular conclusions, included 
 in the universals, EAE and AEE. 
 
 Leaving the student to test the various possible forms, it will be suf- 
 ficient to illustrate the valid moods by examples. The moods are 
 known among logicians as Cesare, Camestres, Festino, Baroko. 
 
 £ Nothing material has free will ; = E No P is M ; 
 g All spirits have free will ; = A All S is M ; 
 
 ° .*. No spirit is material. = E .*. No S is P. 
 
 Cesare is a valid mood, as is seen by its conforming to the Canon, in its uni- 
 versal negative major premise, E. 
 
THE UNFOLDING OF REASONING. 173 
 
 ■£ All colors are visible ; = A All P is M ; 
 c No sound is visible ; = E No S is M ; 
 <« .*. No sound is a color. = E No S is P. 
 
 « 
 
 Camestres is a valid mood, since it conforms to the Canon in its universal 
 major premise, A, and negative minor, E. /— ^ 
 
 ° (G 
 
 .5 No vice is praiseworthy ; = E No P is M ; \C^X *\ 
 
 g Some actions are praiseworthy ; = I Some S is M ; I Q f ) | 
 
 fa .*. Some actions are not vices. = O .'. Some S is not P. ^— Y M J 
 
 Festino is a valid mood, since it conforms to the Canon in its universal neg- 
 ative major premise, E. 
 
 •| All birds are oviparous ; = A All P is M ; I v— / i^ 
 
 •3 Some animals are not oviparous ; = O Some S is not M 
 B .'. Some animals are not birds. = O .*. Some S is not P. 
 
 Baroko is a valid mood, since it conforms to the Canon in its universal major 
 premise and negative minor. 
 
 Figure II is naturally and unconsciously used, according to Lambert, 
 to prove differences. It follows from a " Dictum de diverso :" "Things 
 which are different do not belong to each other." 
 
 3. Figure III. is that which has the middle term as the 
 subj ect of both premises. There follows, from the resulting 
 relations of the terms, — 
 
 Canon 3d. — In Figure III. the requirements are : 
 
 {Minor prem. affirmative to avoid illicit process of maj. term; 
 Conclusion particular to avoid illicit process of min. term. 
 
 Testing by this Canon the eight combinations of premises, six are 
 found to be valid in this Figure: AAI, IAI, All, EAO, OAO, 
 EIO. These are known among logicians as Darapti, Disamis, 
 
 Datisi, Felapton, Bokardo Dokamok , Ferison. 
 
 o. All gilding is metallic ; = A All M is P ; 
 
 2 All gilding shines ; = A All M is S ; 
 
 Q .*. Some things that shine are metallic. = I .*. Some S is P. 
 
 M 
 
 Darapti is a valid mood, since it conforms to the Canon, in its affirmative 
 minor premise, A, and its particular conclusion, I. 
 
 .2 
 
 g Some acts of homicide are laudable ; = I Some M is P ; 
 
 S All acts of homicide are cruel ; = A All M is S ; 
 
 Q .*. Some cruel acts are laudable. = I .*. Some S is P. 
 
 " 15* 
 
174 PRACTICAL LOGIC 
 
 Disamis is a valid mood, since it conforms to the Canon, in its affirmative 
 minor premise, A, and its particular conclusion, I. 
 
 3 All acts of homicide are cruel ; = A All M is P ; 
 
 « Some acts of homicide are laudable ; = I Some M is S ; 
 m .'. Some laudable acts are cruel. = I .*. Some S is P. 
 
 CO 
 
 Datisi is a valid mood, since it conforms to the Canon, in its affirmative 
 minor, I, and its particular conclusion, I. 
 
 c 
 o 
 
 £ No material substance is a moral subject ; = E No M is P ; 
 
 iS All natural substance is extended ; = A All M is S ; 
 
 tn .*. Something extended is not a moral subject. = O .'. Some S is not P. 
 
 Felapton is a valid mood, since it conforms to the Canon, in its affirmative 
 minor premise, A, and its particular conclusion, O. 
 
 d /^S~" 
 
 *H Some syllogisms are not regular ; = Some M is not P ; 
 
 m All syllogisms are things important ; = A All M is S ; 
 PQ .*. Some important things are not regular. = O .*. Some S is not P. 
 io 
 
 Bokardo is a valid mood, since it conforms to the Canon, in its affirmative 
 minor premise, A, and its particular conclusion, O. 
 
 M / 
 
 No truth is without result ; = E No M is P : VvC^ S 
 
 •g Some truths are misunderstood ; = I Some M is S ; 
 
 £ .*. Some things misunderstood are 
 
 not without result. = .'. Some S is not P. 
 
 io 
 
 Ferison is a valid mood, since it conforms to the Canon, in its affirmative 
 
 minor premise, I, and its particular conclusion, O. 
 
 Figure III. is naturally and unconsciously used, according to Lam- 
 bert, to prove examples and conceptions (concepts proper). He founds 
 it on a " Dictum de exemplo :" " When one finds things A which are B, 
 then there are A which are B." 
 
 4. Figure IV. is that which has the middle term as the 
 predicate of the major premise and the conclusion of the 
 minor. There follows, from the resulting relations of the 
 terms, — 
 
 Canon 4th. — In Figure IV. the requirements are : 
 
 If either prem. neg., maj. prem. universal to avoid undistrib. mid. ; 
 If maj. prem. affirm., min. prem. universal to avoid undistrib. mid. ; 
 If min. prem. affirm., conclusion particular to avoid illicit minor. 
 
 Testing by this Canon the eight combinations of premises, five are found to 
 be valid in this Figure : AAI, AEE, IAI, EAO, EIO. These are known among 
 logicians as Braroantip, Camenes, Dimaris, Fesapo, Fresison. 
 
THE UNFOLDING OF REASONING. 
 
 175 
 
 All greyhounds are dogs ; 
 All dogs are quadrupeds ; 
 
 = A 
 = A 
 
 .'. Some quadrupeds are greyhounds. = I 
 
 AllPisM; 
 AUMisS; 
 
 . Some S is P. 
 
 Bramantip is a valid mood, since it conforms to the Canon, in its universal 
 minor premise, A, with particular conclusion, I. 
 
 5 
 u 
 
 All ruminating animals have four 
 
 stomachs ; = A All P is M ; 
 
 No animal with four stomachs is 
 
 carnivorous ; =E NoMisS; 
 
 . No carnivorous animal ruminates. = E /. No S is P. 
 
 Camenes is a valid mood, since it conforms to the Canon, in its universal 
 major premise, A, and its universal minor premise, E. 
 
 Some practically virtuous men are 
 
 necessarians ; = I Some P is If ; 
 
 •§ All necessarians speculatively sub- 
 2 vert the distinction of vice and 
 
 g virtue; =A AllMisS; 
 
 .•. Some who speculatively subvert 
 m the distinction of vice and vir- 
 
 tue are practically virtuous. = I .'. Some S is P. 
 
 Dimaris is a valid mood, since it conforms to the Canon, in its universal 
 minor premise, A, and its particular conclusion, I. 
 
 ^ No negro is a Hindoo ; = E No P is H ; 
 gj All Hindoos are blacks ; = A All M is S ; 
 £ .'. Some blacks are not ne- 
 ^ groes. = .'. Some S is not P. 
 
 Fesapo is a valid mood, since it conforms to the Canon, in its universal major 
 premise, E, its universal minor premise, A, and its particular conclusion, O. 
 
 No moral principle is an 
 o animal impulse ; = E No P is M ; 
 
 ••2 Some animal impulses are 
 
 principles of action ; = I Some M is S ; 
 Some principles of action 
 10 are not animal impulses. = .'. Some S is not P. 
 
 Fresison is a valid mood, since it conforms to the Canon, in its universal 
 major premise, E, and in its particular conclusion, O. 
 
 h 
 
 <&> 
 
 Figure IV. is the reverse of Figure I. It is naturally and uncon- 
 sciously used, according to Lambert, to prove reciprocities. He found3 
 it on a " Dictum de reciproco :" " If no XL is B, no B is this or that M ; 
 if C is or is not this or that B, there are B which are or are not C." 
 
176 PRACTICAL LOGIC. 
 
 IV. Collected Results. 
 
 For convenient reference the results of the testing of the 
 various forms may be gathered up and tabulated. 
 
 1. Table of Moods, Valid and Invalid. 
 
 i~ CD 
 
 ™ ft 
 
 ^ ft 
 
 A 
 
 
 
 "o 
 
 o 
 O 
 
 A 
 
 E 
 I 
 
 
 
 Moods. 
 
 Tested. 
 
 Si 
 
 E. 
 
 da 
 
 2 2 
 ^ft 
 
 3 
 
 PI 
 o 
 O 
 
 Moods. 
 
 Tested. 
 
 
 AAA 
 
 AAE 
 A AI 
 
 A AO 
 
 V. C. i. 
 
 I. C. 2. 3. 4. 
 
 I. P. 1. 
 
 V. C. i (W). 3. 4- 
 
 I. C. 2. 
 
 I. P. 1. 
 
 A 
 
 A 
 
 E 
 
 I 
 
 
 EAA 
 EAE 
 
 E AI 
 EAO 
 
 I. P. 2. 
 
 V. C. I. 2. 
 
 I. C. 3. 4. 
 
 I. P. 2. 
 
 V. C. 2 (W). 3. 4- 
 
 I. C. 1. 
 
 A. 
 
 E 
 
 A 
 E 
 
 I 
 
 
 AEA 
 AEE 
 
 AEI 
 AEO 
 
 I. P. 2. 
 
 V. C. 2. 4. 
 
 I. C. 1. 3. 
 
 I. P. 2. 
 
 V.C.2 (W).4.(W). 
 
 I. C. 1. 3. 
 
 E 
 
 A 
 E 
 
 I 
 
 
 EE A 
 EEE 
 
 EEI 
 EEO 
 
 I. P. 3. R. 5. 
 I. P. 3. R. 5. 
 
 I. P. 3. R. 5. 
 I. P. 3. R. 5. 
 
 I 
 
 A 
 E 
 I 
 
 O 
 
 AIA 
 AIE 
 All 
 
 AIO 
 
 I. R. 4. 
 I. P. 1. R. 4. 
 V. C. i. 3. 
 I. C. 2. 4. 
 I. P. 1. 
 
 I 
 
 A 
 
 E 
 I 
 
 
 
 EI A 
 EIE 
 EH 
 
 EIO 
 
 I. P. 2. R. 4. 
 I. R. 4. 
 I. P. 2. 
 
 V. C. i. 2. 3. 4. 
 
 
 
 
 A 
 E 
 I 
 
 
 AO A 
 AOE 
 AOL 
 AOO 
 
 I. P. 2. R. 4. 
 I. R. 4. 
 I. P. 2. 
 
 V. C. 2. 
 
 I. C. 1. 3. 4. 
 
 
 
 A 
 E 
 I 
 
 
 EO A 
 EOE 
 EOI 
 EOO 
 
 [I. P. 3. R. 4. 
 I. P. 3. R. 4. 5. 
 I. P. 3. R. 5. 
 I. P. 3. R. 5. 
 
 
 A 
 
 A 
 E 
 
 I 
 
 
 
 IAA 
 I AE 
 I AI 
 
 IAO 
 
 I. R. 4. 
 I. P. 1. R. 4. 
 V. C. 3. 4- 
 I. C. 1. 2. 
 I. P. 1. 
 
 0. 
 
 A 
 
 A 
 
 E 
 
 I 
 
 
 A A 
 AE 
 OAI 
 OAO 
 
 I. P. 2. R. 4. 
 I. R. 4. 
 I. P. 2. 
 V. C. 3. 
 I. C. 1. 2. 4. 
 
 I. 
 
 E 
 
 A 
 E 
 I 
 
 
 I EA 
 IEE 
 IEI 
 IEO 
 
 I. P. 2. R. 4. 
 I. R. 4. 
 I. P. 2. 
 I. R. 7. 
 
 E 
 
 A 
 
 E 
 I 
 
 
 OEA 
 OEE 
 OEI 
 OEO 
 
 I. P. 3. R. 4. 5. 
 I. P. 3. R. 4. 5. 
 I. P. 3. R. 5. 
 I. P. 3. R. 4. 5. 
 
 I 
 
 A 
 
 E 
 
 I 
 
 
 IIA 
 HE 
 III 
 HO 
 
 I. P. 3. R. 6. 
 I. P. 1. 3. R. 4. 6. 
 I. P. 3. R. 6. 
 I. P. 1. 3. R. 6. 
 
 I 
 
 A 
 E 
 
 I 
 
 
 OIA 
 OIE 
 OH 
 010 
 
 I. P. 2. 3. R. 4. 6. 
 I. P. 3. R. 6. 
 I. P. 2. 3. R. 4. 6. 
 I. P. 3. R. 6. 
 
 
 
 
 A 
 E 
 I 
 
 
 10 A 'LP. 2. 3. R.4.5. 
 I E I. P. 3. R. 4. 6. 
 I I I. P. 2. 3. R. 4. 6. 
 10 I. P. 3. R.6. 
 
 
 
 A 
 E 
 I 
 
 
 00 A 
 OOE 
 001 
 000 
 
 I. P. 3. R. 4. 5. 6. 
 I. P. 3. R. 4. 5. 6. 
 I. P. 3. R. 4. 5. 6. 
 I. P. 3. R. 4. 5. 6. 
 
 Note.— In the column headed "Tested," V denotes valid; I, invalid; P, 
 principle; R,rule; C,both canon and figure; W, weak (indicating a partic- 
 ular conclusion where a universal might be drawn). The student will find 
 profitable exercise in applying the tests to all the forms and figures. 
 
THE UNFOLDING OF REASONING. 
 
 177 
 
 2. Things Proved by the Figures. 
 Fig. Proved. Process. 
 
 I. Attribute. 
 
 II. Difference. 
 
 III. Example. 
 
 IV. Beciprocity. 
 
 Ascribes to the thing what we 
 know of its attribute. It con- 
 cludes from the genus to the 
 species. 
 
 Leads to the discrimination of 
 things, and relieves perplex- 
 ity in our notions. Affords 
 only negative conclusions. 
 
 Affords examples and excep- 
 tions in propositions which 
 appear general. Gives only 
 particular conclusions. 
 
 Finds species in a genus in Bra- 
 mantip and Dimaris; shows 
 that the species does not ex- 
 haust the genus in Fesapo 
 and Fresison ; denies of the 
 species what was denied of 
 the genus in Camenes. 
 
 Dictum. 
 
 Dictum de Omni et 
 Nullo. What is 
 true of all A is 
 true of every A. 
 
 Dictum de Diverso. 
 Things which are 
 different are not 
 attributes of each 
 other. 
 
 Dictum de Exem- 
 plo. When we find 
 things A which 
 are B, in that case 
 some A are B. 
 
 Dictum de Recip- 
 roco. If no M is B, 
 no B is this or that 
 M; if C is (or is 
 not)thisorthatB, 
 there are B which 
 #re (or are not) C. 
 
 3. Valid Moods in the Four Figures. 
 
 The valid moods in all the Figures have been embodied in five Latin 
 hexameter lines : 
 
 Fig. 1. Barbara, Celarent, Darii, Feriogwe prions; 
 Fig. 2. Cesare, Camestres, Festino, Baroko (or Fakofo), secundce ; 
 Fig. 3. Tertia Darapti, Disamis, Datisi, Felapton, 
 
 Dokamok (Bokardo), Ferison habet. Quarta insuper addit 
 Fig. 4. Bramantip, Camenes, Dimaris, Fesapo, Fresison. 
 
 V. Eednction of Figures. 
 
 Figure I. has been looked upon by logicians as the normal Figure, 
 to which all the others may be reduced. The object of Logical Reduc- 
 tion is to bring arguments of the last three Figures into the form of 
 Figure I., and thus bring all alike to the test of Aristotle's Dictum. It 
 is thus shown that this Dictum, which is clearly the regulating prin- 
 ciple in Figure I., is also the regulating principle in all deductive rea- 
 
 M 
 
178 PRACTICAL LOGIC. 
 
 soning, and that the process is, therefore, always substantially the 
 same (p. 138). 
 
 Note.— Reduction is usually described as being of two kinds: Direct or Os- 
 tensive, and Indirect (Reductio ad impossibile). The latter method was the re- 
 sult of a mistaken notion of the logicians that Baroco and Bocardo could not 
 be directly reduced, and is of no value theoretical or practical. Fakofo and 
 Dokamok will be substituted for Baroco and Bokardo, and may be reduced 
 by the direct method. 
 
 The mnemonic words in the last three Figures were designed to in- 
 dicate not only the mood of syllogisms, but also the principles by which 
 they are to be reduced. The valid forms in the four Figures must be 
 kept in view in reduction. 
 
 The initial consonant, B, C, D or F, in the last three Figures indi- 
 cates the mood in the first Figure to which the syllogism reduces. 
 Thus, a syllogism in the mood Cesare, Fig. II., reduces to Celarent. 
 
 The inserted consonants, s, p, k, f, m, indicate the various processes 
 in reduction. S indicates that the proposition symbolized by the vowel 
 preceding it is to be converted simply (p. 127) ; p, by limitation or per 
 accidens (p. 127) ; k, by contraposition (p. 128) ; f, by infinitation or 
 obversion (p. 124). The letter m (mutari) indicates that the premises 
 of the preceding judgment are to be transposed. The p in Braman- 
 tip shows that, after converting simply, the premises warrant a uni- 
 versal conclusion. 
 
 The other consonants, b, d, 1, n, r, t, are not significant, but are in- 
 serted for the sake of euphony, or of the metre in the mnemonic hex- 
 ameters invented, to keep the moods and figures in mind, by Petrus 
 Hispanus, who died in 1277 as Pope John XXII. 
 
 The process of reduction may be illustrated by the following examples : 
 Figure II. Figure I. 
 
 No P is M ; f No M is P ; 
 
 Cesare = { All S is M ; Celarent = \ All S is M ; 
 
 -L 
 
 ..♦. NoS. is P. U*. No Sis P. 
 
 Bash fulness is not something thor- 
 oughly good ; 
 Modesty is something thoroughly 
 good; 
 .-. Modesty is not bashfulness. 
 
 Nothing thoroughly good is bash- 
 fulness ; 
 
 Modesty is something thoroughly 
 good; 
 
 Modesty is not bashfulness. 
 
 The C in Cesare indicates that the mood reduces to Celarent; the s,that the 
 major premise is to be converted simply. 
 
 Figure III. Figure I. 
 
 C AllMisP; r AllMisP; 
 
 Darapti = \ All M is S ; Darii = -j Some S is M ; 
 
 ( /. Some S is P. I .*. Some S is P. 
 
THE UNFOLDING OF REASONING. 
 
 179 
 
 All whales are mammalia ; 
 
 All whales are water animals ; 
 . Some mammalia are water animals. 
 
 All whales are mammalia ; 
 Some water animals are whales ; 
 .*. Some mammalia are water animals. 
 
 The D in Darapti indicates that the mood reduces to Darii; the p, that the 
 preceding proposition, A, is to be converted by limitation. 
 
 Note.— The student can readily carry the work of reduction through all the 
 figures and moods. 
 
 Topic Third. — Complex and Abnormal Forms. 
 
 In books and in conversation arguments usually appear 
 in incomplete or irregular forms, and often combined as 
 polysyllogisms manifest or occult. In dealing with these, 
 the incomplete forms, except in the case of such regular 
 forms as the Sorites, need to be completed and the irreg- 
 ular forms reduced to regularity. The general rules then 
 become applicable. 
 
 The greater part of this work the student may be left to carry out 
 for himself by aid of the principles already laid down. There is need, 
 however, to present the principles which govern the Sorites, to con- 
 sider briefly some peculiar forms of argumentation, and to exhibit 
 especially the calculation of probabilities. 
 
 I. The Sorites Tested. 
 
 The Sorites, or chain of Enthymemes in Fig. I., has al- 
 ready been defined and illustrated (p. 143). There are two 
 ways of testing the Sorites : by completing all the abridged 
 syllogisms (p. 144), and then applying the usual tests ; or by 
 using a system of rules which may be immediately applied. 
 The former method may be left to the student himself ; only 
 the latter needs to be illustrated. 
 
 From the nature of the Sorites the following principles result : 
 
 1. The first proposition furnishes the major premise of the first com- 
 pleted syllogism ; the last proposition is the conclusion of the last syl- 
 logism and of the whole chain ; the intermediate propositions are the 
 minor premises of the successive syllogisms. The number of syllogisms 
 must, therefore, equal the number of minor premises. 
 
 2. The major premise of each successive syllogism after the first is 
 furnished by the conclusion of the preceding syllogism. 
 
 The reasoning must conform to the Canon of Fig. I. 
 
180 PRACTICAL LOGIC. 
 
 Rule 1st. — Every major premise must be universal in order to avoid 
 undistributed middle. It follows that only the last proposition in the 
 progressive sorites and the first in the regressive may be particular, since 
 any other particular premise would result in making the conclusion 
 of its syllogism, or the next major premise, particular also. 
 
 Rule 2d. — Every minor premise must be affirmative in order to 
 avoid illicit process of the major term. It follows that only one 
 premise may be negative, the last proposition in the progressive sorites 
 and the first in the regressive, since these only are not minor premises. 
 
 The Sorites and its Rules may be illustrated by the following examples, 
 which are abridged to admit of compact parallel statement : 
 
 Progressive Sorites. Regressive Sorites. 
 
 Some prosperous are avaricious; No discontented are happy ; 
 
 The avaricious are intent on gain ; All intent on gain are discontented ; 
 
 The intent on gain are discontented ; All avaricious are intent on gain ; 
 
 The discontented are not happy ; Some prosperous are avaricious ; 
 
 .\ Some prosperous are not happy. .-. Some prosperous are not happy. 
 
 It has been often asserted that Sorites cannot occur in any other than Fig. I. 
 It has been shown, however, by Mill, that one step, and only one, step in a So- 
 rites may be either in Figure II. or Figure III. 
 
 II. Peculiar Forms of Argumentation. 
 
 The usual form of direct proof of propositions is known 
 among logicians as the argumentum ad rem, or proof of the 
 thing itself. As variations from it or in contrast with it may 
 be noted the argumentum a fortiori, the argumentum ad judi- 
 cium, the argumentum ad populum, the argumentum ad 
 verecundiam, the argumentum ad ignorantiam, the argumen- 
 tum ad hominem y and the reductio ad absurdum. 
 
 The argumentum a fortiori, or, " by a stronger reason," is one involving com- 
 parative judgments. It is based upon the maxim, " What is greater than a 
 greater is greater still than the thing." The argument is essentially mathe- 
 matical or qualitative. Thus : 
 
 Asia is larger than Africa ; 
 Africa is larger than Europe ; 
 ,\ By much more is Asia larger than Europe. 
 This may also be presented as follows : 
 
 The Atlantic Ocean is as large as Lake Superior (and more) ; 
 Lake Superior is as large as the Dead Sea (and more) ; 
 .\ The Atlantic Ocean is as large as the Dead Sea (and still more). 
 The argument a fortiori is also denned as " the proof of a conclusion deduced 
 from that of a less probable supposition that depends upon it." For example, 
 gee Matthew vi. 30 and vii. 11. 
 
THE UNFOLDING OF REASONING. 181 
 
 The argumentum ad judicium is based upon the common judgments of man- 
 kind. Its maxim is, " What all men everywhere and always believe, is true," 
 or the so-called principle of common sense on which the Scottish philosophy 
 of Reid rests. The argument has great force when it is really based on the 
 common judgment of mankind. The danger of appealing to this principle 
 without sufficient grounds is, however, very great. Under the confident asser- 
 tions, " Everybody says," " No one pretends to think," the greatest fallacies 
 are often covered. The argument may be illustrated as follows : 
 
 The material world is a reality and our perception of it immediate, because 
 all men, everywhere and always, have so believed. 
 
 The argumentum ad populum is based on an appeal to public opinion, or to 
 passion or prejudice, rather than intelligence. It is often employed because 
 no really good arguments are to be found, or because it is easier to appeal to 
 the passions and prejudices of the masses than to their intelligence. It often 
 puts forward as its major premise the false maxim, " Vox populi Vox Dei" 
 " The voice of the people is the voice of God." 
 
 The argumentum ad verecundiam is an appeal to the feelings of reverence 
 for certain persons or objects, instead of proceeding to prove the point in hand. 
 The Scholastics used as a standing major premise the maxim, " It is foolish to 
 affirm that Aristotle erred." 
 
 The argumentum ad ignorantiam is addressed to the ignorance of men. It 
 sometimes consists in assuming that a position is correct because an adversary 
 cannot show the contrary; sometimes, in taking advantage of men's ignorance 
 to impose upon them by some shallow sophism, false statement, or confident 
 assertion. 
 
 Under this may be included the Fallacy of Interrogation, in which a question 
 is so put as to be equivalent to a confident assertion of some error. The de- 
 mand for an adequate conception (p. 91) or description, often made by a brow- 
 beating lawyer upon a witness in court, is of the same character. It is only a 
 few experts who can give anything more than a clear notion (p. 91) of the 
 handwriting, features, or dress of the most intimate friend. 
 
 The argumentum ad hominem is an appeal to the practice, principles or 
 professions of an opponent as confirming our own position or destructive to 
 his. An opponent may thus be silenced, since the argument is good against 
 him, even though it be not good against the views he advocates. As soon as he 
 renounces such practice, principles or professions, the argument ceases to be 
 of value as against him. Our Lord often used this method to silence the cavils 
 of the Jews ; for example, Matthew xxii. 41-45. 
 
 The reductio ad absurdum proves a proposition indirectly by proving the 
 absurdity of its contradictory. It has already been considered (p. 129). 
 
 III. Calculation of Probabilities. 
 
 The theory of probabilities, or of chances, as it is some- 
 times designated, has in recent times received increased 
 attention. In an elementary work there is only space for 
 the simplest rules and cases. 
 
 Thomson has described chance as " the amount of belief with which we 
 expect one or other, out of two or more uncertain events." Uncertain, 
 16 
 
182 PRACTICAL LOGIC. 
 
 or merely probable, events are " those wherein no cause or law appears 
 to determine the occurrence of one rather than another." Jevons pro- 
 poses "to dispense altogether with this obscure word 'belief,' and to 
 say that the theory of probability deals with quantity of knowledge." 
 An event is merely "probable when our knowledge of it is diluted 
 with ignorance, and exact calculation is needed to discriminate how 
 much we do and do not know." 
 
 At the basis of the rules for the calculation of probabilities are the common- 
 sense principles which underlie all reasoning. " We must treat equals equally, 
 and what we know of one case may be affirmed of every case resembling it in 
 the necessary circumstances. The theory consists in putting similar cases on 
 a par, and distributing equally among them whatever knowledge we possess. 
 Throw a penny into the air, and consider what we know with regard to its 
 way of falling. We know that it will certainly fall upon a side, so that either 
 head or tail will be uppermost ; but as to whether it will be head or tail, our 
 knowledge is equally divided. Whatever we know concerning head, we know 
 also concerning tail, so that we have no reason for expecting one more than 
 the other. The least predominance of belief to either side would be irra- 
 tional ; it would consist in treating unequally things of which our knowledge 
 is equal." 
 
 The Rules concern either simple or combined probabilities. 
 
 Rule 1st. — A single probability of any uncertain event is ascer- 
 tained by dividing the number of chances favorable to the event by 
 the total number of chances favorable and unfavorable. 
 
 Thus the probability that the head will fall uppermost, when a penny is 
 thrown into the air, is expressed by y 2 . The probability that a man blind- 
 folded will draw a white ball out of an urn containing 2 white balls and 8 
 black ones is expressed by & or £. To take a different case, if the letters of the 
 word Roma are thrown down casually in a row, what is the probability that 
 they will form a significant Laxin word ? The possible combinations of the 
 four letters are 4 X 3 X 2 X 1 = 24. If all the combinations are examined, 7 will 
 be found to have a meaning, namely, Roma, ramo, oram, mora, maro, armo, and 
 amor. Hence the probability sought is ^. 
 
 Kule 2d. — The probability of the independent recurrence of an 
 event is found by multiplying together the fractions expressing the 
 single probabilities. 
 
 Thus the probability of throwing head twice with a penny is % X K = M\ 
 the probability of throwing it three times is KX^X^ = ^. This Rule will 
 be seen to rest on Rule 1st, since the denominator represents the possible com- 
 binations in the case, or the whole number of ways of the happening of the 
 compound event, and the numerator the number of ways favorable. 
 
 Rule 3d. — " In order to calculate the probability that an event al- 
 ready observed will be repeated any given number of times, divide 
 the number of times the event has been observed, increased by one,, 
 
THE UNFOLDING OF REASONING. 183 
 
 by the same number increased by one and the number of times the 
 event is to recur." 
 
 " Thus, if the tide had been observed 9 times, the chance that it would recur 
 
 10 times more would be & , 1 n +l==.l£-:=.l This is the same thing as if 
 
 each reproduction of the observed event corresponded to putting a white ball 
 in an urn where there were already, before commencing the trials, a white 
 ball and as many black balls as it is supposed that the event observed should 
 re-occur times." 
 
 Two or more probabilities if mutually dependent weaken each other, 
 while if independent they strengthen each other. 
 
 Bule 4th. — In case of mutually dependent probabilities, or prob- 
 abilities of probabilities, the total probability is reached by multiply- 
 ing together the several single probabilities. 
 
 Thus, if the credibility (p. 105) of a witness be % and his competency (p. 
 104), or ability to know the facts of which he testifies, be %, the total probabil- 
 ity of his telling the truth is % X % = § = >3- As certainty is represented by 
 unity, the testimony will, in this case, be twice as likely to be false as it is to 
 be true. 
 
 Rule 5th. — In case of independent probabilities the total probabil- 
 ity is reached by subtracting each separate probability from unity 
 (which gives the probability of the opposite event, in each case, or the 
 probability of a probability), multiplying the separate results together 
 (according to Rule 4th), and subtracting this product from unity 
 (thus arriving at the probability of the original compound event). 
 
 Thus, the total probability that the Gospels are true may be made up from 
 the probability arising from the character of the authors, represented by % . 
 from the absence of any motive on the part of the authors to fabricate such 
 accounts, represented by % ; from the influence of the Gospels themselves 
 upon the world, represented by f . Subtracting each of these from unity and 
 multiplying the results together, we have, as the probability of imposture, 
 %XMXi = io. This subtracted from unity gives f§ as the probability of the 
 truth of the Gospels. 
 
 Note.— See Thomson's Laws of Thought; Jevon's Principles oj Science; New- 
 comb's Algebra, 
 
 Praxis. — In the following syllogisms show whether the premises 
 are true. Name the middle, minor, and major terms. Name the mood 
 and figure of each, showing whether valid or not. Reduce any mood 
 in the other Figures to Fig. L Bring out the relation of reason and 
 consequent involved in connection with the middle term in each case, 
 substituting the letters, S, P, M, for the terms in the general formula, 
 and giving the relation of the notions by the circular notation. 
 
 1. No human weakness can belong to God; some attributes imputed 
 
184 PRACTICAL LOGIC 
 
 to the Deity by mythology are human weaknesses ; hence (at least) 
 some attributes imputed to the Deity by mythology cannot belong to 
 Him. 
 
 2. Some who act in accordance with law do not do what is right 
 with right intention ; .*. some who act legally are not morally disposed. 
 
 3. Every real, natural poem is naive; those poems of Ossian which 
 Macpherson pretended to discover are not naive (but sentimental) ; 
 hence they are not real, natural poems. 
 
 4. The sum total of the worlds belonging to our solar system must 
 completely determine the orbit of Uranus ; the known worlds of our 
 solar system do not fully account for the orbit of Uranus ; hence the 
 whole of the worlds of our solar system are not known. 
 
 5. Passive mental states make men neither noble nor base, worthy 
 of praise or of blame ; the virtues do this ; .*. the virtues are not pass- 
 ive mental states. 
 
 6. All squares are rectilineal plane figures ; some parallelograms 
 are squares ; .*. some parallelograms are rectilineal plane figures. 
 
 7. No form of knowledge, which corresponds to a peculiar form of 
 existence, is of merely didactic value ; syllogism is a form of knowledge 
 which corresponds to a peculiar form of existence (viz., to the real con- 
 formability to law) ; hence the syllogism is not of mere didactic worth. 
 
 8. All cetaceous animals are water animals ; all cetaceous animals 
 are mammalia ; hence some mammalia are water animals. 
 
 9. Some persons accused of witchcraft have not believed themselves 
 to be free from the guilt laid to their charge; all those accused of 
 witchcraft were accused of a merely feigned crime ; hence some who 
 were accused of a merely feigned crime have not believed themselves 
 free from the guilt laid to their charge. 
 
 10. Jubeo is not a verb sentiendi vel declarandi ; jubeo takes the con- 
 struction of the accusative and infinitive ; hence at least one or some 
 Latin verbs which take the construction of accusative and infinitive 
 are not verbs sentiendi vel declarandi. 
 
 11. All squares are regular figures ; some parallelograms are squares ; 
 .*. some parallelograms are regular figures. 
 
 12. Some parallelograms are squares ; all squares are regular figures; 
 ,\ some regular figures are parallelograms. 
 
 13. All squares are parallelograms ; no parallelogram has converg- 
 ing opposite sides ; .*. no square has converging opposite sides. 
 
 14. Good non-conductors of heat retain heat longer ; woollen clothes 
 are good non-conductors ; .'. woollen clothes retain heat longer. 
 
 15. Some things which retain heat longer are woollen clothes ; things 
 
THE UNFOLDING OF REASONING. ' 185 
 
 which retain heat longer are good non-conductors ; ,\ woollen clothes 
 are good non-conductors. 
 
 Supply the conclusions to each of the following pairs of premises, 
 and show whether the conclusion is valid, or why no conclusion can 
 be drawn. Treat the syllogisms as required in the preceding examples. 
 
 1. All good reasoners are candid; some infidels are not candid; 
 
 2. The ox, deer, sheep, goat, etc., are ruminant; the ox, the deer, 
 etc., are as good as all horned animals ; .* 
 
 3. Oaks are vegetables ; oysters are not oaks ; .' 
 
 4. No good action results in evil ; some alms-giving results in evil ; 
 
 5. Animals are bodies having organization and sensation; frogs 
 have organization and sensation ; .* 
 
 6. Some of our tax laws are oppressive measures; all oppressive 
 measures should be repealed ; / 
 
 7. Reptiles bring forth their young by eggs ; the rat does not bring 
 forth its young by eggs ; .* 
 
 8. The connection of soul and body is to be believed ; the connec- 
 tion of soul and body is incomprehensible ; .' 
 
 9. True poets are men of genius ; very unwise men have proved 
 true poets ; .* 
 
 10. All good men are sincere ; Eousseau was sincere ; / 
 
 11. Political Economy is a profitable study ; profitable study 
 sharpens the intellect ; .' 
 
 12. No truth is worthless ; many truths are misapplied ; .' 
 
 13. Most people are careless ; most people are destitute of perfect 
 health; .' 
 
 14. 90 out of every 100 men are imprudent ; 90 out of every 100 
 are unsuccessful ; .* 
 
 15. Elephants are stronger than horses ; horses are stronger than 
 men ; / 
 
 Section II.— Unfolding of the Hypothetical Syllogism. 
 Hypothetical syllogisms have already been defined and 
 divided (pp. 144-146). They will now be considered in the 
 order of the division given. 
 
 Topic First. — The Conditional or Conjunctive Syllogism. 
 
 The conditional syllogism may either be tested as it is, 
 16* 
 
186 PRACTICAL LOGIC. 
 
 or reduced to categorical form and then tested by the prin- 
 ciples of categorical reasoning. 
 
 I. The Tests of Conditional Syllogisms. 
 
 The tests of conditional syllogisms arise out of their na- 
 ture as directly embodying the principle of Eeason and 
 Consequent. From this it follows that, if the reason be 
 present in any given case we may be sure of the presence 
 of the consequent ; and if the consequent be absent we may 
 be sure of the absence of its reason. Hence the two forms 
 of conditionals, the constructive and destructive, and the 
 Eules applicable to these forms of reasoning. 
 
 Rule 1st. — Affirming the antecedent or reason affirms the conse- 
 quent [modus ponens) ; while denying the consequent denies the ante- 
 cedent (modus tollens). 
 
 The first part of the Rule gives the constructive conditional, which 
 affirms the reason or antecedent, and then on the ground of this af- 
 firms the consequent. The second part gives the destructive condi- 
 tional, which denies the consequent, and on the ground of this denies 
 the reason. The two forms may be illustrated as follows : 
 
 .> Antecedent. Consequent. 
 
 3 If General Grant has a fever, he is sick ; Major premise. 
 
 % He has a fever; {Modus ponens). Minor premise. 
 
 g .*. He is sick. Conclusion. 
 
 o 
 
 3 If General Grant has a fever, he is sick ; Major premise. 
 
 § He is not sick; (Modus tollens.) Minor premise. 
 
 > Antecedent. Consequent, 
 
 If General Grant has a fever, he is sick ; 
 
 He is not sick ; (Modus tollen 
 q .-. He has not a fever. Conclusion. 
 
 The absence of the particular reason or antecedent mentioned in any 
 given case does not render certain the absence of the consequent, since 
 antecedents or reasons are manifold and the consequent may follow 
 from other antecedents. So the presence of the consequent does not 
 argue the presence of a particular antecedent or reason, since it may 
 be the consequent or effect of some other antecedent. Hence 
 
 Rule 2d. — Denying the antecedent does not deny the consequent ; 
 and affirming the consequent does not affirm the antecedent. 
 
THE UNFOLDING OF REASONING. 187 
 
 Antecedent. Consequent. 
 
 ( If there is fire in the stove ; the room will he warm ; Major premise. 
 
 •s There is no fire in the stove ; (Deny Ant.) Minor premise. 
 
 ( ." No conclusion. 
 
 If there is fire in the stove ; the room will be warm ; Major premise. 
 
 The room is warm. (Affirm Conseq.) Minor premise. 
 
 .* No conclusion. 
 
 In the case of the denial of the antecedent the conclusion that the 
 room will not be warm does not follow, since it may be warmed by a 
 grate, or a furnace, or steam apparatus, or a warm sun in summer, or 
 the presence of a large audience, or by being on fire, etc. In the case 
 of the affirmation of the consequent, the particular antecedent does 
 not follow, since the same thing may result from any one of the ante- 
 cedents enumerated. 
 
 The whole may be illustrated by diagram : 
 
 jg __ Furnace. ~~ "-— __ ~^ ^.^ 
 
 •g ~~~ ^r ^-. Heated "g 
 
 o Steam. --tr?-==-- § 
 
 BO ----V^U © 
 
 S Sun. ~~~__--"~:>'"" § 
 
 <3 „,— — ^- Koom. ^ 
 
 The dotted lines may represent the possible lines of reason or causa- 
 tion ; the heated room, the consequent or effect. If the stove is pres- 
 ent, then the heated room will be present, because that is a sufficient 
 reason. If the stove is not present, the room may still be heated, since 
 the grate, furnace, etc., may furnish the sufficient reason. If there is 
 not the heated room, then all the antecedents must be absent, — stove, etc. 
 If there be the heated room, no definite a priori conclusion concerning 
 the agency of the stove is possible, since the consequent may result 
 from any other of the antecedents. 
 
 II. Reduction of the Conjunctive Syllogism. 
 
 The conjunctive or conditional syllogism may readily be 
 reduced to the categorical form, as already shown (p. 117), 
 
188 PRACTICAL LOGIC. 
 
 and then tested by the Rules which apply to the various 
 Figures. 
 
 Applying the principles of reduction to the syllogism just given, it 
 becomes : 
 
 i st. The case of the presence of the heated stove is the case of a warm room ; 
 
 The present is the case of a heated stove ; 
 * /. The present is the case of a warm room. 
 »i 
 JOrA.: Every room in which a stove is heated is warm ; 
 
 £ A. This is a room in which a stove is heated ; 
 A. .*. This room is a warm room. 
 
 JJ 2d. A. Every room in which the stove is heated is warm ; 
 
 •3 E. This room is not warm ; 
 
 r E. .*. The stove is not heated in this room. 
 
 3 
 
 * 3d. A. Every room in which the stove is heated is warm ; 
 E. This is a room in which the stove is not heated ; 
 ,§p E. .*. This room is not warm. (Not valid.) 
 
 This form corresponding to the denial of the antecedent, under Rule 2d, in- 
 volves illicit process of the major term.' 
 
 % 4th. A. Every room in which the stove is heated is a warm room ; 
 3 A. This room is a warm room ; 
 
 •- A. .*. This room is one in which the stove is heated. (Not valid.) 
 
 m 
 
 This form corresponding to the affirming of the consequent, under Rule 2d, 
 involves undistributed middle, or substantially four terms. 
 
 Topic Second. — The Disjunctive Syllogism. 
 
 The tests of the disjunctive syllogism arise out of the na- 
 ture of the disjunctive judgment, as embodying the prin- 
 ciple of Excluded Middle, in connection with Reason and 
 Consequent the principle of all reasoning. 
 
 A perfect disjunctive judgment embodies a complete division of some 
 genus or class, and the alternatives presented are trie species under 
 that class, and are reciprocally exclusive (p. 71). 
 
 The major premise presents these species as alternatives. 
 
 The minor premise makes a categorical predication concerning one 
 or other of the species or alternatives. 
 
 The conclusion draws an inference concerning the other species. 
 
 Rule 1st. — See that the disjunction exhausts the division, and that 
 the disjunctives are reciprocally exclusive. 
 
 Rule 2d. — Affirming a part of the disjunctives, wholly or disjunc- 
 tively, in the minor premise, denies all the others in the conclusion. 
 
THE UNFOLDING OF REASONING. 189 
 
 Rule 3d. — Denying a part of the disjunctives, in the minor prem- 
 ise, affirms the rest, in the conclusion, wholly or disjunctively, ac- 
 cording as one or more may remain. 
 
 These may be illustrated by the following examples : 
 
 The Apostles must have been fanatics, or imposters, or true men ; 
 
 They were neither fanatics nor imposters ; 
 
 .*. They were true men. 
 
 The season of the battle of Lexington must have been spring, or summer, or 
 
 autumn, or winter ; 
 It was neither summer nor winter ; 
 ,\ It was either autumn or spring. 
 
 In the first example the character of the Apostles is analyzed into 
 three possible exclusive phases, and we affirm that if they do not be- 
 long to one or other of the first two they must belong to the third. In 
 the second example the seasons are analyzed into the four, and we af- 
 firm that since it was neither the second nor fourth it was one of the 
 other two. 
 
 Topic Third. — The Dilemmatic Syllogism. 
 
 The dilemmatic, or conjunctivo-disjunctive, syllogism is 
 subject to the Rules of conditionals and disjunctives. The 
 most common forms are the following : 
 
 I. One Antecedent in the Major with Disjunctive Consequent. 
 
 This takes the form : If A is B, either C is D or E is F. By the 
 rules of conditionals and disjunctives we have the following possible 
 cases and results : 
 
 Affirm Antecedent. A is B ; .*. either C is D or E is F. 
 
 Deny Cons, wholly. Neither C is D nor E F ; .'. A is not B. 
 
 Deny Cons, disjunctively. Either C is not D or E is not F. No conclusion. 
 
 Denied of Antecedent. A is not B. No conclusion. 
 
 Affirmation of Consequent. C is D or E is F No conclusion. 
 
 II. Plurality of Antecedents in the Major with Common Consequent. 
 
 This takes the form : If A is B, X is Y, and if C is D, X is Y. This 
 gives the following cases and results : 
 
 Affirm Antec. wholly. A is B and C is D ; .*. X is Y. 
 
 Affirm Antec. disjunct. A is B or C is D ; .*. X is Y. 
 
 Deny Consequent. X is not Y ; .*. neither A is B nor C is D. 
 
 Deny Antecedents. A is not B nor is C D. No conclusion. 
 
 Affirm Consequent. X is Y. No conclusion. 
 
 III. Plurality of Antecedents in Major, each with its own Conse- 
 quent. 
 
190 PRACTICAL LOGIC. 
 
 This takes the form: If A is B, C is D, and if E is F, G is H. This 
 gives the following oases and results : 
 
 Affirm Ant. wholly. A is B and E is F ; ,\ C is D and G is H. 
 
 Affirm Ant. disjunct. A is B or E is F ; /. C is D or G is H. 
 
 Deny Cons, wholly. C is not D and C is not H ; /.A is not B and E is not F. 
 
 Deny Cons, disjunct C is not D and G is not H ; .*. A is not B or E is not F, 
 
 Deny Antecedent. A is not B and E is not F. No conclusion. 
 
 Affirm Consequent. C is D and G is H. No conclusion. 
 
 Note.— All the forms enumerated are called dilemmatic syllogisms, but, as 
 already stated (p. 146), the dilemma, in the strict sense, is only that form which 
 has a plurality of antecedents in the major, and a disjunctive minor. This 
 dilemma is sometimes rebutted by another with an opposite conclusion. Aris- 
 totle illustrates the process of rebuttal thus : " An Athenian mother said to her 
 son, ' Do not engage in public affairs ; for if you do what is just men will hate 
 you, and if you do what is unjust the gods will hate you.' This the son re- 
 butted by the following retort : ' I ought to enter into public affairs ; for if I do 
 what is unjust men will love me, and if I do what is just the gods will love 
 me.' " 
 
 Praxis. — In the following examples, complete the syllogisms if in- 
 complete. Name the kind in each case and formulate with letters and 
 illustrate by diagram. Test each example by the Kules. 
 
 1. If men are virtuous they are wise, and if they are vicious they 
 
 are unwise ; 
 But they are either virtuous or vicious ; 
 .*. They are either wise or unwise. 
 
 2. If the classics teach how to produce wealth they ought to be 
 
 studied ; 
 They do not so teach ; 
 .*. They ought not to be studied. 
 
 3. Mahomet was either an enthusiast or an impostor; 
 He was an enthusiast ; 
 
 .*. He was not an impostor. 
 
 4. If there be no future life, then either virtue receives its due re- 
 ward in the present world, or there is no perfect government admin- 
 istered over men ; neither of which is admissible. 
 
 5. The fact that I defended him is a proof that I hold him innocent. 
 
 6. If pain is severe, it will be brief; and if it last long, it will be 
 slight ; hence it should be borne patiently. 
 
 7. If this man were wise, he would not speak irreverently of Scrip- 
 ture in jest, and if he were good, he would not do so in earnest; 
 
 But he does it either in jest or in earnest ; 
 
TEE UNFOLDING OF REASONING. 191 
 
 Section III.— Conspectus of Fallacies. 
 A fallacy is any unsound or delusive mode of reasoning. 
 The principal fallacies in induction and deduction need to be 
 particularized and distinguished. 
 
 In order to acquire a complete command of the principles of reason- 
 ing and to guard against error, the thinker must make himself familiar 
 with the most common kinds of fallacy. In the previous Sections, as 
 Jevons has said, " we have considered, as it were, how to find the right 
 road ; it is our task here to ascertain the turnings at which we are 
 most liable to take the wrong road." 
 
 Note.— With respect to the knowledge or intention of the reasoner, fallacies 
 have been divided into paralogisms and sophisms. A paralogism is a fallacy 
 which is unknown to the reasoner himself; a sophism is a false argument, un- 
 derstood to be so by the reasoner himself and intentionaUy used to deceive, 
 This is not, however, a logical distinction, since it is not based upon the thought, 
 but upon the mental and moral condition of the reasoner, and is, therefore, of 
 no logical value. 
 
 Topic First. — Fallacies in Induction. 
 
 In induction we deal with matters of fact. The require- 
 ments of induction are summed up in two things : 
 
 1st. Exact Observation of the facts. 
 2d. Correct Interpretation of the facts. 
 
 All fallacies in induction arise from failure to conform to 
 these requirements. 
 
 I. Fallacies from Failures in Exact Observation. 
 
 1. Neglect of observation, or ignoring of all facts (pp. 26-34, 148, 
 155). 
 
 2. Partial observation, giving incomplete view of the facts (pp. 33, 
 148, 155). 
 
 3. Neglect of exceptional, and especially contradictory, facts (p. 155). 
 
 4. Assuming what is not fact to be fact (pp. 33, 148). 
 
 5. Mixing illegitimate inferences with the facts (p. 33). 
 
 II. Fallacies from Failures in Correct Interpretation. 
 
 1. Neglect of all cause, or confounding induction with mere general- 
 ization (pp. 147, 153), including groundless universal conclusion from 
 few unimportant facts (fictce universalitatis) (p. 159). 
 
 2. Partial explanation of the facts, by assuming an improper or in- 
 sufficient cause, including: 
 
192 PRACTICAL LOGIC 
 
 (1.) Assuming inappropriate cause (p. 154). 
 
 (2.) Assuming inadequate cause (p. 154). 
 
 (3.) Assuming a single cause where there is a complex of causes (p. 154). 
 
 3. Neglect of real cause for hypothetical cause (p. 154). 
 
 4. Fallacy of unreal reason, or assuming what is not a cause to be a 
 cause {non causa pro causa) (p. 160), including: 
 
 (1.) Confounding antecedent and cause (post hoc ergo propter hoc) (p. 149). 
 
 (2.) Confounding concomitant, condition or occasion and cause (cum hoc ergo 
 propter hoc) (p. 149). 
 
 (3.) Confounding law and cause (p. 149). 
 
 Note.— The most noted forms of the fallacy of unreal reason are the lazy 
 reason (ignava ratio), the reaper (ratio metens), and the controlling reason (ratio 
 dominans). These are all of the same character, and may be illustrated by an 
 example of the first, which gave it its name : 
 
 Sumption.—" If I ought to exert myself to effect a certain event, this event 
 either must take place or it must not ; 
 
 Sub-sumption.—" If it must take place, my exertion is superfluous ; if it must 
 not take place, my exertion is of no avail ; 
 
 Conclusion.—" Therefore, on either alternative, my exertion is useless." 
 
 In regard to the vice of this sophism, Krug, as quoted by Hamilton, says: 
 " It is manifest that it lies in the sumption, in which the disjunct members are 
 imperfectly enounced. It ought to have been thus conceived : If I ought to 
 exert myself to effect a certain event, which I cannot, however, of myself 
 effect, this event must either take place from other causes, or it must not take 
 place at all. It is only under such a condition that my exertion can, on either 
 alternative, be useless, and not if the event depend wholly or in part for its 
 accomplishment on my exertion itself, as the conditio sine qua non." 
 . This shows that this so-called syllogism formally violates Rule 1st under 
 disjunctives (p. 188), as applied to the dilemma. 
 
 5. Assuming unverified hypotheses as truth (pp. 156, 160). 
 
 Topic Second. — Fallacies in Deduction or Syllogism. 
 
 Deductive reasoning deals with truths or general princi- 
 ples. Its requirements are, therefore, summed up in two 
 things : 
 
 1st. Correct Matter or Thought, or the grasping of true 
 premises. 
 
 2d. Correct Form in Reasoning, or the proper unfolding 
 of what is contained in the premises. 
 
 All fallacies in deduction result, therefore, from failure to comply 
 with one or both these requirements. Those which result from some 
 failure in the matter or thought are known as Material Fallacies ; 
 those resulting from some failure in the form of reasoning are known 
 
THE UNFOLDING OF REASONING. 193 
 
 as Logical or Formal Fallacies ; those resulting from failure in both 
 matter and form are known as Semi-Logical Fallacies. 
 
 I. Material Fallacies. 
 
 Material fallacies are those which arise outside of the 
 mere form of thought, or verbal statement {extra dictionem), 
 in the subj ect-matter or thought itself. They may take the 
 form of unwarranted assumption of premises, or of irrelevant 
 conclusion from the proper premises. 
 
 1. Unwarranted Assumption of Premises. 
 
 (1.) Begging the question (petitio principii), or virtual assumption 
 of the thing to be proved or of that by which it is to be proved. This 
 includes : 
 
 a. Petitio principii proper, where the assumption is openly made without 
 show of proof. 
 
 b. Arguing in a circle, where the conclusion is virtually used to prove the 
 premise. 
 
 E. g., John Knox and John Witherspoon are excellent men because they be- 
 longed to an excellent church, the Presbyterian Church ; and the Presbyterian 
 Church is an excellent one because it has contained such good men. 
 
 c. Assuming a resemblance without proving it, or where there is no such 
 resemblance (non tale pro tali). 
 
 E. g., " All other religions are delusions ; therefore, Christianity is a delusion." 
 
 (2.) Failure in Estimating Probabilities. 
 
 a. Over-estimation of dependent probabilities (p. 182). 
 
 b. Under-estimation of independent probabilities (pp. 108, 183). 
 
 2. Irrelevant Conclusion from Proper Premises. 
 
 (1.) Fallacy from arguing to the wrong point. This is also called 
 ignoratio elenchi, or "ignoring the refutation," which refutation in- 
 volves the establishment of the contradictory (p. 129). This includes : 
 
 a. Perverted argument from common consent (argumentum ad judicium) 
 (p. 181). 
 
 b. Argumentum ad populum (p. 181). 
 
 c. Argumentum ad verecundiam (p. 181). 
 
 d. Argumentum ad ignoranUam (p. 181). 
 
 e. Argumentum ad hominem (p. 181). 
 
 (2.) Fallacy from simple Confusion of Thought. This includes : 
 
 a. Fallacy of accident (fallacia accidentis) and the converse (p. 167). This 
 includes : 
 
 (a.) Arguing from a general rule to a special case, where some accidental cir- 
 cumstance renders the rule inapplicable. 
 
 (b.) Arguing from a special case to a general one. This is described by the 
 17 N 
 
194 PRACTICAL LOGIC. 
 
 Latin phrase, " a dicto secundum quid ad dictum simpliciter" meaning " from a 
 statement under a condition to a statement simply or without that condition." 
 (c.) Arguing from one special case to another special case. 
 
 b. Fallacy of the consequent, or non sequitur, where the reasoning is so loose 
 and inconsequent that no one can discover any force in it. 
 
 c. Fallacy of many questions (plures interrogationum), which results from so 
 combining two or more questions that no true answer can be given to them. 
 
 II. Logical or Formal Fallacies. 
 
 Logical fallacies are those which occur in the mere form 
 of the statement (in dictione). They may ordinarily be dis- 
 covered by the aid of the rules of deduction or the syllo- 
 gism, without any knowledge of the subject-matter of the 
 argument. They are violations of the Rules of Eeasoning 
 categorical and hypothetical. 
 
 1. Fallacies in Categorical Reasoning. 
 
 (1.) Violation of the Rules for Terms. 
 
 a. Four Terms (quaternio terminorum). Breach of Rule 1st (p. 166). 
 
 b. Undistributed Middle. Breach of Rule 2d (p. 167). 
 
 c. Illicit Process of Major or Minor. Breach of Rule 3d (p. 167). 
 
 (2.) Violation of the Rules for Premises. 
 
 a. Failure of conclusion to follow weaker part. Breach of Rule 4th (p. 168). 
 
 b. Conclusion from two negative premises. Breach of Rule 5th (p. 168). 
 
 c. Conclusion from particular premises. Breach of Rule 6th (p . 168). 
 
 d. Conclusion from particular major with negative minor. Breach of Rule 
 7th (p. 170). 
 
 2. Fallacies in Hypothetical Reasoning. 
 
 (1.) Violation of Rules for Conditionals. 
 
 Conclusion from denying antecedent or from affirming consequent. 
 Breach of Kule 2d (p. 186). 
 
 (2.) Violation of Rules for Disjunctives. 
 
 a. Confounding partitive and disjunctive judgments (p. 118). 
 
 b. Disjunctive elements not exclusive and inclusive. Breach of Rule 1st 
 (p. 188). 
 
 c. Conclusion not in accordance with the affirmation or denial of disjunction. 
 Breach of Rules 2d and 3d (pp. 188, 189). 
 
 III. Semi-Logical Fallacies. 
 
 Semi-logical fallacies are fallacies partly material and 
 partly formal. 
 
 These fallacies arise largely from the ambiguous use of terms. In 
 such cases the term used in two senses is substantially equivalent to 
 
THE UNFOLDING OF REASONING. 195 
 
 two terms. The ambiguity must first be detected by examining into 
 the meaning of the terms. The fallacy is so far material. When the 
 ambiguity is fairly detected, the fallacy is at once transformed into the 
 formal or logical fallacy of four terms. It includes : 
 
 1. Fallacy of Equivocation, consisting in the use of the 
 
 same word in two distinct senses. 
 (1.) Fallacy of ambiguous middle (p. 82). 
 (2.) Fallacy of homonymous terms (p. 83). 
 
 2. Fallacy of Amphibology, consisting in ambiguous gram- 
 matical structure of a sentence. 
 
 E. g., M The Duke yet lives that Henry shall depose." 
 
 3. Fallacy of Composition and Division, arising from using 
 a term distributively (pp. 112, 115) in one premise, and col- 
 lectively (pp. 54, 113) in the other. 
 
 This is especiaUy common in the use of " all " (p. 113), " not aU" (p. Ill), etc. 
 
 4. Fallacy of Etymology. This includes : 
 (1.) Fixing upon a wrong root (p. 76.) 
 
 (2.) Assuming that the original meaning of the root of a word de- 
 cides the present meaning of the word (p. 76). 
 
 Note.— For enumerations of the sources of human error, see Bacon's Novum 
 Organum, Lib. i. ; Mill's Logic, Book V., ch. ii. ; Hamilton's Logic, Lect. xxiii. 
 
 Praxis. — Examine the following arguments, completing them if in- 
 complete, and reducing to regular form if irregular. Examine and de- 
 fine the important conceptions or terms. Name the kind of argument 
 in each case, formulating with letters and illustrating by diagram. 
 Present the proof of the premises. Test each example by the Rules, 
 naming and explaining the fallacy, material, logical or semi-logical, 
 wherever such fallacy exists. If categorical, reduce to Fig. 1. 
 
 1. A science which furnishes the mind with a multitude of useful 
 facts deserves cultivation ; but Logic is not such a science ; .\ Logic 
 does not deserve cultivation. 
 
 2. Nuisances are punishable by law ; to keep a noisy dog is a nui- 
 sance ; .*. to keep a noisy dog is punishable by law. 
 
 3. Twice two and three are seven ; twice two and three are ten ; 
 .'. seven is equal to ten. 
 
 4. If motion is possible, a body must move either in the place where 
 it is, or in a place where it is not ; but a body cannot move in a place 
 
196 PRACTICAL LOGIC 
 
 where it is, and of course it cannot move where it is not ; .*. motion is 
 impossible. 
 
 5. What you bought yesterday you eat to-day ; you bought raw 
 meat yesterday ; .*. you eat raw meat to-day. 
 
 6. The Jews are avaricious; .*. the prophet Daniel was avaricious. 
 
 7. All bodies that move themselves are animated ; the stars move 
 themselves ; .*. the stars are animated. 
 
 8. Mouse is a syllable ; but a mouse eats cheese ; .*. a syllable eats 
 cheese. 
 
 9. If it be fated that you recover from your present disease, whether 
 you call in a doctor or not you will recover ; again, if it be fated that 
 you do not recover from your present disease, whether you call in a 
 doctor or not you will not recover ; But one or other of the contra- 
 dictories is fatal ; .'.To call in a doctor is of no consequence. 
 
 10. Episcopacy is of Scripture origin; the Church of England is 
 the only episcopal church in England; .'. the Church established is 
 the Church that should be supported. 
 
 11. Carbon is combustible ; diamonds are composed of carbon ; 
 .\ diamonds are combustible. 
 
 12. Rain has fallen, if the ground is wet ; but the ground is not 
 wet ; .*. rain has not fallen. 
 
 13. None but mortals are men ; monarchs are men ; .*. monarchs 
 are mortals. 
 
 14. Logic as it was cultivated by the Schoolmen proved a fruitless 
 study ; .*. Logic as it is cultivated at the present day must be a fruit- 
 less study. 
 
 15. Men can live without animal food, and they can live without 
 vegetable food, as has been often demonstrated ; but all food is either 
 animal or vegetable; .*. men can live without food. 
 
 16. All birds are animals ; no reptiles are birds ; .'.no reptiles are 
 animals. 
 
 17. He who is most hungry eats most ; he who eats least is most 
 hungry ; .*. he who eats least eats most. 
 
 18. If rain has fallen, the ground is wet; but rain has not fallen; 
 .'. the ground is not wet. 
 
 19. Night must be the cause of day, for it invariably precedes it. 
 
 20. If Brandreth's pills are of any value, those who take them will 
 improve in health ; my friend who has been taking them has im- 
 proved in health ; .*. they are of value. 
 
 21. He that can swim needs not despair to fly; for to swim is to fly 
 in a grosser fluid, and to fly is to swim in a subtler. 
 
THE UNFOLDING OF REASONING. 197 
 
 22. The ground is wet, if rain has fallen; the ground is wet; .\ rain 
 has fallen. 
 
 23. All stars are self-luminous ; all planets are not self-luminous ; 
 .\ no planets are stars. 
 
 24. Some flowers are tulips; all flowers are beautiful; .*. all the tu- 
 lips are beautiful. 
 
 25. The probability of the existence of a God, derived from the ex- 
 istence of the universe, may be stated as f ; from order in the universe, 
 f ; from conscience, f ; from common belief of mankind, f , etc. These 
 all fall far below unity or full proof ; .*. the proofs of the existence of 
 a God are insufficient to warrant belief. 
 
 26. If the books in the Alexandrine Library be in conformity with 
 the doctrines of the Koran, there is no need of them ; if adverse, then 
 also they should be burned. 
 
 27. If the ground is wet, rain has fallen ; but rain has fallen ; .\ the 
 ground is wet. 
 
 28. The hope of immortality is either a rational expectation or an 
 illusion ; but that belief cannot be an illusion which all the most en- 
 lightened peoples have adopted. 
 
 29. Personal deformity is an affliction of nature ; disgrace is not an 
 affliction of nature ; .'. personal deformity is not disgrace. 
 
 30. No idle person can be a successful writer of history ; .*. Hume, 
 Macaulay, Hallam, and Grote must have been industrious. 
 
 31. Bacon was a great lawyer and statesman; and as he was also 
 a philosopher, we may infer that any philosopher may be a great 
 lawyer and statesman. 
 
 32. Nothing is better than wisdom ; dry bread is better than noth- 
 ing; .*. a fortiori is dry bread better than wisdom. 
 
 33. If classical education is worth the cost, either it must be pre- 
 eminently fitted to develop the mental powers, or it must furnish ex- 
 ceedingly valuable information ; but neither alternative can be main- 
 tained, and so classical education is not worth the cost. 
 
 34. Men love to be humbugged ; the President of the Bible Society 
 is a man ; .'.he loves to be humbugged. 
 
 35. All power proceeds from will as its antecedent ; a steam-engine 
 has no will ; .*. it has no power. 
 
 36. What produces intoxication should be prohibited; the use of 
 spirituous liquors produces intoxication; .*. the use of spirituous 
 liquors should be prohibited. 
 
 37. All the trees in the park make a thick shade ; this tree is one 
 of them ; /. this tree makes a thick shade. 
 
 17* 
 
198 PRACTICAL LOGIC. 
 
 38. The object of war is durable peace ; .\ soldiers are the best 
 peacemakers. 
 
 39. Improbable events happen almost every day ; bnt what happens 
 almost every day is a very probable event ; .\ improbable events are 
 very probable events. 
 
 SUMMARY OF RESULTS. 
 
 The aim of the Logic of Reasoning is, in general, to train 
 to the best thinking and fullest appreciation of thought in its 
 third form. The perfection of thinking as reasoning depends 
 upon the degree of certainty that the right cause or mid- 
 dle term has been fixed upon. As the finished result of Con- 
 ception is clear and distinct thinking, and that of Judg- 
 ment connected thinking, so that of Reasoning is continuous 
 thinking. 
 
 The conclusions from induction are probable truths (judg- 
 ments, p. 132), varying in probability all the way from mere 
 hypotheses to perfected theories. The conclusions from 
 deduction are always certain truths (judgments, p. 132) 
 when the premises are certain and the reasonings correct, 
 and probable truths when the premises are only probable. 
 
 The special aim of the Practical Logic of Reasoning 
 should be to train the thinker to the highest degree of 
 skill and certainty in using the various processes of induc- 
 tion and deduction in his own thinking, and to the greatest 
 readiness and accuracy in grasping and testing these pro- 
 cesses and their products as they are presented in the think- 
 ing of others. 
 
Part IV. 
 
 THE LOGIC OF CONSTRUCTION OR THE SYSTEM. 
 
 The aim of the Logic of Construction, should be to train 
 the student to skill in dealing with the Fourth Form of 
 Thought. 
 
 Definition, — Construction is that higher form of thought 
 in which we combine mutually related products of the lower 
 forms of thought, according to some rational principle, into 
 one relatively complete whole (pp. 11-13). The product 
 of construction is known as the System. 
 
 Ueberweg defines system as " the orderly combination of mutually- 
 related knowledge into one relatively complete whole." System is 
 either mechanical or rational. Bational system is that in which the 
 combination is a- result of the application of some rational principle ; 
 mechanical system, that in which such rational principle is wanting. 
 
 The alphabet, as arranged in the order, a, b, c, etc., is a mechanical 
 system; as arranged in classes, — as vowels, semi- vowels, and conso- 
 nants; or tonics, subtonics, and atonies, — it is a rational system. 
 There are three forms of rational system : scientific system ; artistic 
 system ; practical system. These all imply orderly arrangement, but 
 they differ in the law by which that arrangement is effected ; that of 
 scientific system- being according to the law of the true ; that of artistic 
 system according to the law of the beautiful ; that of practical system 
 according to the law of the good. 
 
 In scientific system the aim is to combine the related thoughts in 
 
 199 
 
200 PRACTICAL LOGIC. 
 
 such a way thai the totality will exactly express the truth and the 
 whole truth. It is, therefore, said to be governed by the Law of the 
 True. In artistic or aesthetic system the aim is to combine the related 
 truths in such a way as to produce a totality which will express di- 
 versity in unity, or beauty. It is, therefore, said to be governed by 
 the Law of the Beautiful. In practical system the aim is to combine 
 forces and agencies as means so as to secure a whole by which some 
 desired end or good may be secured. It is, therefore, said to be gov- 
 erned by the Law of the Good. 
 
 Artistic or aesthetic system belongs to Esthetics ; the other forms 
 may be regarded as properly belonging to Logic (p. 12), and will be 
 briefly considered. 
 
 Constructive thinking is manifestly the highest act of the 
 human intellect, and should, therefore, be made prominent 
 in the later stages of higher education. The formation and 
 unfolding of systems will be briefly treated in successive 
 Chapters. 
 
 CHAPTER I. 
 
 THE FORMATION OP CONSTRUCTION 
 OR SYSTEM. 
 
 An understanding of the combination of mutually related 
 thoughts into systems, by the constructive faculty, must 
 prepare the way for unfolding and testing such systems. 
 The process and the products will be considered briefly 
 under each of the forms of construction. 
 
 Section I.— Scientific Construction. 
 Scientific construction is construction according to the 
 law of the true. Its product is Scientific System. 
 
 Topic First — Process of Forming and Verifying Scien- 
 tific System. 
 
 Three things are essential in thinking in the form of 
 scientific system: First, fixing upon some one sphere of 
 
THE FORMATION OF CONSTRUCTION. 201 
 
 mutually related thoughts, or thoughts constituting a whole ; 
 secondly, maintaining logical consistency in the joining of 
 all the parts under this whole ; thirdly, verifying the agree- 
 ment of the resulting combination, in its parts and as a 
 w T hole, with the entire reality of the sphere which is being 
 systematized. 
 
 These give the Laws of Scientific Construction ; the Laws 
 of Logical Unity or Logical Totality ; of Logical Consis- 
 tency ; and of Logical Truthfulness. 
 
 I. The Law of logical Unity or Totality. 
 
 The unity and totality of a system are determined by 
 this, that all the individual thoughts contained in it depend 
 on a common principle. A principle, in this sense, has been 
 defined as " an absolutely or relatively original element on 
 which a series of other elements depends." It is the unify- 
 ing thought which binds together the otherwise disconnected 
 and unorganized mass of thoughts. Hence arises 
 
 Bale 1st. — Seek a principle which will bring the thoughts to be 
 systematized into unity under one sphere or whole. 
 
 The Law of Totality may also be presented as the Law of Numer- 
 ical Completeness, which requires that a scientific view of any region 
 of fact or truth shall present all the essential facts and truths, none 
 added and none omitted. Any so-called science, e.g., astronomy, may 
 be rendered so far false by an addition to the facts or truths or sub- 
 traction from them. 
 
 Various principles, or points of view, may be made use of in system- 
 atizing any region of truth. The sphere may thus he enlarged or 
 diminished. For example, the astronomer may aim to present the 
 astronomy of the solar system or of the universe ; he may give his 
 work a mathematical or a descriptive form ; he may present the solar 
 system and universe as they are, or treat them historically, giving the 
 stages in their development. 
 
 II. The Law of Logical Consistency or Correlation. 
 
 The logical consistency of a system requires the proper 
 joining or correlation of all the parts under the whole or 
 
202 PRACTICAL LOGIC. 
 
 totality. All the truths combined should be in their proper 
 relation to each other. 
 
 The main relations to be kept in mind in snch work are those of 
 substance and properties, as brought out under Observation (p. 29) ; 
 those of content of concepts (p. 40) and extent of concepts (p. 45) ; 
 those of reason and consequent, as involved in induction and deduc- 
 tion (pp. 138-9). There should be perfect accuracy of thought in all 
 the parts and relations of the system. Hence arises 
 
 Bule 2d. — See that all the parts are properly joined or articulated 
 under the one whole. 
 
 Any science, e. g., zoology, may be rendered false by any departure 
 from the facts or laws of succession ; or from the relations of co-ordina- 
 tion, subordination, etc., brought out by logical and scientific division; 
 or from the relations of reason and consequent, as involved in induc- 
 tion and deduction. 
 
 III. The Law of Logical Truthfulness. 
 
 The logical truthfulness of a system requires that the 
 entire system so constructed shall, in all its parts and as a 
 whole, be in accordance with the reality, or the entire 
 sphere or whole which is being systematized. This con- 
 formity with . the reality is the crucial test of a system. 
 From it arises 
 
 Rule 3d. — Test the system of thought constructed by the reality 
 which it represents. 
 
 In any scientific system any want of conformity to the sphere of 
 reality renders the system so far false. Imaginary schemes, such as 
 the scheme of organized being as unfolded by Haeckel in his History 
 of Natural Evolution, have no claim to the name of scientific system. 
 
 Topic Second. — Products of Scientific Construction. 
 
 Systems, as the products of scientific construction, are 
 either absolutely or relatively complete. 
 
 Scientific System has sometimes been confounded with systems of 
 classes (p. 44), but it is manifest that these merely form one of the 
 elements used in constructing scientific systems. Science is used in 
 various senses : " exact knowledge ;" . " classified knowledge ;" etc. 
 Ueberweg defines it as a " whole of knowledge in the form of the sys- 
 
THE FORMATION OF CONSTRUCTION. 203 
 
 tern," in which sense it is substantially equivalent to scientific system. 
 According to this view, <( scientific knowledge finds its perfection in 
 the combination of thoughts, one with the other, into a whole, which 
 in its content and form represents the objective reality." "Science as 
 such has its true existence only in the systematic form." 
 
 I. Relatively Complete System. 
 
 The Sciences, as we find them, usually deal with some 
 relative whole and not with the entire universe of truth. 
 They are inductive, deductive, or mixed, according to the 
 method of thought employed. 
 
 1. The inductive sciences result from the employment of the induc- 
 tive method of thought. 
 
 The Inductive Method involves three elements: 
 
 First, The scientific investigator starts with matters of fact. 
 
 Secondly, In reaching the materials for the science, he makes use 
 of the principles of inductive reasoning chiefly. 
 
 Thirdly, These materials are given their proper systematic form by 
 the principles of scientific construction (p. 201). Its steps are, as has 
 been seen (pp. 148-9, 200-3) : exact observation, correct interpreta- 
 tion, and scientific construction. The product is a system of thought 
 wrought out from the facts. 
 
 2. The deductive sciences result from the employment of the deduc- 
 tive method of thought. 
 
 The Deductive Method involves three elements : 
 
 First, The scientific investigator starts with ideas or relations of 
 ideas. 
 
 Secondly, In gathering the materials for the science he makes use 
 of the principles of deduction chiefly. 
 
 Thirdly, These materials are given their proper systematic form by 
 the same general principles of scientific construction made use of in 
 the inductive method. 
 
 Its steps are, therefore : proper grasp of truth, or right judgments or 
 general principles ; correct unfolding of truth ; and scientific construc- 
 tion of the results. 
 
 In it induction may be used in subordination whenever matters of 
 fact are incidentally taken into account. 
 
 The product is a system of thought unfolded from fundamental 
 thoughts or truths. 
 
204 PRACTICAL LOGIC 
 
 3. The mixed sciences arise from the joint employment of the in- 
 ductive and deductive methods. This results from the presence of 
 both facts and truths, both of which need to be wrought into the sys- 
 tem. Astronomy furnishes an illustration of mixed scientific method. 
 
 II. Absolutely Complete System. 
 
 The absolutely complete science deals with all things, or 
 the universe. It aims to construct the universal scientific 
 system and the universal philosophy, both of which are in- 
 cluded under complete scientific system in the wide sense. 
 
 Herbert Spencer distinguishes between knowledge, science, and phil- 
 osophy as follows : " Knowledge of the lowest kind is ununified knowl- 
 edge ; science is partially unified knowledge ; philosophy is completely 
 unified knowledge." The distinction nsually made between science 
 and philosophy is as follows : science deals with facts and their order, 
 or with the " what; " philosophy deals with general principles and rea- 
 sons, or the "why" It is impossible, however, to have any science so 
 completely empirical as not to involve more or less of the principles 
 or reasons of things, and equally impossible to have any philosophy 
 so entirely transcendental as not to embrace a solid basis of fact or 
 reality. In the highest sense science, as scientific system, embraces 
 both facts and their reasons, both the "what" and "the why," or 
 both science proper and philosophy. 
 
 1. The Complete Science. — Great thinkers have sought to 
 construct the one universal scientific system, and with va- 
 rious success. The system of Comte may be presented as 
 one of the best. 
 
 Comte starts with the suggestion of Descartes, that " sound knowledge 
 should advance from the simpler to the more complex phenomena" In 
 this suggestion " lay the germ of a sound arrangement of the sciences, 
 which scarcely, however, seems to have begun to bear fruit before the 
 time of Ampere and Comte." Thomson, in his Laws of Thought, pp. 
 316-319, has presented the system drawn from Comte in brief form. 
 
 " Mathematics, or the science of quantity, is at once the most simple in its 
 elements and the most general in its application, entering more or less into all 
 the sciences of nature, and constituting almost the whole of that which comes 
 next it in the order of dependence. Astronomy, or the science of the heav- 
 enly bodies, is the application of mathematical truths to the laws of matter 
 and motion, matter and the motions of material bodies being the new concep- 
 
THE FORMATION OF CONSTRUCTION. 205 
 
 tion which belongs to this science. Physics, being the science, or rather group 
 of sciences, which is conversant with the general laws of the world so far as 
 they relate to beings without life or organization, would come next ; and it 
 imports, in addition to the conceptions of Astronomy, those of light, of heat, 
 of sound, of electricity, of magnetism, and many others. Chemistry would 
 rank next, which is the science of the decomposition and combinations of 
 the various substances that compose and surround the earth. Next in order 
 of complexity would rank Physiology, founded on the additional conception 
 of vegetable and animal life. To this would succeed Anthropology, or the 
 science of man's nature ; and to this Social Science, which ascertains the laws 
 that govern men when combined in cities and nations. 
 
 Each of these departments may be divided into many branches, as Physics 
 into Acoustics, Optics, Electricity, and the like ; or Social Science into Morals, 
 
 Politics, Political Economy, Law, and the like There is a 
 
 general correspondence between this classification and the order in which the 
 various objects of science came into being. The heavenly bodies were first 
 appointed their paths in the celestial spaces ; then the surface of our earth 
 was prepared for living creatures ; then they were created after their kind, 
 and man the last. The social life of man grew up last of all, when his race 
 was multiplied on the globe ; and ever as new elements appear, the conditions 
 of society are being modified even to the present time." 
 
 We are now in a position to sketch the table of the Sciences. 
 
 " Classification of the Sciences. 
 
 Group. Mode of Treatment. 
 
 1. Mathematics Theoretical. Historical. Applied. 
 
 II. Astronomy " " " 
 
 III. Physics 
 
 IV. Chemistry " u 
 
 V. Physiology " " " 
 
 VI. Anthropology " " " 
 
 VII. Social Science " " 
 
 Religious Philosophy." 
 
 2. The Complete Philosophy. — Thinkers have also aimed, 
 in dealing with the question " Why?" to construct the uni- 
 versal philosophic system, and with equally various success. 
 The common-sense philosophy may be accepted as the best. 
 
 The philosopher mnst seek to give a rational explanation of the ul- 
 timate facts to which all scientific investigation of phenomena leads. 
 These ultimate facts are three : consciousness ; the cosmos of matter 
 and spirit ; the being back of all on which all depends. A complete 
 18 
 
206 PRACTICAL LOGIC 
 
 philosophy must, therefore, have its psychological theory, its cosmo- 
 logical theory, and its ontological theory. The three are embraced in 
 
 The Common-Sense Philosophy. 
 I. Psychological Theory.. ..Consciousness is made up of two ele- 
 ments of knowledge: experience 
 and intuition. 
 II. Cosmological Theory The Cosmos is made up of two ele- 
 ments : spirit and matter. 
 
 III. Ontological Theory The Ultimate Being, or First Cause 
 
 of the Cosmos, is the infinite, per- 
 sonal Spirit, God. 
 
 Section II,— Practical Construction. 
 Practical construction is construction according to the 
 law of the good. Its product is Practical System. 
 
 Topic First. — Process of Forming and Verifying Practical 
 System. 
 
 Three things are essential to thinking in the form of prac- 
 tical construction : First, the intelligent fixing upon some 
 one complex plan or aim ; secondly, the careful preparation 
 or gathering of ideas and forces which will serve as means 
 to this end; thirdly, the best arrangement and adjustment 
 of the means to secure the end in view. These give the 
 laws of practical aim, practical adaptation, and practical 
 unity. 
 
 I. The Law of Practical Aim. 
 
 Practical aim in constructive thinking requires that the view he 
 fixed upon some beneficent, useful, rational, or moral end to be attained. 
 Hence arises 
 
 Rule 1st. — Fix upon and define clearly in the mind the end to be 
 attained. 
 
 II. The Law of Practical Adaptation. 
 
 Practical adaptation in constructive thinking requires that all the 
 material made use of be such, and only such, as is suited to secure the 
 proposed end. Hence arises 
 
THE UNFOLDING OF SYSTEMS. 207 
 
 Rule 2d. — See that the suitable means are provided for attaining 
 the proposed end. 
 
 III. The Law of Practical Unity. 
 
 Practical unity in constructive thinking requires that all the means 
 be combined, arranged, and adjusted in such system as best to secure 
 the end proposed. Hence arises 
 
 Rule 3d. — See that the means are properly correlated so as to 
 secure the proposed end. 
 
 Topic Second. — Products of Practical Construction. 
 
 The Laws of Practical Construction govern in the pro- 
 duction of all inventions, ideals, plans of life, etc. Success 
 in life depends largely upon the possession of this power in 
 proper development. 
 
 One of the highest forms of practical construction is found in oratory, 
 in which the aim is to arrange thought in such a system as shall induce 
 a change of view, of judgment, of feeling, or of purpose in an audience. 
 
 Illustrations will suggest themselves to the teacher and student. 
 For the purpose of directing in the work, a few examples will suffice. 
 
 Praxis. — Study as practical systems: 1. A steam-engine. 2. A 
 telephone. 3. A plough. 4. The speech of Daniel Webster, in the 
 trial of John Francis Knapp, for the murder of Joseph White. 5. 
 The oration of Demosthenes on the Crown. 
 
 CHAPTER II. 
 
 THE UNFOLDING AND TESTING OP SYSTEMS. 
 
 The best use of the power of construction in the work of 
 thinking requires that the thinker should be able to grasp 
 and unfold what may be contained in any system, and to 
 test such system by the principles of construction, scientific 
 and practical. 
 
 For the purposes of the brief discussion here proposed, the two forms 
 of logical system need not be separated. Two things are of prime 
 importance: first, the ascertaining of the elements of systems, and 
 secondly, the testing of systems. 
 
208 PRACTICAL LOGIC 
 
 Section L— Ascertaining the Elements. 
 The elements of any system may be learned from the 
 Laws of Construction. In unfolding scientific constructions 
 (to which attention will be confined) three things are 
 embraced : First, the grasping of the totality involved in 
 the system ; secondly, the study of the relations of the parts 
 or the articulation of the system ; thirdly, the comparison 
 of the system with the objective reality. The careful study 
 of these elements is requisite to prepare for the testing of 
 systems. 
 
 Topic First. — The Whole and its Principle. 
 
 In studying any system it is necessary first to seize upon 
 it as a whole by ascertaining the principle which unites its 
 elements. 
 
 A system is " an organized body of truth, or truths arranged under 
 one and the same idea, which idea is as the life or soul which assim- 
 ilates all those truths." In studying and unfolding any system, it is, 
 therefore, necessary to inquire first for this organic idea or principle, 
 which is the soul of the system. This holds in all three forms of sys- 
 tem, scientific, aesthetic, and practical. 
 
 Trendelenburg distinguishes " systems of arrangement," correspond- 
 ing to systems of classes (p. 47); and "systems of development," 
 corresponding to the products of scientific construction (p. 202). 
 The former arise under Conception, by Classification or Division ; the 
 latter, under Eeasoning, by Induction and Deduction. The former 
 take the form of the descriptive, classificatory, or natural history 
 sciences, — as Botany, Zoology, etc. ; the latter, of explanatory natural 
 and mental sciences, — as Physics, Chemistry, Psychology, etc. 
 
 The principle or organic idea in systems of classes, is simply the 
 principle of classification (p. 47) or division (p. 68), which has already 
 been considered. E. g., in Zoology the system of the animal kingdom 
 is a system of classes and sub-classes, based on plan of organic structure. 
 
 The principle or organic idea in the higher form of system, or sys- 
 tem in the stricter sense, is the central truth to which the inductive 
 method leads, and with which the deductive method starts out. 
 
 Accordingly, Ueberweg has said : " The principles of knowledge are of two 
 kinds, according as the individual or particular, or the universal, serves as the 
 
THE UXFOLDIXG OF SYSTEMS. 209 
 
 starting-point of knowledge. The former do not correspond to the real prin- 
 ciples, but e natural foundations of propaedeutic knowledge; the 
 latter distinctly correspond to real principles and, accordingly, form the 
 foundations of strictly scientific knowledge. 
 
 "The propaedeutic or method of investigation proceed 
 analytically to the knowledge of real principles : the purely scientific or con- 
 structive method proceeds prej :r synthetically from principles to 
 particulars or individuals. But it is "by no means always desirable, in an 
 exposition of the sciences, to thoroughly separate the analytic from the 
 synthetic elements. Both are often to be combined with each other in the 
 treatment of individual problem 
 
 The construction and value of a system will, therefore, manifestly depend, 
 in any given case, first of all. upon the correctness and completeness of the 
 principle which unites its parts into a whole. Hence, in examining systems, 
 arises 
 
 Eule 1st. — Ascertain the principle or organic idea of the system. 
 
 In a system of Ethics the idea of right or virtue is the principle. 
 In the Moral System of the universe the idea of right as embodied in 
 the control of the Moral Go~ the principle. 
 
 Topic Second. — The Articulation or Relation of the Parts. 
 
 In studying any system it is necessary, in the second place, 
 to seize upon the relations of the parts to each other. 
 
 Every truth has relation to some other. In a system the various 
 connections of related truths are brought out. Bishop Butler s; 
 in his Sermons: "A System, Economy, or lion, is a one or a 
 
 whole, made up o: yet the several parts even con- 
 
 red as a whole do not complete the idea, unless in the notion of a 
 whole yon include the relations and respects which these parts have 
 to each or": 
 
 The relations of the thoughts to each other, in any system, may in- 
 clude any or all the possible relations of conception, judgment and 
 reasoning. The aim in all systematic knowledge is " to ..mte the facta 
 of knowledge so as to see them in their several bearings.' ' Hence 
 
 Eule 2d. — See that the parts of the system are logically connected 
 throughout. 
 
 Topic Third. — The Relation to the Objective Reality. 
 
 In studying any system, it is necessary, in the third 
 place, to compare the thought-system with the reality 
 which it represents. 
 
 IS- * O 
 
210 PRACTICAL LOGIC. 
 
 "System applies not only to our knowledge, but to the objects of 
 our knowledge. Thus we speak of the planetary system, the muscu- 
 lar system, the nervous system. We believe that the order to which we 
 would reduce our ideas has a foundation in the nature of things. And 
 it is this belief that encourages us to reduce our knowledge of things 
 into systematic order." 
 
 The final test of the correctness of any system must be found, there- 
 fore, in its exact truthfulness. Hence arises 
 
 Rule 3d. — See that the system agrees exactly with the reality. 
 
 Section II.— Testing of Systems. 
 
 As the highest process in the formation of thought is the 
 construction of systems, so the highest process in the un- 
 folding of thought is the testing of systems. 
 
 The possibilities and dangers of error have been seen to be very 
 great in Conception, Judgment and Eeasoning, but they must evi- 
 dently be as much greater in Systematizing, as this form of thought 
 is higher and more difficult than the others. Mohammedanism and 
 Buddhism in religion, Epicureanism and Utilitarianism in morals, and 
 numberless other systems in all departments of thought, maintain their 
 hold upon mankind simply because of the inability of the masses of 
 mankind to ascertain their elements and put the systems themselves 
 to the test. 
 
 Some examples of the testing of systems will best illustrate the kind 
 of work to be done in order to avoid error. In a text-book of the 
 scope of the present, it is impossible to find space for presenting such 
 examples in detail. The work must, therefore, be confined to giving 
 directions, for testing systems, and referring the teacher and student 
 to examples of such testing to be found elsewhere. 
 
 Topic First. — Directions for Testing. 
 
 The first inquiry, resulting from the carrying out of Rule 
 1st, is, What is the organic thought or principle which holds 
 together the parts of the system ? 
 
 The second inquiry, resulting from Rule 2d, is, Are the 
 parts logically connected ? 
 
 The third inquiry, resulting from Rule 3d, is, Does the 
 system of thought agree with the facts or the reality ? 
 
THE UNFOLDING OF SYSTEMS. 211 
 
 Archbishop Whately has clearly marked out the course to be pur- 
 sued in testing a system of argument. We quote his directions, which 
 are as follows : 
 
 " First, then, of whatever length the reasoning may be, whether treatise, 
 chapter, or paragraph, begin with the concluding assertion,— not necessarily 
 the last sentence expressed, but the last point established,— and this, whether 
 it be formally enunciated or left to be understood. Then, tracing the reason 
 backwards, observe on what ground that assertion is made. The assertion 
 will be your Conclusion ; the ground on which it rests your Premises. The 
 whole Syllogism thus obtained may be tried by the rules of Logic. 
 
 " If no incorrectness appear in this syllogism, proceed to take the premises 
 separately, and pursue with each the same plan as with the conclusion you 
 first stated. A premise must have been used as such, either because it required 
 no proof, or because it had been proved. If it have not been proved, consider 
 whether it be so self-evident as to have needed no proof. If it have been 
 proved, you must regard it as a conclusion derived from other assertions 
 which are premises to it, so that the process with which you set out will be 
 repeated, viz., to observe on what grounds the assertion rests, to state these 
 as premises, and to apply the proper rules to the syllogism thus obtained. 
 Having satisfied yourself of the correctness of this, proceed, as before, to state 
 its premises, if needful, as conclusions derived from other assertions. And 
 thus the analysis will go on (if the whole chain of argument be correct) till 
 you arrive at the premises with which the whole commences, which of course 
 should be assertions requiring no proof; or, if the chain be anywhere faulty, 
 the analysis will proceed till you come to some proposition, either assumed as 
 self-evident though requiring proof, or incorrectly deduced from other asser- 
 tions." See Whately's Logic, pp. 418, 419. 
 
 Topic Second. — Examples Illustrative. 
 
 The teacher of Logic will be able to furnish illustrations 
 of this subject in every department of thought. 
 
 I. Familiar Subjects. 
 
 The tests should be applied first to familiar subjects. 
 These are found in the text-books of Arithmetic, Geography, 
 Physical Geography, Grammar, Ehetoric, Psychology, Ethics, 
 etc., used in the study of these various departments. 
 
 One of the most important and useful of all mental processes is that 
 of studying and grasping a science in its entirety as a system. It 
 trains all the mental faculties, — simple cognition, memory, compar- 
 ison and construction. Until a science is so grasped, it is not in any 
 proper sense mastered, since the main thing in a science is not its sep- 
 arate facts and truths, but its whole of related facts and truths. 
 
212 PRACTICAL LOGIC. 
 
 The best preparation for grasping and testing large and complex 
 systems of thought is secured, by constantly training the student to 
 analyze, outline, and test the parts and chapters of the text-books 
 used. 
 
 •II. More Difficult Subjects. 
 
 The logical training of the young is not, however, com- 
 plete until this process of testing has been extended to more 
 difficult and abstruse subjects. The following illustrations 
 of such testing, found in various works, — some of which at 
 least will be within the reach of every teacher of Logic, — 
 may be of service. The illustrations may be extended at 
 pleasure by the teacher. 
 
 1. Analysis of Part First of Paley's Evidences of Christianity. See 
 Whately's Logic, Appendix III., pp. 421-427. 
 
 2. Mill's Criticism of the Theistic Argument for a First Cause, in 
 Ttiree Essays on Religion. Criticised in Princeton Review, September, 
 1878, Article "John Stuart Mill and the Destruction of Theism." 
 
 3. Herbert Spencer's First Principles. Criticised in The Philosophy 
 of Herbert Spencer, by Professor Borden P. Bowne ; and in Mr. Spen- 
 cer s Formula of Evolution, by Malcolm Guthrie. 
 
 o:*<o 
 
 GENERAL SUMMARY. 
 
 The last aim of all training in thinking should be to pre- 
 pare for and lead to constructive thinking. The safe con- 
 duct of life, in the largest and best sense, will depend upon 
 the thinker's power to know in system, — that is. to distin- 
 guish between true systems and false systems, as presented 
 by others, and to construct true systems scientific and prac- 
 tical for himself. To help to prepare man intellectually 
 for such conduct of life should be the aim of the Practical 
 Logic of Construction. 
 
INDEX. 
 
 Absolute, terms = non-relative, 55 ; 
 being, 28. 
 
 Abstract, or abstract notion, 31. 
 
 Abstraction, 31. 
 
 Accident, separable and inseparable, 
 29. 
 
 Accidental definition = description, 
 76. 
 
 Added determinants, 126. 
 
 Additions, inference by, 126. 
 
 Adequate knowledge, 91 ; perfectly 
 and practically, 91. 
 
 A dicto secundum quid, 193. 
 
 Affirmative propositions or judg- 
 ments, 111. 
 
 Ambiguity, of terms, 82 ; of negative 
 particles, 111; of all, some, etc., 113; 
 fallacy from, 195 ; sources.of, 82. 
 
 Amphibology, fallacy of, 195. 
 
 Ampliative judgments, 99. 
 
 Analogy, 137, 158. 
 
 Analysis, logical, 58 ; two kinds, 53. 
 
 Analysis, physical, 32 ; mental, 32. 
 
 Analytic judgment, 99. 
 
 Antecedent, 117; not cause, 150. 
 
 Argument, as middle term and cause, 
 138. 
 
 Argumentum, ad ignorantiam, 181 ; ad 
 hominem, 181 ; ad judicium, 181 ; ad ver- 
 ecundiam, 181 ; a fortiori, 180. 
 
 Argumentum ex concesso, a proof 
 derived from a proposition already con- 
 ceded. 
 
 Aristotle's Dictum, 138. 
 
 Art, definition, 14. 
 
 Artificial Classification, 42, 65. 
 
 Assertion = a statement or proposi- 
 tion, affirmative or negative, 92. 
 
 Association, ambiguity from, 82. 
 
 Assumption, any proposition taken 
 for granted as the basis of an argu- 
 ment; unwarranted, 193. 
 
 Attribute, 28 ; term, 54 ; proved, 177. 
 
 Attributive, term = connotative term, 
 54; judgment, 113. 
 
 Authority, defined, 105; competency 
 of, 104 ; credibility of, 105 ; concurrence 
 of, 106. 
 
 Axioms of Logic, 18. 
 
 Baconian Method, or inductive 
 
 method, 148. 
 Barbara, Celarent, etc., 177. 
 Base, logical, 64. 
 Begging the question, 193. 
 Belief, 16 ; see Probability. 
 
 Calculation of Probabilities, 181; 
 
 overestimation in, 193. 
 Canons, of Inductive Method, 149 ; of 
 
 syllogism, 170-175. 
 Canons of Syllogism, 170. 
 Categorematic words, 54. 
 Categorical, propositions, 117; syllo- 
 gisms, 141 ; syllogisms tested, 162. 
 Categories, 27 ; Aristotle's, 30. 
 Cause, 149, 86 ; in induction, 138 ; test, 
 153 ; complex, 154 ; hypothetical, 152. 
 "Aristotle distinguished four kinds 
 of causes for the existence of a thing. 
 —1. The Material Cause, the sub- 
 stance or matter composing it; 2. 
 The Formal Cause, the pattern, type, 
 or design, according to which it is 
 shaped ; 3. The Efficient Cause, the 
 force employed in shaping it ; 4. The 
 Final Cause, the end, motive, or pur- 
 pose of the work." 
 
 213 
 
214 
 
 INDEX. 
 
 Chain syllogisms, 143. 
 
 Chance, definition, 181. 
 
 Changes, in meaning of words, 82; 
 periodic, 151. 
 
 Characteristics = marks or proper- 
 ties, 28. 
 
 Circulus, in deflniendo, 86 ; inprobando, 
 193. 
 
 Classes, single, 42 ; systems of, 42 ; ex- 
 tent of, 44; relations of, 44; distinc- 
 tions arising from, 45. 
 
 Classification, process, 41 ; rules, 42 ; 
 results, 44; special relations from, 45 ; 
 artificial and natural, 65, 42. 
 
 Clearness of knowledge, 90. 
 
 Cognition or knowing, 10. 
 
 Collective terms, 53; undistributed, 
 113. 
 
 Colligation, definition by, 79. 
 
 Comparison, faculty of, 12 ; of objects, 
 34; of notions or terms, 92; of judg- 
 ments, 134; by similar properties, 34. 
 
 Compatible terms, 55. 
 
 Complex, concept, 35 ; proposition, 119 ; 
 syllogism, 142. 
 
 Complex conceptions, development 
 of, 121. 
 
 Composition of Causes, in complex 
 cause, 154. 
 
 Composition, fallacy of, 195. 
 
 Compound, proposition, 119; syllo- 
 gism, 142. 
 
 Comprehension of terms, 39. 
 
 Concept proper, 37 ; rules for form- 
 ing, 37, 38; distinctions, 39; relation 
 to class, 47. 
 
 Conception, definition, 12, 25 ; forma- 
 tion of, 25 ; unfolding of, 56 ; elements 
 of, 26 ; proper, 34 ; products, 56 ; logical 
 quality, 90. 
 
 Conclusion, of syllogism, 138; false, 
 141, 193 ; weakened, 171 ; from plura- 
 tive judgments, 169 ; principles govern- 
 ing, 166 ; from substitutive judgments, 
 170. 
 
 Concrete terms, 53. 
 
 Concurrence, of testimony and au- 
 thority, 106. 
 
 Condition, 149. 
 
 Conditional, propositions or judg- 
 ments, 47 ; syllogisms, 145, 185. 
 
 Confusion of words, sources of, 81. 
 
 Connotation of terms, 54. 
 
 Consequence = the connection be- 
 tween the antecedent and consequent. 
 
 Consequent, reason and, 20 ; fallacy of 
 the, or non sequilur, 194 ; in conditional 
 propositions, 117 ; as effect of cause, 20. 
 
 Consilience of Inductions = " the 
 agreement of inductions derived from 
 different and independent series of 
 facts, as when we learn the motion of 
 the earth by entirely different modes of 
 observation and reasoning." — Whewell. 
 
 Consistent terms = compatible terms. 
 
 Conspectus, of relations of concepts, 
 40 ; of relations of classes, 45 ; of judg- 
 ments, 115; of grammatical proposi- 
 tions, 116 ; of opposing judgments, 131 ; 
 of figures of syllogism, 163 ; of moods, 
 176 ; of things proved by the figures, 
 177 ; of valid moods, 177 ; of fallacies, 
 191. 
 
 Construction, Logic of, 199-212. 
 
 Content, of concepts or terms, 39. 
 
 Contradiction, law of, 18; of judg- 
 ments, 129. 
 
 Contradictory, terms, 55; proposi- 
 tions, 129 ; opposition, 129. 
 
 Convergent evidence, 106. 
 
 Converse fallacy, of accident, 193. 
 
 Conversion of propositions, 126; 
 simple, 127 ; by limitation, 127 ; by con- 
 traposition, 128 ; by opposition, 128. 
 
 Convertend, 126. 
 
 Coordinate, conceptions, 44 ; proposi- 
 tions, 119. 
 
 Copula, 94. 
 
 Criterion = of truth, 15. 
 
 Cross division, 69. 
 
 Data, the facts from which a conclusion 
 is to be drawn, 147. 
 
 Declaration, 75. 
 
 Deduction and Induction, 136. 
 
 Deductive or Combined Method, 
 203. 
 
 De facto == what actually or really 
 happens, as opposed to de jure, what 
 ought to happen by law or right. 
 
 Definition, 75 ; rhetorical, 75 ; etymo- 
 logical and by word analysis, 76 ; loose, 
 77 ; logical, 75, 77 ; perfect, 78 ; of class 
 terms, 78 ; of attribute terms, 78 ; im- 
 perfect, 79 ; extended, 79 ; nominal, real 
 and genetic, 80 ; rules, 81. 
 
 Demonstrative judgments, 131. 
 
 Demonstrative, or absolutely conclu- 
 sive, proof, analytic, 101; intuitive, 
 103; indirect, 129. 
 
INDEX. 
 
 215 
 
 Denomination, or naming, 49; pro- 
 cess and modes, 49 ; rules, 50 ; products 
 of, 52. 
 
 Denotation of terms = extent, 44. 
 
 Depth of a notion ; see Content. 
 
 Description, or accidental definition, 
 76. 
 
 Destructive conditional syllo- 
 gism, 186. 
 
 Diagrams, of content, 40 ; of extent, 
 45; of opposition, 129; of syllogism, 
 167-175. 
 
 Dichotomy, 65. 
 
 Differences and resemblances, 41. 
 
 Differentia, or specific difference, 46. 
 
 Dilemma, 145; rules of, 189. 
 
 Dilemmatic, judgments, 118; syllo- 
 gisms, 145, 189. 
 
 Discovery, or investigation, method of, 
 209. 
 
 Discursive faculties, 11. 
 
 Disjunction, inference by, 128. 
 
 Disjunctive, propositions, 117 ; distin- 
 guished from partitive, 118 ; converted, 
 118; syllogisms, 145, 188. 
 
 Distinct knowledge, 90. 
 
 Distribution of terms, 111-113 ; rules, 
 115. 
 
 Division, logical, 57, 64; principle of, 
 64; forms, 65; dichotomous, 66 ; natu- 
 ral, 67 ; rules, 68. 
 
 Divisions of Logic, 22 ; principle of, 
 24. 
 
 Doubt = hesitation between various 
 views, 181. 
 
 Empirical judgments and proofs, 103. 
 
 Enthymeme, 142. 
 
 Epicbirema, 142. 
 
 Episyllogism, 142. 
 
 Equivocal terms, 82. 
 
 Equivocation, sources of, 82 ; fallacy 
 of, 195. 
 
 Essence, 29. 
 
 Essential propositions = explica- 
 tive, 99. 
 
 Euler's Notation, 45. 
 
 Evidence = any facts apprehended by 
 the mind and made the grounds of 
 knowledge and belief. As testimony 
 and authority, 103; convergent, 106. 
 
 Exceptional facts, 155. 
 
 Excluded middle, law of, 19. 
 
 Exhaustive division, 70. 
 
 Experience, 16, 103, 147. 
 
 Experimentrmn crucis, 156. 
 Experts, definition, 104. 
 Explanation of facts, in induction, 
 
 148, 155. 
 Explicative propositions, 99. 
 Extension, or extent, 44 ; relations of 
 
 to content, 48. 
 Extensive Syllogism, 163. 
 Extremes, or terms, of a proposition, 
 
 52, 94. 
 
 Fact, or phenomenon, 148. 
 
 Faculties, of intellect, 12, 72 ; discur- 
 sive, 13. 
 
 Fallacies, classification of, 191 ; in in- 
 duction, 159, 191; in deduction, 192; 
 material, 193; logical or formal, 194; 
 semi-logical, 194. 
 
 False cause, 160, 192. 
 
 Figures of speech, in definition, 87. 
 
 Figures, of the syllogism, 162; canons 
 of, 170. 
 
 Forms of thought, 11. 
 
 Fundamental principle of syllo- 
 gism, 138. 
 
 Fundamentum divisionis, or prin- 
 ciple of division, 68. 
 
 General, notion, 44; term, 53. 
 
 Generalization, 41 ; as product of in- 
 duction, 157 ; false, 159 ; mere, 154. 
 
 Genus, 46. 
 
 Grammatical combination of propo- 
 sitions, 118. 
 
 Grammatical sentences, 116; co- 
 ordination of, 119; subordination of, 
 119. 
 
 Hamiltonian Notation, 163. 
 
 Hearsay, definition and value, 104. 
 
 Homonymous terms, 83. 
 
 Hypothesis, finding the working, 147; 
 testing, 153. 
 
 Hypothetical, propositions, 117; syl- 
 logisms, 144, 185. 
 
 Identity, law of, 18 ; of concepts, 39. 
 Ignoratio Elenchi, 129, 193. 
 Illative Conversion, 126. 
 Illicit Process, of the major term, of 
 
 minor term, 167. 
 Immediate inference, 134. 
 Imperfect figures, of the syllogism, 
 
 177. 
 Imperfect induction, 157i, 
 
216 
 
 INDEX. 
 
 Inconsistent propositions = con- 
 tradictory, 129. 
 
 Inconsistent terms, or incompatible 
 terms, 55. 
 
 Indefinite use of some, 114. 
 
 Indirect demonstration, 129. 
 
 Indirect reduction, 178. 
 
 Individual, 46. 
 
 Induction, 136; unfolded, 147; pro- 
 ducts of, 157; perfect and impertect, 
 158; fallacies in, 159, 191 ; true, 156. 
 
 Inductive syllogism, 157 ; guess, 156. 
 
 Inference, mediate and immediate, 134. 
 
 Infima species, 46. 
 
 Infinitation, judgments from, 124. 
 
 Inseparable accident, 29. 
 
 Instances, exceptional, 155. 
 
 Intellect, faculties of, 13, 72. 
 
 Intension, 39. 
 
 Intensive syllogisms, 163. 
 
 Intention, first and second. " Of the 
 first intention are the names of things, 
 a man, stone, etc. ; of the second are the 
 names of names and species, as univer- 
 sal, particular, genus, species, syllogism, 
 and the like." — Hobbes. Terms of the 
 second intention express the mode in 
 which the mind regards or classifies 
 terms of the first intention. 
 
 Intuitive knowledge, 31. 
 
 Inversions restored to normal form, 
 95, 111. 
 
 Irrelevant conclusion, 193. 
 
 Judgment, definition, 12, 92; forma- 
 tion of and elements, 93 ; primitive and 
 logical, 97 ; of extent and content, 97 ; 
 impersonal, 98; verification or proof, 
 98 ; analytic and synthetic, 99 ; intui- 
 tive and empirical, 101 ; products, 110 ; 
 quality, quantity, relation, and modal- 
 ity, 110; normal forms, 114; categor- 
 ical and hypothetical, 117 ; unfolding 
 of, 121; contained, implied, and in- 
 ferred, 121 ; conversion of, 126; demon- 
 strative, assertory, and problematic, 
 131 ; of observation, 97. 
 
 Language, its relation to thought, 50 ; 
 ambiguities of, 81 ; in definition, 85. 
 
 Law, 149. 
 
 Law of thought, special and general, 
 17; fundamental, 18 ; of Identity, 18 ; 
 of Contradiction, 18 ; of Excluded Mid- 
 dle, 19 ; of Sufficient Reason, 20. 
 
 Limitation, conversion by, 127. 
 Logic, definitions, 8; practical aim, 13; 
 
 postulates, 21 ; divisions, 22. 
 Lowest species, 46. 
 
 Major term, 137 ; premise, 138. 
 
 Many questions, fallacy of, 194. 
 
 Material fallacies, 193. 
 
 Mediate inference, 134. 
 
 Members of division, 70. 
 
 Metaphysical di vision = Logical 
 Partition, 57. 
 
 Method, logical, 23. 
 
 Methods of induction, agreement, 
 149; dhTerence, 150; concomitant vari- 
 ations, 151 ; residual variations, 151. 
 
 Metonymy = transfer of meaning, 82. 
 
 Middle term, 137. 
 
 Minor term, 137 ; premise, 138. 
 
 Miracles, credible, 307. 
 
 Mnemonic verses, 177. 
 
 Modal propositions = those assert- 
 ing that the predicate does or does not 
 belong to the subject, with an intima- 
 tion of the mode or manner. 
 
 Modality of judgments, 110, 131. 
 
 Modus, ponens, 186 ; lollens, 186. 
 
 Moods of the syllogism, 164 ; valid and 
 invalid, 176. 
 
 Names or terms, notative and symbol- 
 ical, 50 ; systems of, 51 ; positive and 
 non-positive, abstract and concrete, 52 ; 
 singular and universal, 53; attribute 
 and class, connotative and non-conno- 
 tative, simple and complex, categore- 
 niatic and syn-categorematic, 54 ; rela- 
 tive and non-relative, compatible and 
 incompatible, 55 ; univocal and equiv- 
 ocal, 82 ; homonymous, 83. 
 
 Natural Classification, 65, 42. 
 
 Negation, conversion by, 128. 
 
 Negative, term, 52 ; definition, 87 ; 
 judgment, 111 ; copula, 111 ; premises, 
 168; conclusion, 166 ; testimony, 104. 
 
 Nominal definition, 80. 
 
 Non causa pro causa, 192. 
 
 Non sequitur, 194. 
 
 Notion, 39 ; simple, 31 ; identical and 
 different, congruent and conflictive, 
 contrary and contradictory, 39 ; con- 
 tent of, 39. 
 
 Novum Organum, aim of, 148. 
 
 Numerically definite, judgment, 
 114 ; syllogism, 169. 
 
INDEX. 
 
 217 
 
 Object, 28. 
 Objective, 28. 
 
 Obscure knowledge, 91. 
 
 Observation, definition, 26, 148; dis- 
 tinguished from experiment, 148 ; in- 
 struments and forms of, 26 ; objects of, 
 27 ; processes and products, 31 ; exact, 
 32 ; rules, 33. 
 
 Occasion, of an event = condition, 
 149. 
 
 Occult forms of syllogism, 143. 
 
 Opposite terms = different or con- 
 nective, 39. 
 
 Opposition of propositions, inference 
 by, 128. 
 
 Paralogism = purely logical fallacy, 
 191, 194. 
 
 Parity of reasoning, used to denote 
 that when one case has been demon- 
 strated, other similar cases can be dem- 
 onstrated by a like course of reason- 
 ing. 
 
 Particular premises, 168 ; fallacy of, 
 194. 
 
 Particular propositions, 113. 
 
 Partition = metaphysical division, 
 57. 
 
 Partition, logical, 57; matter oi, 57; 
 forms, 59 ; rules, 60 ; physical, 31. 
 
 Partitive judgments, 118. 
 
 Per accidens, conversion, 127. 
 
 Percept, 31. 
 
 Perfect figure, of the syllogism = 
 Figure I., 177. 
 
 Perfect knowledge, by conception, 
 90 ; by judgment, 131 ; by reasoning, 
 198 ; by construction, 212. 
 
 Periodic changes, 151. 
 
 Petitio principii, 193. 
 
 Phenomenon, 148. 
 
 Philosophy, definition, 204 ; complete, 
 205. 
 
 Physical definition = statement of 
 physical parts. 
 
 Plurative propositions, 114; syllo- 
 gisms, 169. 
 
 Polysyllogism, 142. 
 
 Polytomy, 68. 
 
 Porphyry, tree of, 66. 
 
 Positive terms, 52. 
 
 Post hoc, ergo propter hoc, 192. 
 
 Postulates of Logic, 21. 
 
 Predicables, 27; scheme of, 30; use 
 of, 30 ; observation of, 30. 
 19 
 
 Predicaments = Categories. 
 
 Predicate, quantified, 164. 
 
 Premise in reasoning, 138. 
 
 Principle, of division, 64 ; of system, 
 208. 
 
 Privative conception, inference by, 
 124. 
 
 Privative, terms, 52. 
 
 Probability, degrees of, 108 ; the guide 
 of life, 108; calculation of, 181 ; in in- 
 duction, 158; overestimation and un- 
 derestimation of, 193. 
 
 Problem = an assertion put forward for 
 proof or dis-proof. 
 
 Proof of judgment, 98 ; analytic, 100 ; 
 synthetic, 101; intuitive, 101; empir- 
 ical, 103; from testimony and authori- 
 ty, 103. 
 
 Proper names, 53. 
 
 Property, definition, 28; kinds, 27; 
 distinguished from attribute, quality, 
 etc., 28 ; intrinsic and extrinsic, 28 ; es- 
 sential and non-essential, 28 ; peculiar, 
 29 ; accidental, 29. 
 
 Propositions, or judgments, classifica- 
 tion of, by quality, 111; by quantity, 
 112 ; by relation, 116 ; by modality, 131 ; 
 by grammatical form, 118; by source 
 of predicate, 99. 
 
 Prosyllogism, 142. 
 
 Proximate genus, 47. 
 
 Quantification of predicate, 164. 
 Quantity of propositions, 112. 
 Quaternio terminorum, 166, 194. 
 
 Ratiocination = Syllogism or Deduc- 
 tion. 
 
 Reason = middle term, 139 ; lazy and 
 controlling, 192. 
 
 Reason and Consequent, principle 
 of, 20 ; forms of, 20. 
 
 Reasoning, logic of, 134-198. 
 
 Reductio, ad absurdum, 129, 181 ; ad 
 impossibile, 178. 
 
 Reduction, of figures, 177; of con- 
 junctive syllogisms, 187. 
 
 Relation = any connection in thought 
 or fact between things. Category or 
 properties of, 27. 
 
 Relative terms, 55. 
 
 Residues, method of, 151. 
 
 Rules, of observation, 33 ; of concept- 
 forming, 37 ; of classification, 42 ; of 
 naming, 50; of partition, 60; of divi- 
 
218 
 
 INDEX, 
 
 sion, G8 ; of definition, 81 ; of intuition, 
 102 ; of testimony and authority, 104 ; 
 of obversion, 124 ; of illative conver- 
 sion, 126 ; of illative opposition, 129 ; of 
 verifying deduction, 139 ; of induction, 
 148; of hypothesis, 153; of categorical 
 syllogism, 16G ; of sorites, 179 ; of cal- 
 culating probabilities, 182 ; of condi- 
 tional syllogism, 186; of disjunctive 
 syllogism, 188 ; of forming system, 201 ; 
 of testing system, 209. 
 
 Science, definition, 13, 204 ; complete, 
 204; practical, 14. 
 
 Semilogical fallacies, 194. 
 
 Sentence, grammatical forms, 118. 
 
 Separable accident, 29. 
 
 Signs of j udgments, universal, 113 ; 
 particular, 113 ; approximately univer- 
 sal, 114. 
 
 Similars, grasped in conception, 35. 
 
 Simple, apprehension, 31 ; conversion, 
 127. 
 
 Singular, terms, 53 ; judgments, 113. 
 
 Sophism, 191. 
 
 Sorites, or chain syllogism, 143; classi- 
 fied, 144; tested, 179. 
 
 Specialization, or deduction, 136. 
 
 Species, in Logic, 46 ; in Natural His- 
 tory, 46 ; distinctions of, 46-48. 
 
 Subaltern, genera and species, 46; 
 propositions, 129. . 
 
 Subalternans, subalternates, 129. 
 
 Subcontrary, 129. 
 
 Subject, 28; and predicate, 94 ; naked, 
 127. 
 
 Subjective, 28. 
 
 Subordinate, genera and species, 47 ; 
 propositions, 129. 
 
 Substance, definition, 28; properties 
 of, 28. 
 
 Subsumption = bringing a special case 
 under the general rule or law ex- 
 pressed in the major premise or sump- 
 tion, 192. 
 
 Sufficient Reason, law of, 20; basis 
 
 of reasoning, 138. 
 Summum genus, 46. 
 Sumption = major premise, 192. 
 Syllogism, 24, 134 ; inductive, 157. 
 Symbolical terms, 50. 
 Syncategorematic terms, 54. 
 Synthesis, or synthetic method, 209. 
 Synthetic syllogism, 134. 
 System, definition and forms, 12, 199 ; 
 
 of classes, 46 ; natural, 67. 
 
 Tacit or occult premise, 142. 
 Tautology, in definition, 86. 
 Terms, or names, formation of, 52; 
 
 classification of, 52-56 ; distribution of, 
 
 115. 
 Testimony and Authority, nature 
 
 of, 16 ; proof from and rules for, 103. 
 Theory = verified hypothesis, 148. 
 Thing, 32. 
 Thought, definition, 10 ; forms, 11 ; law, 
 
 17. 
 Transfer of meaning of terms, 82. 
 Tree of Porphyry, 66. 
 Trichotomy, 68. 
 Trilemma=dilemmatic syllogism (145) 
 
 with three alternatives. 
 Truth, definition and criterion, 15; 
 
 modes of arriving at, 16; degrees in 
 
 assurance of, 16. 
 
 Universal, terms, 53 ; propositions, 112. 
 Univocal terms, 82. 
 
 Variations, method of, 151 ; periodic, 
 151. 
 
 Weakened conclusion, 171. 
 
 Weaker part, in syllogism, 168. 
 
 Whole, kinds of, 57. 
 
 Witnesses, competency, 104; credibil- 
 ity, 105; concurrence of, 106; inci- 
 dental variations of, 106; noted liars, 
 106. 
 
Model Text-Books 
 
 FOE 
 
 t\\tmh> ^dmm> awl fylUnttt 
 
 CHASE & STUART'S CLASSICAL SERIES. 
 
 COMPRISING EDITIONS OF 
 
 Ccesar's Commentaries, 
 
 First Six Boohs of JEneid, 
 Virgil's jEneid, 
 
 Virgil's Eclogues and Georgics, 
 Cicero's Select Orations, 
 Horace's Odes, Satires, and Epistles, 
 Sallust's Catiline et Jugurtha, 
 
 Cicero De Senectute, et De Amicitia, 
 Cornelius Nepos, 
 
 Cicero De Officiis, 
 Cicero's Tusculan Disputations, 
 
 Cicero de Oratore, Juvenal, 
 
 Terence, Tacitus, 
 
 Ovid. In Preparation. Livy. 
 
A 
 
 SERIES OF TEXT-BOOKS 
 
 ON THE 
 
 ENGLISH LANGUAGE. 
 
 By JOHN S. HART, LL.D., 
 
 Late Professor of Rhetoric and of the English Language in the 
 College of New Jersey. 
 
 The Series comprises the following volumes, viz.: 
 
 Language Lessons for Beginners, 
 Elementary English Grammar, 
 English Grammar and Analysis, 
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 Composition and Rhetoric, 
 A Short Course in Literature, 
 A Class-Booh of Poetry, 
 A Manual of American Literature, 
 A Manual of English Literature. 
 
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 MODEL SERIES OF ARITHMETICS. 
 
 By EDGAR A. SINGER, A.M., 
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 The Model Primary Arithmetic, 
 Tl%e Model Elementary Arithmetic, 
 The Model Mental Arithmetic, 
 TJte Model Practical Arithmetic, 
 
 Tlxe Model Test Arithmetic. In Preparation. 
 
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Elements of Physical Geography. 
 
 By Edwin J. Houston, A.M., Prof, of Physics and Physical 
 Geography in the Central High School of Philadelphia. 
 
 Easy Lessons in Natural Philosophy, 
 
 For Children. By Prof. Edwin J. Houston, A.M. 
 
 Intermediate Lessons in Natural Philosophy. 
 
 By Prof. Edwin J. Houston, A.M. 
 
 Elements of Natural Philosophy. 
 
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 Christian Ethics ; or, The Science of the Life of 
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 A New Text-Book on Moral Science. By Bev. D. S. Gregory, 
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 Practical Logic ; or, The Art of Thinking*. 
 
 By Bev. D. S. Gregory, D.D. 
 
 Groesbeck's Practical Book-Keeping Series. 
 
 By Prof. John Groesbeck, Prin. of the Crittenden Commer- 
 cial College. In Two Volumes, viz. : 
 
 College Edition, for Commercial Schools, Colleges, &c. 
 
 School Edition, for Schools and Academies. 
 
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 The Constitution of the United States. 
 
 For Schools, with Questions under each Clause. By Prof. 
 John S. Hart, LL.D. Should be taught in every school. 
 
 An Elementary Algebra. 
 
 A Text-Book for Schools and Academies. By Joseph W. 
 Wilson, A.M., Professor of Mathematics in the Philadelphia 
 Central High School. 
 
 The Crittenden Commercial Arithmetic and 
 Business Manual. 
 
 Designed for the use of Teachers, Business Men, Academies, 
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 A Manual of Elocution. 
 
 Founded on the Philosophy of the Human Voice, with Classi- 
 fied Illustrations. By M. S. Mitchell. 
 3 
 
The Model Definer. 
 
 A Book for Beginners, containing Definitions, Etymology, and 
 Sentences as Models, exhibiting the correct use of Words. By 
 A. C. Webb. 
 
 The Model Etymology. 
 
 Containing Definitions, Etymology, Latin Derivatives, Sen- 
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 Analysis of every word which could present any difficulties to 
 the learner. By A. C. Webb. 
 
 A Manual of Etymology. 
 
 Containing Definitions, Etymology, Latin Derivatives, Greek 
 Derivatives, Sentences as Models, and Analysis. With a Key 
 containing the Analysis of every word which could present any 
 difficulties to the learner. By A. C. Webb. 
 
 The Model Speaker. 
 
 Consisting of Exercises in Prose and Poetry, Suitable for Reci- 
 tation, Declamation, Public Readings, etc. Compiled for the 
 use of Schools and Academies, by Prof. Philip Laweence. 
 
 Anatomy, Physiology, and Hygiene. 
 
 A Text-Book for Schools, Academies, Colleges, and Families. 
 By Joseph C. Maetindale, M.D. 
 
 First Lessons in Natural Philosophy. 
 
 For Beginners. By Joseph C. Maetindale, M.D. 
 
 A History of the United States. 
 
 From the Discovery of America to the present time. By 
 Joseph C. Maetindale, M.D. 
 
 The Young Student's Companion. 
 
 Or, Elementary Lessons and Exercises in Translating from 
 English into French. By M. A. LONGSTEETH. 
 
 Tables of Latin Suffixes. 
 
 Designed as an Aid to the Study of the Latin Grammar. By 
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 of Iowa. 
 
 3000 Practice Words. 
 
 By Prof. J. Willis Westlake, A.M., State Normal School, 
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 teacher wants. Handsomely bound in flexible cloth, crimson 
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In the School-Room ; 
 
 Or, Chaptees in the Philosophy of Education. Gives 
 the experience of nearly forty y ears spent in school-room work. 
 By John S. Haet, LL.D. 
 
 Meadows' Spanish and English Dictionary, 
 
 In Two Parts : I. Spanish and English ; II. English and Span- 
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 Similar to the Model School Diary, excepting that it is intended 
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 The Model Roll-Book, No. 2. 
 
 The Model Roll-Book, No. 1, is so ruled as to show at a 
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 quarterly summary, and a blank space for remarks at the end 
 of the quarter. 
 
 The Model Roll-Book, No. 2, is arranged on the same 
 general plan, as regards spacing, etc., excepting that each page 
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Manuals for Teachers. 
 
 A Series of Hand-Books comprising five volumes, which it is 
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 ence of Teaching. Printed on the best quality of calendered 
 paper and handsomely bound. 
 
 1. On the Cultivation of the Senses, 
 
 2. On the Cultivation of the Memory. 
 
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 4. On Discipline. 
 
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 Teachers and School Officers desiring information relative to 
 our publications will please address 
 
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