ax^ > ■ ^^^^■ V ^, V' ^ •^ --:.> ,xV^^ ^ .,^' y-^' ■■^- %/ ^^'^^^^ ^^' ^ .^^' Oo. ^ ,0-' ^<^^ oo^ .^^ ^^K '.S> ^ r 35582 Copyright, 1899 By the open COURT PUBLISHING COMPANY Ali rights reserved R, R. DONNELLEY & SONS COMPANY CHICAGO TO DOCTOR CHARLES FERE PHYSICIAN IN THE SALPETRIERE, BY HIS FRIEND ALFRED BINET CONTENTS. CHAPTER I. The Definition of Perception, PAGES Statement of the problem. — Ancient theory of proof. — Per- ception is produced by the cooperation of the senses and the mind. — Perception consists of an association of sensations and images. — Examples of illusions of the senses i CHAPTER n. Images. First: The definition of images. — The indifferent type. — The visual type. — The auditory type. — The motor type. Second: The physiological theory of images. — Images result from an excitation of the sensory centers of the cerebral surface layers. Third: The image compared with the consecutive sensation of sight. . . lo CHAPTER III. Reasoning in Perception. First: Properties of images associated with sensations — Experiments on hypnotic hallucination. Second: Per- ception results from an operation of synthesis. — Gen- eric perception and individual perception. — These two kinds of perception are only different phases of the same process. — Proofs drawn from hypnotic experi- ments on systematized anaesthesia. Third: Percep- tion is a reasoning. — Comparison of perception with the syllogism. — Helmholtz's opinion. — The illusion is a sophism. Fourth : To what conditions must an ex- planation of reasoning be subject? — Discussion of Mr. Spencer's theory 56 CHAPTER IV. The Mechanism of Reasoning. PAGES First : The law of fusion. — The total fusion of sensations in Weber's experiment. — The partial fusion in the zootrope. — The partial fusion of images in the cases of Henslow and of Goethe. — The partial fusion of images in the formation of general ideas. — Comparisons drawn from Gallon's generic images. — Physiological expres- sion of the law of fusion. Second: The fusion of sen- sations and of images. — Hypnagogic hallucinations.— Toxic hallucinations. — Voluntary and involuntary illu- sions. — Analysis of a simple perception. — Every per- ception is an operation in three terms. Third: Proofs drawn from complex perceptions. — New com- parison between perception and the syllogism. — Theory of three images 102 CHAPTER V. Conclusion. First : Logical reasonings have the same mechanism as perceptive reasoning. — New arrangement of the syllo- gistic propositions. Second : Reasoning compared to a supplementary sense. Third : Reasoning is the single type of all intellectual operations. Fourth : Reasoning is an organization of images. — Physiolog- ical theory of reasoning 158 CHAPTER I. THE DEFINITION OF PERCEPTION. The important modifications which were undergone some years ago by the theory of proof stated by Aristotle, and considered for two thousand years as an impregnable truth, are well known. According to the ancient logicians, a syllogism — that is, a group of three propositions, the first of which is gen- eral — constitutes a proof. In the syllogism, "All men are mortal, Paul is a man, therefore Paul is mortal," the particular conclusion that Paul, actu- ally living, is subject to death, is proved by the major "all men are mortal," because it is contained in the major. Such is the essence of proof; the particular case is considered as proved when it is contained in the general case, as a small circle within a larger circle ;* and consequently reasoning is false whenever the conclusion is not contained within the premisses. Stuart Mill was the first to show that if it were really so, if the conclusion were contained in the premisses, reasoning would be valueless, it would teach us nothing, it would not be an instrument of discovery, but a repetition under an altered form of knowledge already acquired. In other words, it would be "solemn *Euler, materializing this conception, represented the syllogism by three circles of different areas, and enclosed one within another. Lettres a une Princesse d'Allemag-ne, ciii et seq. 2 THE PSrCHOLOGT OF REASONING. trifling." The one useful operation consists in joining to one fact a second fact not contained in the first. It is admitted, however, that reasoning supplies us every day with the knowledge of new truths. We learn a new truth when we discover that Paul is mortal, and we discover it by the aid of reasoning, since, Paul being yet alive, we are unable to learn it by direct observation.* Stuart Mill has replaced the scholastic and purely nominal theory of proof by another theory which is entirely positive. He has considered it sufificient to remark that the major proposition of the peripatetic syllogism is not general, or at least that the general proposition is not the proof of the conclusion. If we are justified in affirming that Paul is mortal, it is because John, Thomas and the rest are dead; it is because all Paul's ancestors and all their contemporaries are dead. These numerous, though always particular facts are the real premisses of reasoning, the real proofs of the conclusion. So that the conclusion is not contained in the premisses; it is distinct from them and adds something more to them. This idea, wjiich is so appropriate, simple and natural, explains how reasoning constitutes a devel- opment of knowledge, since every inference leads from one particular to another and thus adds new and previously unobserved facts to facts already known. But this point of view has given rise to a problem which has not yet been stated and which '^WCi^, Logic. Cf. Taine English Positivis7n, p. 34; Brochard Logique de Stuart Mill {Reznie philoso^higjie, tome xii) and Paul Janet {ibid.) DEFINITION OF PERCEPTION. % has remained until now unsolved. How can one particular fact prove another particular fact? The old theory of the syllogism had the merit of show- ing, although by a rough simile, the manner in which the conclusion was proved. ' It was proved because it was contained in a more general truth, by a phenomenon akin to the incasement of seeds, and the whole mental effort in reasoning was engaged upon drawing, in bringing to light and extracting these conclusions from the premisses, which enclosed them like large envelopes. But as soon as the terms can no longer be considered as containing one another, and the circles of Euler cease to represent the operations of the mind, it becomes necessary to find a new theory of proof. The mental process in the case of external per- ception belongs to the class of unconscious reason- ings. But little importance need be attached to this characteristic ; for there is really only one method of reasoning, and the study of unconscious reasoning leads us to conclusions which are applicable to all kinds of ratiocination. These conclusions are: that the fundamental element of the mind is the image ; that reasoning is an organization of images, determined by the properties of the images them- selves, and that the images have merely to be brought together for them to become organized, and that reasoning follows with the inevitable necessity of a reflex. In order to demonstrate this general conclusion as clearly as possible, we shall systematically avoid all the side issues to which a subject such as this frequently gives rise. 4 THE PSrCHOLOGT OP RBASONIAG. The word perception is vague enough. Medical men usually confound perception with sensation; they say of many a patient that he has lost the perception of red or of blue, while they are really speaking of the sensation of these colours. Hume called all states of consciousness perception. In modern times, certain psychologists, M. Janet among others, defined perception as the act by which the mind distinguishes and identifies sensa- tions. We shall adopt in this book the definition given by English psychologists* and we shall des- ignate as perception the act which takes place when our mind enters into relation with external and present objects. Perception is, from the common-sense point of view, a simple act ; it is a passive state, a kind of receptivity. To perceive an external object, our hand for example, is simply to be conscious of the sensations which the object produces on our organs. Some examples will, however, suffice to show that in every act of perception, the mind con- stantly adds to the impressions of the senses. Everybody knows that we can hear the words of a familiar song clearly, while we are frequently unable to distinguish those of an unknown song, even when both songs are sung by the same voice, a fact which plainly shows the share due to the mind. Instead of our seeking examples, proofs may be produced. Wundt and his pupils have made several experi- ments on this subject. An unknown sketch, an engraving, is illumined by a series of electric sparks, *Bain, The Emotions and The Will, p. 5S3. DEFINITION OF PERCEPTION. 5 and it is noted that the perception of this sketch, while very much confused during the first sparks, becomes more and more distinct. The impression produced on the retina is nevertheless the same at each flash; but the perception becomes each time more complete and precise, by the help of the recollection formed in the mind by the preceding perceptions.* One might add some more examples drawn from the perception of space, the complex and secondary character of which has been known to us since the days of Berkeley. Perception is therefore a mixed state, a cerebro- sensory phenomenon produced by an action on the senses and a reaction of the brain. It may be com- pared to a reflex, the centrifugal period of which, instead of manifesting itself externally in move- ments, would be expended internally in awakening associations of ideas. The discharge follows a mental channel instead of a motor one. But psychology demands a larger measure of precision. It is not enough to say that in every perception there are sensations and something more which the mind adds to the sensations. What is the nature of this addition? This question may be best answered by the study of the illusions of the senses. It is now known that in such illusions the error is not to be imputed to the sensitive organ, as the ancients believed, but to the mind. An illusion is a mixed phenomenon, composed, like the sen- sory perception of which it is a counterfeit, by the co-operation of the senses and the mind. The *Experiments cited by M. Lachelier {Revue i>hilosoi>hique, February 1885.) 6 THE PSrCHOLOGT OF REASONING. sensory impressions are always what they ought to be, the nature of the external excitant and the state of the sensitive organ being given. The error lies in the co-operation of the mind, in the interpreta- tion of the sensations. Now, the examination of some illusions will be sufificient to show in what this co-operation of the mind consists, and what is to be understood by an interpretation of sensations. One of my friends, now a university professor, has related to me this story of his youth. One evening, when he was walking alone in a country broken up by large woods, he perceived, in a clear- ing, a large fire lighted. Then, immediately after, he saw an encampment of gypsies around this fire. There they were, with their bronzed faces, lying on the ground and engaged in cooking. The night was dark, and the place very lonely. Our young man was afraid, he lost his head completely, and, brandishing the stick he held in his hand, he dashed furiously into the gypsies' camp. A moment after he was in the middle of a pond, convulsively clasping a tree-trunk with his arms, and feeling the chill of water which rose as far as his knees. Then he saw a will-o'-the-wisp flickering on the surface of the pond ; it was this shining spot which had been the starting point of his sensory illusion. I owe the following account to another of my friends. Dr. G. A. One day when he was ascending the Rue Monsieur-le-Prince in Paris, he thought he read on the glass door of a restaurant the two words verhascum thapsus. This is the scientific name for one of the scrophulariacese of our country, DEFINITION OF PERCEPTION. 7 which is commonly called ''bouillon blanc." My friend had passed the preceding days in preparing for an examination in natural history ; his memory was still surcharged with all those Latin names which render the study of botany so tiresome. Surprised at the inscription which he had just per- ceived, he retraced his steps in order to verify its accuracy, and then he saw that the tariff of the restaurant bore the simple word "bouillon." This word had suggested "bouillon blanc" to his mind, and this in turn had suggested verbasciim tJiapsus. These are two cases in point. They show us the composition of the element which the mind adds to sensation in the perception of external objects. This element must bear a remarkable resemblance to sensations, since it is indistinguishable from them. The young man who traverses a forest really believes that he sees before him a band of gypsies; all this phantasmagoria comes from a brain rendered delirious by fea. ; it is a psycholog- ical phenomenon which, whatever its nature, is very nearly related to sensation, since it does duty for it. Similarly Dr. A. believes he sees written on the door of a restaurant words which exist only in his mind ; for this confusion to be possible it is necessary once again that the mind should have the power of producing, of manufacturing and of objec- tivizing certain simulacra which in a striking manner resemble sensations. For several years past these pseudo-sensations have attracted the special attention of psycholo- gists. They are called representations in Germany, S THE PSrCHOLOGT OF REASONING. In France the prevailing term is images; it is this which we shall use. A definition of sensory perception will form the conclusion of this short introduction : Perception is the process by which the mind completes, with the accompaniment of images, an impression of the senses. We shall begin by studying these images. Their role is of the greatest importance ; in many cases they almost entirely efface the consciousness of the sensations which have given rise to them. It is this fact which justified Helmholtz in comparing the perception of external objects to an interpretation of signs. The sensations are the signs; our mind takes no more note of them than is necessary to learn their meaning. The perception of the exter- nal world is like the reading of a book; pre-occu- pied by the meaning, the reader forgets the written characters immediately after they are seen. This neglect of the sensations is proved by several inter- esting examples. We usually see trees and distant forests in green, with the lines of the hills in gray- blue; the gray-blue is to us the colour of distances. But if, altering the conditions of observation, we view the landscape from beneath our arms or be- tween our legs, the colours immediately lose their relations with the distances of the objects; they appear pure, with their true shades. We then recognize that the gray-blue of the distances is often a fairly deep violet, that the green of the vegetation shades off imperceptibly into this violet through a DEFINITION OF PERCEPTION. 9 greenish blue, and so on. (Helmholtz.) The dif- ference arises from the fact that, under these con- ditions, the sensations are valued as such, and not as signs, which are merely important because of the images which they excite. Let us proceed to the study of these images. CHAPTER II. IMAGES. We do not here intend to give a complete theory of Images; such an attempt seems premature. The question is not, in several respects, mature. But we are obliged to devote several pages to the study of these interesting phenomena; for the knowledge of the nature of images cannot fail to throw light upon the problem of the mechanism of reasoning. In short, images, along with sensations, constitute the materials of all intellectual operations; memory, rea- soning, imagination are acts which consist, in an ulti mate analysis, of grouping and co-ordinating images, in apprehending the relations already formed be- tween them, and in reuniting them into new rela- tions. ' 'Just as the body is a polypus of cells, ' ' said M. Taine, "the mind is a polypus of images." It is not long since an apparent agreement was reached regarding the psychological nature of images. Some ancient authors, it is true, had already seen what has escaped a number of our con- temporaries. Aristotle said that one could not think without a sensible image. But many intelli- gent minds were loath to admit that material signs were essential to the exercise of thought. This seemed to them to be a concession to materialism. IMAGES. II In 1865, at the time when a great discussion on hallucinations was taking place among the members of the "Societe medico-psychologique," the phi- losopher Garnier and some eminent alienists, such as Baillarger, Sandras and others, still held that an im- passable chasm separates the conception of an object which is absent or imaginary — ^otherwise called an image — and the actual sensation produced by a present object; that the two phenomena differ not only in degree, but in kind, and that they resemble each other no more than "the body and the shadow." It is interesting to compare the opinion of these writers with the replies which Galton obtained previously from a large number of scientific men, when he began his great inquiry into Mental Images (Mental Imagery). He asked, in a question- naire which he circulated, whether one was able to represent absent objects mentally by a kind of internal vision — he took a thoroughly English ex- ample : the appearance of breakfast when served — and if this entirely subjective representation had common characteristics with the external vision. While uneducated people, women, furnished him with very interesting replies on the nature of mental vision, the scientific men to whom he appealed refused to believe in this faculty, which seemed to them to be merely a figure of speech. Things have changed since that time. Psy- chologists and physiologists — notably M. Taine and Mr. Galton* — have endeavored to determine the *Taine, On Intelligetice, Part i, book II; Galton, Inquiries into Human Faculty and its Development, p. 83. 13 THE PSrCHOLOGT OF REASONING. nature of images, their seat in the brain, and their relations with sensations. They have shown that each image is a sensation spontaneously revived, generally simpler and more feeble than the original impression, but capable of acquiring, under given conditions, an intensity so great as to make us be- lieve that the external object is still seen. The complete demonstration of these truths, which now- adays have finally become trite, will be found in special works ; they are now only useful in filling out second-rate psychological treatises. We may remark in passing that this theory of the image is in no way materialistic ; it connects the image with the sensation, making the former a pre- served and reproduced sensation. Now, what is a sensation? It is not a material fact; it is a con- scious state, like an emotion or a desire. If one is tempted to see a material fact in the sensation, it is because it has a very apparent physiological correl- ative, the excitation produced by the exterior object upon the organ of the senses and transmitted to the brain. But it is known that all mental phenomena are accompanied by a physiological phenomenon. That is the law. The sensation and the image do not differ in this respect from other states of consciousness. The development of images is very variable. It varies, according to Galton, with race. The French, he says, appear to possess this gift, as attested by their talent for organizing ceremonies and fetes, their aptitude for strategy, and the IMAGES. 13 clearness of their language ; figure s-voits is an ex- pression which is often met with in French. Age and sex appear likewise to be of importance. The power of visualizing is more developed among chil- dren than among adults, among women than among men. There are probably some children, says Galton, who pass years of difficulty in distinguishing between the objective and the subjective world — that is to say, between sensations and images. But it is important, first of all, to distinguish the different kinds of images, which are as numerous as the different kinds of sensations. Each sense has its images, these being therefore visual, auditory, tactile, motor, etc. We are able, when we exercise our memory on an object, to cumulatively employ every kind of image, or to have recourse to only a single kind. Every person has his own habits, depending on the nature of his organism. We must therefore distinguish several varieties of individuals, several types.* Common experience made this distinction long ago as far as memory is concerned ; it is recognized that there is often, in the same man, a natural inequality in the different forms of memory ; a certain person recollects sounds best of all, another colours, a third figures and dates, etc. Pathology has proved the independence of these partial memories, showing that some may disappear and leave the others intact. Thus it is that a man may lose the single memory for words, or forget a single language, or be deprived solely of *The idea of distinguishing several sensory types is due to M. Charcot, who has explained it in his lectures on Aphasia, at the Salpetriere. 14 THE PSrCHOLOGT OF REASONING. his musical memory, etc. M. Ribot has made a very complete study of these partial amnesias. We are thus prepared to study the sensory types. It m.ust be understood that this inequality of the kinds of memory depends upon a more gen- eral cause, the inequality of the kinds of images; that those individuals who have, for example, a good visual memory, are those in whom visual images predominate; that consequently it is not merely the visual memory that is most conspicu- ous in them, it is also the visual reasoning, the visual imagination, etc. One may call these people visuels. There are thus several types, characterized by the predominance of one order of images in the mental routine. One of the most common types is certainly the indifferent type. In those who belong to this class no one kind of imiage is more developed than the others. When they wish to recall a person, they see in their minds the form and colour of his figure as clearly as they hear the sound of his voice. The visual memory is equal to the auditory memory; these two memories may besides be very well de- veloped, or may have remained rudimentary, but in every case they are of equal value. The indifferent also, in his reasonings, in his imaginings, in his dreams, employs the different kinds of images in equal proportions. This is perhaps the most frequent type ; it is the normal type, the approach to which must be expected, since it infers a harmonious development of all the sensory functions. Alongside the indifferent type must be placed the IMAGES. 15 visual type, which is also very common. A large number of persons make use almost exclusively of visual images ; if, for example, they think of a friend, they see his figure, but do not hear his voice; when they wish to learn a page of a book by heart, they impress upon their memory the visual image of the page with its characters, and in reciting it by heart they have this image before their mind's eye, and read it. When they recall an air, they see distinctly, by the same process, the notes of the score. But it is not only their memory which is visual; all their other faculties are. When they reason, or when they exercise their imagina- tion, they employ visual images alone. The exclu- sive development of the mind in a single sense per- mits the visuel to perform operations which are feats of skill. There are chess players who, with their eyes shut and their head turned to the wall, carry on a game of chess. It is clear, says M. Taine, that at each move the appearance of the whole chess board, with the arrangement of the various pieces, is present to them as in an internal mirror; otherwise they would be unable to foresee the consequences of the move which has been made against them and the move which they wish to make. Two friends who possessed this faculty often played mental chess games together while walking on the quays and in the streets. Galton tells us that a person of his acquaintance was in the habit of calculating with an imaginary calculating rule, the several parts of which he read mentally according as they were necessary for each of his l6 THE PSTCHOLOGT OF REASONING. problems. Many orators have their manuscript placed mentally before their eyes when they speak in public. Certain painters, designers and sculptors, after they have attentively studied a model, are able to make a copy of it from memory. Horace Vernet and Gustave Dor6 possessed this faculty. A painter once copied from memory a Martyre de Saint-Pierre by Rubens with an accuracy which deceived the connoisseurs. An English painter, mentioned by Wigan, painted a portrait standing, after only one sitting from the model. He held the man in his mind, placed him mentally on the chair, and every time that he looked at the chair he saw the person seated. Little by little his mind became confused ; he alarmed that the model had actually sat, and finally he became insane. Such is the danger of this hypertrophy of the visual image. Those who possess such an intense visualization are half under the influence of halluci- nation, and it is a hundred to one that the halluci- nation will some day become complete. We may acid that very probably visiiels are specially predis- posed to hallucinations of the sight, and conse- quently to the forms of delirium of which visual hallucinations are the symptom. According to this theory, a pure visiiel can never become q. persecute, because in the persecution delirium only the hallu- cinations of hearing are, in general, according to Lasegue's observation, met with. The perseciitd does not see his persecutors, he merely affects to hear them. We shall see later that there is an objective sign whereby we may recognize whether IMAGES. 17 an individual does or does not belong to the visual type. Persons who belong to the pure visual type are exposed, besides, to a serious danger; when they happen to lose, by one of those accidents which pathologists are at present earnestly studying, their faculty of mental vision, they lose everything at the same time. It is impossible, or at least extremely difficult, for them to make use of the other images, which have remained in a rudimentary state. The indifferent type is much better situated ; what is lost on the score of sight, for example, is regained on the score of hearing; substitutions are made be- tween the different kinds of images. M. Charcot has related, in one of his clinical lectures, an interesting pathological case, bringing to light the existence of the visual type and show- ing the kind of disorder which occurs among these subjects when they lose their faculty of mental vision. We reproduce, with a little abridgment, the observation published by M. Bernard {Pj-ogres medical, July 21, 1883). "M. X., a merchant at A , was born at Vienna; he is a very well educated man; he knows German, Spanish and French perfectly, as well as Latin and Greek classics. Until the beginning of the affection which brought him to Professor Char- cot, he read the works of Homer at sight. He knew the first book of the Iliad well enough not to hesitate in continuing a passage the first verse of which had been said before him. ''His father, professor of Oriental languages at 1 8 THE PSrCHOLOGT OF REASONING. L , likewise possessed one of the most remark- able of memories. It was the same with his brother, professor of law at W , with one of his sisters, a distinguished painter; his own son, aged seven years, already knows the most insignificant historical dates wonderfully well. "M. X. enjoyed until a year ago an equally remarkable memory. Like that of his father and of his son, it was principally a visual memory. His mental vision gave him, as soon as he wished, the representation of the features of persons, the form and the colour of things with as much distinctness and intensity, he asserts, as the reality itself. "If he were looking for a fact, a number men- tioned in his voluminous correspondence, which was written in several languages, he found them again immediately in the letters themselves, which appeared to him in their exact purport, with the smallest details, irregularities and erasures in their wording. "When he repeated a lesson at school, or a piece from a favorite author later, two or three readings had fixed the page in his memory with its lines and its letters, and he repeated it while mentally reading the desired passage, which, as soon as he wished, appeared before him with great distinctness. "M. X. has traveled much. He was fond of sketching the landscapes and views which had struck him. He drew fairly well. His memory gave him, whenever he wished, the most accurate panoramas. If he wished to recollect a conversa- tion, to bring back a speech or a spoken word, the IMAGES. 19 place of the conversation, the physiognomy of the speaker, in a word, the whole scene, a detail of which was all he sought, appeared to him in its entirety. " M. X. 's auditory memory was always wanting, or at least it never appeared to be other than a second- ary matter with him. He has never had, among others, any taste for music. "A year and a half ago he became worried about some important debts the payment of which seemed uncertain to him. He lost his appetite and his sleep ; his fears were not justified by the event. But the emotion had been so intense that it did not subside, as he hoped, and one day M. X. was suddenly startled to find that he had considerably changed. At first there was complete disorder; there was thereafter a strong contrast between his new state and the old. For a while M. X. believed that he was threatened with insanity, so many things around him seemed new and strange. He had become nerv- ous and irritable. The visual memory of forms and colours had in every case, as he was not slow to per- ceive, completely disappeared, and this knowledge had the effect of reassuring him on his mental con- dition. He found, besides, little by little, that he was able, by employing other forms of memory, to continue to successfully direct his commercial affairs. He has now resigned himself to the new situation, the difference between which and M. X.'s original situation, described above, may be readily shown. "Every time M. X. returns to A , which he frequently leaves on business, it seems to him that he is entering" an unknown town. He looks at the 20 THE PSrCHOLOGT OF REASONING. monuments, streets and houses with astonishment, as when he arrived there for the first time. Paris, which he has frequented as often, produces in him the same effect. Memory returns, however, httle by little, and at last he again discovers, readily enough, his route in the labyrinth of streets. When asked to give the description of the principal square in A , of its arcades, of its statues, he says: 'I know that that exists, but I can imagine nothing of it, and can tell you nothing about it.' He had often before drawn the roadstead of A ; now he vainly tries to reproduce the principal lines, which completely escape him. "His visual memory of his wife and children is powerless. He recognizes them at first no better than he does the roadstead and streets of A , and even by the time when, in their presence, he succeeds in doing so, he seems to see new traits and new characteristics in their physiognomy. ''He does not go so far as to forget his own per- son. Recently, in a public gallery, he found him- self barring the passage of a person to whom he was about to make his apologies, and who was only his own image reflected by a mirror. ''During our conversation, M. X. complained strongly of several returns of the visual loss of col- ours. He seemed more concerned about this than about the rest. 'My wife has black hair; I am perfectly sure of that. It is a complete impossibil- ity for me to find that colour again in my memory, as complete as that of imagining her person and her features.' IMAGES. 21 "This visual amnesia also extends to the things of childhood as well as to more recent things. M. X. no longer knows anything visually of the pater- nal mansion. This memory was formerly very near to him, and he evoked it often. "The examination of the eye gave completely negative results. M. X. suffers from a myopia as strong as -/D. Here is also the result of the ex- amination of M. X.'s ocular functions made with the greatest care by Dr. Parinaud, in the ophthalmic room at the hospital: No ocular lesions or func- tional troubles objectively apparent, if there be not always a slight enfeeblement of the chromatic sensi- bility, affecting all colours equally. "We may add that no somatic symptoms pre- ceded, accompanied or followed this loss of the visual memory observed in our patient. "M. X. is now obliged, like almost everybody else, to open the copies of his letters so as to find the information he wants there; and he must, like all the world, peruse them before he comes to the place he is looking for. "He recollects no more than a few of the first verses of the Iliad, and in the reading of Homer, Virgil or Horace he no more than begins, so to speak, to feel his way. ""He utters, half -aloud, the figures which he is adding, and he is no longer able to proceed save by small partial calculations. "When he recalls a conversation, when he wishes to recollect a thing said in his presence, he plainly feels that he must now, and not without 22 THE PSl'CHOLOGT OF REASONING. effort, consult his auditory memory. The words, the recollected speeches., seem to hivi to resound in his ear, a sensation which is quite nezv to him. "Since this great change occurred in him M. X. has been obliged, in order to learn anything by heart, a series of phrases for example, to read these phrases aloud several times, and thus influence his ear, and later, when he repeats the thing he has learned he has a very clear sensation of internal hearing preceding the delivery of the words, a sensation which was previously unknown to him.* "An interesting detail is that, in his dreams M. X. no longer has, as before, the visual representa- tion of things. The representation of words alone remains to him, and these belong almost exclusively to the Spanish language." The auditory type seems to us to be rarer than the preceding types; it is recognized by the same distinctive characteristics. Persons of this type conceive all their recollections in the language of sound; in order to recall a passage they impress upon their minds, not the visual aspect of the page, but the sound of their words. Reasoning is with them auditory, as is memory; for example, when they perform a mental addition, they verbally repeat the names of the figures, and in some way add the sounds, without having a representation of the written sign. Their imagination also takes an auditory form. "When I write a scene," said Legouve to Scribe, "/ hear; you see; at each *I am now obliged, writes M. X. . . to say to myself the things which I ■wish to retain in 7ny memory, -while formerly I had merely to ^hotogra^ih them by my sight. IMAGES. 23 phrase which I write, the voice of the person who is speaking strikes my ear. You, who are the theatre itself,' your actors walk, act before your eyes; I am the listener and you the spectator.''' "Nothing could be more correct, ' ' said Scribe. * ' Do you know where I am when I write a piece? In the middle of the parterre." (Cited by Bernard in De Vaphasie, p. 50.) It is plain that the/^/r^ auditif, seeking to develop only one of his faculties, is capa- ble of accomplishing, like the visuel, regular feats of memory ; for example, Mozart noting down from memory, after two hearings, the Miserere of the Sixtine Chapel; deaf Beethoven composing huge symphonies and repeating them to himself inter- nally. By way of compensation, the auditif, like the visuel, is exposed to serious dangers ; for if he lose his auditory images, he is left resourceless; he is completely bankrupt. It is possible that those who are subject to hallu- cinations of the hearing and those individuals who are attacked by the delirium of persecution belong to the auditory type ; and that the predominance of one order of images creates a predisposition to a corresponding order of hallucinations — and perhaps also of delirium. We have yet to speak of the motor type, which is perhaps the most interesting of all, and by far the least known. People who belong to this type, the inoteurs, as they are called, make use of, in memory, reasoning and all their other intellectual operations, images derived from movement. To fully under- stand this important point, it will be sufficient to 24 THE PSrCHOLOGT OF REASONING. remember that all "our perceptions, in particular the important ones, those of sight and touch, imply- as integral elements movements of the eye or the members; and that if movement is an essential element when we see an object really, it must play the same role when we see it ideally."* For exam- ple, the complex impression of a ball, which is there in our hand, is the resultant of optical impressions of the eye, impressions of touch, of muscular adjustments of the eye, of movements of the fingers, and of the muscular sensations which result there- from. f When we think of the ball, this idea must comprise the images of these muscular sensations^ as it comprises the images of the sensations of sight and of touch. Such is the motor image. That its existence was not earlier recognized is due to our knowledge of the muscular sense being compara- tively recent ; it was never discussed in ancient psychology, where the number of the senses was reduced to five. There are people who remember a drawing bet- ter when they have followed the outlines with their finger. Lecoq de Boisbaudran made use of this means in his teaching of art, in order to accustom his pupils to draw from memory ; he made them follow the outlines of the figures with a pencil held at a distance in the hand, thus obliging them to associate the muscular with the visual memory. Galton relates a curious corroborative fact: "Colo- *Ribot, The Diseases of the Will, p. 5. (Chicago: The Open Court Pub. Co.) tW. James has shown that these muscular sensations are the afferent sensations which proceed from contracted muscles, stretched ligaments, compressed articulations, etc. The Feeling of Ejfort, Boston, 1880. IMAGES. 25 nel Moncrieff, " he says, "informs me that young Indians occasionally came to his quarters, and that he found them much interested in any pictures or prints that were put before them. On one of these occasions he saw an Indian tracing the outline of a print from the Illustrated News very carefully with the point of his knife. The reason that he gave for this odd manoeuvre was that he would remember the better how to carve it when he returned home."* In this case the motor image of the movements was intended to reinforce the visual image; this young savage was a niotetir. Should this process not be generalized and ap- plied to education? It is probable that a child would learn to read and write more quickly if he were trained to trace the characters at the same time as they were spelt. The belief that it is impossible to do two things well at the same time is a prejudice. By making reading and writing proceed together, the two memories, visual and motor, are constrained to associate and to aid one another like two horses harnessed to the same carriage. The motor image enters as an essential element into a large number of mental combinations, although its presence is often unsuspected. The memory of a movement is based upon motor images; when these images are destroyed, the memory of the movement is lost, and, which is more curious, in certain cases even the aptitude to execute it. Pathology supplies us with several ex- amples of this, in motor aphasia, in agraphia, etc. *Galton, Inquiries into Human Faculty and its Development, p. 106. 26 THE PSl'CHOLOGT OF REASONING. Let us take the case of agraphia. An educated man, knowing how to write, loses all at once, suddenly, as a result of cerebral accidents, the faculty of writ- ing; his arm and his hand are in no way paralyzed, and yet he is unable to write. Upon what does this powerlessness depend? He himself says: upon his no longer knowing. He has forgotten how he must proceed in order to trace the letters, he has lost the memory of the movements to be executed, he no longer possesses the motor images which when formerly he set himself to write directed his hand. It is possible, thanks to hynotism, to vary the examples of these systematized paralyses, which affect only a particular system of movements, leav- ing the others intact and the arm completely free. It is in this way that we may make a hypnotized subject lose, by suggestion, the faculty of accomp- lishing a definite act, such as smoking, sewing, embroidering, laughing, etc. We have often in- sisted on the advantage which hypnotism offers in this respect, in the study of the majority of motor and sensitive troubles. * Other patients, struck by verbal blindness, make accurate use of these motor images in order to make up for what they lack in another way. We collect all these examples because the subject is not popular- ly known ; it will be useful if we combine several facts scattered here and there, and endeavour to make a synthesis of them. An individual afflicted by ver- bal blindness is no longer able to succeed in reading the characters placed before his eyes, although his *Binet,and Fere, Les para lysies par suggestion {Revtie scieniifique,]\x\y. IMAGES. 27 vision may be intact or sufficiently good to permit of perusal. The loss of the faculty of reading is sometimes the only trouble which exists at a certain time ; the patient who is thus maimed may, how- ever, succeed in reading, but indirectly, by means of a roundabout method which he often discovers for himself; all he has to do, in order to understand the meaning of the characters, is to trace them with his finger. What happens in a case such as this? By what mechanism can he establish a substitution between the eye and the hand? The motor image gives us the key to the problem. That the patient is able to read, in some way, with his fingers, is because he receives, in describing the characters, a certain number of muscular impressions which are those of writing. We may say at a stretch, the patient reads while writing (Charcot) ; that is, the graphic motor image suggests the meaning of the characters according to the same standard as the visual image. We have just seen the place which the motor image occupies in the sphere of sight and in the sphere of movement. Its role is no less important in the sphere of hearing. There are persons in whom the mental representation of a sound is always a motor image of articulation. M. Strieker is one of the number. He it is who was the first to make the particulars of this subject known. The follov/ing are the principal proofs he has employed : "When I form," he says, "the image of the letter P, the same sensation is produced in my lips as if I were reallv about to articulate it. If I think of the 28 THE PSYCHOLOGT OF REASONING. letter R, I experience the same sensation at the base of the tongue as if I expressly wished to utter that consonant. In my opinion, this sensation constitutes the essence of the image of sound." Such is the first proof; the second is that it is im- possible to imagine a letter at the same time as the muscles used in articulating it are given a fixed position which prevents them from entering into action. One cannot think of the letter B, which is a labial, while the mouth is held wide open, a position Avhich hinders the movement of the lips. Finally, the third proof is that one cannot have at one and the same time the representation of two letters, A and U for examiple, when the muscles which are employed in articulating them are the same. ''Whoever," he says, "is capable of simul- taneously producing, by constraining his breathing for a sufficient interval, the sounds A and U, is justified in regarding my theory as null and void. I need do no more than appeal to the judgment of the reader. Such a simultaneity is absolutely impossible, since the very muscles employed in the formation of the auditory image of A must also be used in forming that of U. Now, I could not innervate them simultaneously — as would neverthe- less be necessary — in one manner for the sound A and in another manner for the sound U." To make this quite clear, it must be remarked that M. Strieker's experiments are in no way con- cerned with the visual image of letters ; it is evident, for example, that one may graphically represent to one's self the letter B while the mouth is kept open; IMAGES. 29 but that is not the question. M. Strieker meant, by the representation of a letter, tlie auditory rep- resentation alone, that which constitutes internal speech. This author maintains that what is taken to be an auditory image, that is to say, an enfee- bled repetition of the sound which is heard when a given letter is pronounced, has nothing to do with the sense of hearing; it is a motor image, a beginning of an articulation which stops before reaching its end. Objections have been raised to M. Strieker's work by M. Paulhan, who entirely disputes the facts advanced. M. Paulhan has performed all the experimenta cruets laid down by M. Strieker, and he states that he can do a large number of the things which M, Strieker declares to be impossible. "I find," he says, "that I am able, w\\i\Q pi'onotnicing the letter A aloud, to represent to myself mentally the series of vowels, and even to imagine an entire phrase ; I conclude from this that, since under these conditions — that is to say, the muscles used in pro- nouncing A being innervated — the motor image of the other vowels cannot be produced, I conclude from this, I say, that the image of the other vowels and of the other words is not, at least for me and those who feel like me, a motor image." What does this difference of opinion prove? Simply that the two observers have different images and belong to different types. M. Strieker belongs, for a certainty, to the motor type ; he is so to this degree that he does not even conceive that others might be constituted differently. It is by virtue of the exaggeration, the abnormality which the phe- So THE PSrCHOLOGT OF REASONING. nomenon presents in him, that he has discovered a fact which no one had noticed. But as we have always the defects of our quahties , M. Strieker completely ignores the role which sight and hearing play in the recollection of words, and he attributes everything to the motor image. He even goes as far as to make this astonishing observation : "I have not yet met any one who could have said to me that he imagined the contents of a newspaper article with the printed characters which composed it. One may remember several articles by heart, several phrases, but as words which are pronounced internally, and not as graphic images of words which might be read in the memory, as on the printed page." It would be difficult, one will admit, to write anything more false. All the visiLels, and they are many, do what M. Strieker declares to be impossible. This is a good illustra- tion of the remark that everybody, in philosophiz- ing, gives us the theory of his own nature. On the other hand, it is probable that M. Paul- han and those who feel like him belong to the purely auditory or the indifferent type. Such is the very simple solution which may reasonably be given to this httle debate.* II. The theory of the Image was at the point at which we have just left it when M. Fere and my- self approached the study of this phenomenon. f We *Stricker, Le langage et la musique, Alcan, 1885; for the discussion with M. Paulhan, see Revtie pkilosophique, years 1883 and 1884, j^flj^m. ■\Thcorie des halhuinations {Revue scienii/igue, January, 1885). IMAGES. 31 introduced experiments in hypnotism, which enabled us to settle a number of undecided ques- tions ; from these experiments, which we shall briefly recapitulate, there follows a consequence which is important in connection with the seat of images. Hitherto we have refrained from defining this seat ; and we might yet with advantage main- tain, while adhering to what has preceded, that the image is simply localized "in the soul" and pos- sesses, as has been said, a purely spiritual existence. But this is not the case ; there exist precise, proved and incontestable facts which demonstrate that the image — or rather the corresponding nervous process — has a fixed seat in the brain, that this seat is the same for the image and the sensation, and that, finally, to sum the whole matter up in a single formula, the image is a phenoinenon which results from an excitation of the sensory centres of the cor- tex. We shall therefore expound what might be called a physiological theory of the image, or at least, if the phrase is too pretentious, a series of experi- ments which treat of the physiology of the image. These experiments were made in M. Charcot's clin- ical laboratory at the Salpetriere, on young hys- terico-epileptic girls, who were completely hypnot- ized according to the ordinary and frequently described processes.* We know that is possible to produce hallucina- tions of all the senses in hypnotized subjects during *For further details, I refer the reader to the work which I have written in collaboration with Dr. Fer6: Le magnetisme animal {Bibliotheque scientifiqiis internationale, Alcan, Paris). 33 THE PSrCHOLOGT OF REASONING. certain stages of the trance, and especially during somnambulism. These induced hallucinations form one of the most familiar psychical symptoms of hypnotism. The voice is generally used to pro- duce them. When the subject is suitably prepared, when the right moment has come, we have only to say to him, authoritatively, "There is a serpent," for him to see it crawling before him. This hallu- cination is subjective, personal to the subject, and consequently may be easily feigned ; but it presents so many objective characters that its existence can- not be doubted, at least in the cases in which these characters are present. Therefore we shall not stop to discuss the hypothesis of simulation again; in proportion as we proceed with our exposition, the reality of the phenomenon will be proved. How can the experimenter excite hallucinations by speech? How can he make the subject come to see a serpent or a bird merely by what he says to him? Can this phenomenon be explained? And is there any analogous phenomenon in the normal life of a wide-awake individual? Such are the questions which a psychologist should, in view of these expe- rimental hallucinations, put to himself. We raise these questions because, while investigating them, we shall show how experiments in hallucination may be useful to the theory of Images. When, during a conversation with a wide-awake person, we speak to him of the colour red, and he understands the meaning of that word, we raise zxy image in his mind, the image of red, by virtue of the association which has been established by educa- IMAGES. 33 tion between the word and the idea; but this created image is generally very feeble, very pale ; after being barely caught sight of, it vanishes, like a "super" who has merely crossed the stage. The word has excited in the wide-awake person a vision of red, but a short, rapid and defective vision. Dif- ferent circumstances may render the vision more durable and more powerful, even during the waking state. Here is a striking example of this. It is related that on the evening of the execution of Marshal Ney, several people were assembled in a Bonapartist room; suddenly the door opened and the servant, mistaking the name of one of the arrivals, who was called M. Mar^chal Ain6, an- nounced aloud: "Monsieur le Marechal Ney.-' At these words a thrill of fear ran through the gathering, and those who were present have since related that for an instant they distinctly saw in M. Marechal, Ney himself advancing in person into the middle of the room. Here we touch upon the suggested hallucination, if the phenomenon does not actually belong to that class. The hallucinations which are produced in the hypnotic state by the voice of the experimenter do not possess a different mechanism. The voice of the experimenter excites the auditory centre of his subject, and this centre, once awakened, transmits its excitation to the visual centre, by virtue of pre-established dynamical asso- ciations. Then the visual image arises and ob- trudes itself with so much the more energy that it reigns alone in the consciousness of the patient ; the part of his brain which is excited is the only part 34 THE PSrCHOLOGT OF REASONING. which reacts, and it consequently gives its maxi- mum. But let us put aside these particular condi- tions which make the image evoked so intense and transform it into a hallucination. What is import- ant for us to show is the fact that the phenomenon of suggested hallucination in hypnotism is not iso- lated from ordinary intellectual processes ; that, on the contrary, its germ exists in the images which people our mind during the waking state, and that hallucination may definitely be made use of as an exaggeration of the image in studying its properties. The first fact to v/hich we shall call attention, from the point of view of the physiology of the image, is the effect of achromatopsia or color blind- ness. It is known that a large number of hysterical subjects display an insensibility which extends over one entire half of the body and divides it vertically into two parts; this hemi-anaesthesia is usually accompanied by more or less pronounced sensory anaesthesias ; on the insensible side the hearing is enfeebled, the nostril smells odours with difficulty, and one-half of the tongue cannot distinguish the tastes of the foods which are placed upon it. But what really interests us most is the state of the eye. This organ shares with the others in the insensibil- ity. In most cases a concentric contraction of the visual field is observed, and at the same time the loss or enfeeblement of one or several sensations of colour, in other words, achromatopsia. This loss of colours occurs according to a definite order. The colour which is first lost is violet; green is second; this order is constant in all patients. In the case IMAGES. 35 of the other colours, two classes, which occur almost equally often, must be laid down; in the one, the patients lose violet, green, red, yellow and blue successively; in the other, the red and blue are inverted, and the series reappears thus: violet, green, blue, yellow and red. It is interesting to investigate the influence which achromatopsia might exercise upon coloured hallucinations which are suggested during hypnot- ism. M. Richer was the first to observe that if only the achromatoptic eye of a hypnotized subject is kept open, it is impossible to suggest any coloured hallucinations to her by the medium of that eye. If the patient have lost the colour violet, it is impos- sible to make violet enter into her hallucinations, and so on. Here are some examples of this: ''^ Bar, in the waking state, is achromatoptic in her right eye. Keeping her left eye closed, we make her see a flock of birds. To our questions on the colour of their plumage, she replies that they are all white or gray. If we insist, assuring her that she is mistaken, she maintains that she sees only white or gray birds. But the state of affairs alters if at that moment we open her left eye, whether her right eye be closed or not ; she is immediately enraptured with the variety and brilliance of their plumage, in which all the different colours are com- bined. "This experiment has been varied in many ways. Closing her left eye we show her Harlequin, and she describes him as all covered with gray, white or black squares. Polichinelle is likewise 36 THE PSrCHOLOGT OF REASONING. dressed in white or gray. "It is original, ' ' she says, "but it is not pretty." Immediately upon open- ing her left eye the notion of colour reappears, and Harlequin and Polichinelle appear to her in motley, as they are commonly represented."* The same rule appears to extend, as I have shown, to the spontaneous hallucinations of insan- ity. I have observed a hysterical lunatic, who was a patient of Dr. Magnan's at the Asile Sainte- Anne, continually possessed with the image of a man dressed in red. This woman was hemi-anaes- thetic and achromatoptic in the left eye; when her right eye was closed she continued to perceive her hallucination with her left eye, but the man who appeared to her was no longer red ; he was gray, and seemed as if surrounded by a mist. Thus blindness in one colour obstructs the hallu- cination — that is to say, the image of that same colour. How may this be explained? Very simply, if we consider achromatopsia as a cerebral phenom- enon, as a functional disturbance of the cells of the cortex affected by the sensation of colours. Since this functional disturbance places the same obstacle in the way of the hallucination as in that of the sensation of a given colour, it seems probable that the sensation and the image employ the same kind of nervous elements. In other words, the halluci- nation would take place in the centres where sense impressions are received ; it would result from an excitation of the sensory centres. What is said of the hallucination applies directly to the image. *P. Richer, Etudes cUniqites siir riiysteroepilepsie, p. 708, and. edit. IMAGES. 37 It will perhaps be objected that there are some hypnotized hysterical subjects in whom achroma- topsia does not prevent the suggestion of coloured hallucinations. But it seems to us to be easy to explain this departure from the rule. We shall confine ourselves to remarking that achromatopsia in hysterical subjects depends upon hemi-ansesthesia; that this loss has nothing definite about it ; that it is less a paralysis than a paresia, an inactivity of the nervous elements. These elements no longer respond to the call of their normal stimulus, col- oured light ; but there is nothing astonishing in their reacting when they are attacked from another side, by an excitation which comes from the auditory centres and is nothing else than verbal suggestion. Other facts may be given to corroborate the localization of the image in the sensory centre. A large number of observations collected by M. Fere show that a constant connection exists be- tween the special sensibility of the eye and the gen- eral sensibility of its integuments. When a cereb- ral lesion causes sensitive disturbances in the integuments of the eye, visual disturbances, such as achromatopsia and concentric or lateral shrinking of the visual field are, on looking a little closely into the matter, likewise met with. In hysterical hemi- anaesthesia, a connection is also observed between the sensibility of the conjunctiva and of the cornea and the special sensibility of the organ ; these two sensibilities are always affected to a similar degree. The interpretation of these and many other facts too numerous to be repeated here, has led M. Fere 38 THE PSrCHOLOGr OF REASONING. to the following conclusion : that there exist in undetermined regions of the encephalon sensitive centres which are common to the organs of the senses and to the integuments which surround them.* Now, if we carefully examine all that happens when a visual hallucination is produced in a hyp- notized subject, we see that in many cases the hal- lucination modifies the sensibility of the external membranes of the eye. In the cataleptic state, the conjunctiva and the cornea, outside the pupillary field, are generally insensible ; but as soon as the visual hallucination has been produced, in P for example, the sensibility of the external mem- branes returns to the condition in which it exists during the waking state; the membranes cannot be touched by a foreign body without exciting palpe- bral reflexes, t With the said M the hallucina- tion continues for several minutes on awakening, always producing a dysaesthesia of the membranes of the eye, which lasts exactly as long as the hallu- cination. With the said Wit , the unilateral hallucination produces a slight pain in the eye which is alone hallucinated; "I feel as if there were sand in that eye," says the patient. These three observations seem to show that the visual hallu- cination, or, in a more general way, the visual image, implicates the centre of vision. But we have not yet approached the most inter- *Ch. F^re, Troubles fonctionnels de la vision, pp. 149, 150 and 151. tCh. Fere, Les hysteriques hypnotiques coninte sujets (T experimenta- tion, etc. {Arch, de neurologie, 1883, t. VI, p. 122). IMAGES. 39 esting observations in this class of ideas. We have yet to speak of the chromatic phenomena produced by hallucinations of the sight. Let us first of all recall three physiological experiments v/hich may easily be performed with- out much apparatus. In the first experiment we take a card divided into two equal parts, the one red, the other white, and having at its centre a point for the purposo of fixing the sight ; if we gaze at this point for several moments, we see a green colour appearing on the white half. This is the chromatic contrast.* In the second experiment we gaze fixedly upon a little red cross with a black spot at its centre ; if we then turn our eyes to a sheet of white paper bearing a black spot, we immediately see a green cross appearing. This is the negative consecutive sensation. In the third experiment we take two cards, one red and the other green, and place them on a table, one a short distance before the other; then, with a sheet of glass held before the eye, we look at one of the cards through the transparency and at the same time try to obtain the reflected image of the other card in order to carry it on to the first ; as soon as the images of the two cards are superposed, their colours blend, and we obtain a resultant colour which is generally grayish (the exact tint depends upon the colour of the cards, *Without wishing to raise any complicated physiological problems here, we may recall the fact that a general agreement does not exist upon the ex- planation of simultaneous contrast and consecutive images. Helmholtz attributes the effects of the simultaneous contrast to an error of judgment; as for consecutive sensations, he localizes them in the retina, and explains them by Youno-'s theory and that of Fechner. For our part, we entirely share Dr. Parinaud's opinion, which assigns a cerebral seat to those two phenomena, and attributes to them as their sole cause a material modification of the nervous centres. {Soc. de BioL, May 13 and July 22, 1882), 40 THE PSTCHOLOGT OF REASONING. the intensity of the light, etc.). This is the blend- ing of complementary colours. We may repeat these three experiments with cards coloured by suggestion, that is to say with hallucinations of colour. If, as M. Parinaud has shown, we produce in a patient the hallucination of red on one-half of the white sheet, she sees green appearing on the other half. If, as we have ob- served along with Dr. Fere, we make a red cross appear on a white sheet, the patient, after having contemplated this imaginary cross for several mo- ments, sees upon another sheet of paper a green cross. Finally, if we teach her to superpose, according to the process described, cards coloured green and red by suggestion, the patient sees the resultant gray tint, which is produced by the blending of these two complementary colours. In view of these results, is it possible to doubt that visual hallucination results from an excitation of the sensory centre of vision? If it were other- wise, how could we understand that hallucination should give rise to the same chromatic effects as sensation? We may transfer all these phenomena revealed by the study of visual hallucination to the visual image itself. This extension of experience is so much the more legitimate since Wundt has shown that the simple image of a colour, contemplated for a long time in the imagination, gives rise to the consecutive sensation of a complementary colour. If we, in our minds, gaze fixedly for some moments at the image of red, we perceive, on opening our IMAGES. 41 eyes upon a white surface, a green tint.* It is difficult to repeat this experiment, for it demands a power of visuaHzation which everybody does not possess. To take myself as an example, I cannot imagine a colour clearly; I am a visucl of a very mediocre type. Therefore it is not astonishing that I fail to obtain a consecutive coloured sensation. But my excellent friend, Dr. Fere, easily succeeds in doing this. He can imagine a red cross so vividly as to see afterwards, on a sheet of paper, a green cross; thus he sees not only the colour, but the form.f These facts show the strict analogy existing be- tween the sensation, the hallucination and the image ; we may conclude from this that whether we have the sensation of red, whether we have the recollection of red, or whether we see red in a hal- lucination, it is always the same cell which vibrates, ij; So far we have been content to assert that the image has the same seat as the sensation, without seeking to determine anatomically what that seat is. The preceding experiments do not enable us to solve this last question, which is much more com- plicated and difficult than the first. We might here introduce the principal results of the study of cereb- ral localization, which seem to show that the sen- sory centres are situated at the level of the cerebral surface-layers, in a zone still ill-defined, probably *Cited by Bain in the Appendix to The Senses and the hitelleci. jTliis experiment affords an objective sign which allows us to recognize whether a person belongs to the visual type. tAll the preceding experiments have treated of the visual image. The reader will judge to what extent it is legitimate to extend the conclusion derived from them to the images of the other senses. 42 THE PSyCHOLOGT OF EEASONTNG. situated behind the motor zone. But we prefer to confine ourselves to the basis of hypnotic experi- mentation, from which we may still learn some- thing upon this subject. It is a primary fact in the study of hypnotic hallucinations that these sensory troubles, when they have a unilateral form, are transferable by the magnet.* This transfer is accompanied by a certain number of objective signs which exclude all idea of simulation ; thus the shifting of the phenomenon is followed, in certain subjects, by a shifting in the inverse direction, then by several other shiftings, phenomena which have been described in connection with the transfer of anaesthesia by the name of consecutive oscillations; further, according as the transfer is effected, the patient complains of pains in the head, which oscil- late from one side of the head to the other; these characteristic pains, which we have proposed to call transfer pains, are not diffuse ; they have a fixed seat, and that a most remarkable one. In the case of hallucinations of the sight, the pain in the head corresponds to the anterior part of the inferior parietal lobule, as M. Fere's researchesf in cranio- cerebral topography have enabled us to ascertain ; in the case of auditory hallucinations, the painful spot corresponds to the anterior part of the sphe- noidal lobe. These two localizations are in perfect asfreement with the results of clinico-anatomical reseaches; they therefore deserve to be taken into *Binet and Fere, Le transfert ^isyschique {Revue philosophique, January, 1885). tCh. Fere, Note sur quelqiies points de la to-pogra-pliie die cerveau {Arch, de phys. norm, et path., 1876, p. 247); Nouvelles Recherches sur la topographie cranio-cercbral {Revue d\T,iithrop.., 1881, p. 46S). IMAGES. 43 serious consideration. The centre of visual sensa- tions has been placed in the inferior parietal lobule, and the auditory centre in the sphenoidal lobe. It therefore seems permissible to consider that visual images and auditory images very probably result from the excitation of these two centres. We finally reach the same conclusion as Herbert Spencer and Bain, but with the advantage of pred- icating proofs at our disposal for what these authors considered as merely probable: "The renewed feeling, ' ' said Bain, ' ' occupies the very same parts and in the same manner as the original feel- ing." III. We have not yet finished our short study of Images. After having determined their seat in the brain, we shall proceed to indicate their principal physiological properties. Mr. Spencer calls images faint states, in oppo- sition to sensations, which are vivid states. The term is correct. The lack of vividness of images is one of the reasons which prevent them from being conveniently observed and which explains why their nature has so long been unrecognized. In order to study them it is necessary to compare them with consecutive images of sight, ^ phenomena which follow the impression of an exterior object on the retina. We know that consecutive images are of two kinds, positive and negative. Place a small red square upon a brightly lighted white surface ; look at this square for a second, then shut your eyes 44 THE PSrCHOLOGT OF REASONING. without strain, by covering them with your hand, and you see the red square appearing; this is the positive image. Repeat the same experiment by gazing for a long time at the red square, then, on closing the eyes or fixing them on a different point on the white surface, you will see this same square appearing, but instead of being red it will be green, the complementary tint ; this is the negative image. The consecutive image constitutes a transition type between the sensation and the ordinary image ; it is like the sensation inasmuch as it immediately follows the action of a ray of light upon the retina, and it is like the image inasmuch as it survives that action. The consecutive image is generally fairly intense ; it may be experimented upon with more result than the ordinary image. M. Parinaud has demonstrated the cerebral seat of the consecutive image by the following experi- ment {Soc. de Biol,, 13th May, 1882): "M. B^clard relates as follows, in his treatise on physiology, an experiment which is little known : 'The impression of a colour upon the retina awakens on the same point on the other retina the impres- sion of the complementary colour. Example : Shut one eye, gaze for a long time with the open eye at a red circle ; then shut this eye, open the one which was shut, and you will see a green aureole appear- ing.' (Edition dated 1866, p. 863.) "Thus presented, this experiment is open to criti- cism ; its very formula enunciates an error; but, re- stored to its true meaning, it contains the demonstra- tion of the proposition which I have just put forward. IMAGES. 45 "In order to give a proper account of the nature of the sensation developed in the eye which has not received the impression, let us first of all see what takes place in the eye which receives the impres- sion. "Shutting the left eye, for the moment excluded from the experiment, we gaze at a red circle on a sheet of white paper, or better, at a point marked at the centre of the circle, in order to fix the eye better. After some seconds the white background loses its intensity and the colour itself becomes dim. Drawing the circle away without taking our gaze off the point, we see appearing on the paper the image of the circle coloured green and brighter than the background ; this is the negative image. Shut the eye, and the image, after having disappeared for an instant, is reproduced with the same charac- teristics. "Let us now repeat Beclard's experiment — that is to say, at the moment when we draw away the circle, let us shut the impressed right eye and open the left eye, gazing always at the paper. "The image of the circle does not appear im- mediately. "The white of the background darkens at first, and it is only then that the image takes form, col- oured in green and brighter than the background. It is the same negative image, exteriorized by the left eye, as we recognized in the right eye which received the impression.* *M. Giraud-Teulon, who has repeated the experiment, attributes the same characters to it (Unpublished note sent to M. Charcot). 46 THE PSTCHOLOGT OF REASONING. "We may produce the same transfer with the positive image by varying the conditions of the experiment. "The exteriorization of the adventitious image by the eye which has not received the impression necessarily implies the intervention of the brain and, in all probability, the cerebral seat of the image itself."* This experiment on the consecutive image seems to me to be very important for our theory; I have repeated it a very large number of times. In the course of these studies I have noticed some curious phenomena. First of all, the experiment may be made with both eyes open. We gaze at a red cross with the right eye, keeping the left eye open, but preventing this eye from seeing the cross by inter- posing a screen. At the end of some seconds we shut the right eye; and shortly after the left eye, *M. Parinaud adduces a second proof, which seems to us much less satis- factory. He remarks that the consecutive image follows the intentional movements of the eye, but is not displaced when the optical axis is deviated by the finger. Now, a retinal image, he says, would be displaced in the mechanical deviation of the ball, as well as in its intentional movements. The conclusion does not seem to us to be just. It is readily admitted in psychology that we perceive the movements of bodies by the eye in tv>'o ways: ist, when the eye is steady and the image of the object changes its place on the retina; 2nd., when the eye is in movement and the image of the object does not change its place on the retina. This last case is that in which we follow a moving object with our eyes, for example a rocket rising in the air. It has moreover been remarked that the state of repose or movement of the eye translates itself into consciousness by the absence or the presence of the sensations which accompany the contractions of the ocular muscles; that is that our consciousness takes account solely of intentional movements. These two rules explain the majority of optical illusions relating to movement. Thus the consecutive images appear to move with the gaze, for in this case we experience muscular sensations which are the sign of the movement of the eye, and, in addition, the consecutive image is not displaced on the retina. When the eye is mechanically deviated, we have no muscular sensations, the eye seems steady; consequently, on the one hand the exterior objects, which are really steady, appear to move, for their image is displaced on our retina, considered as fixed, and on the other hand the consecutive images appear steady, for their image does not change its place at all on our retina, con- sidered as fixed. In short, eveiry object which appears to move with the movements of the eye ought to appear steady when the eye is mechanically deviated, and vice versa. These are the results of our psychical education. No argument, either for or against the retinal seat of the consecutive image can be drawn therefrom. IMAGES. 47 which has remained constantly open, sees the point on the paper at which it gazes become covered with a faint shadow, and at the middle of this darkened surface appears a green cross. We must also note the changes which take place when seeing the transferred consecutive image ; it appears, as M. Parinaud has very fitly remarked, after a certain delay; it never lasts very long, at least with my eyes ; it usually disappears at the end of two seconds, and the paper resumes its original white tint at the same time. But this is not all, and if we keep our eye fixed on the same point we see the paper, some seconds after, darken once more and the image reappear with the same charac- teristics of form and colour as it had at first. The number of these oscillations seems to depend on the intensity of the image; I have often counted three of them. I have also found that the other eye, the one which has gazed steadily at the red cross, preserves its consecutive image during all this time, and that we can, by opening and shutting our two eyes alternately, see the direct consecutive image and the transferred consecutive image succeed each other. This succession of the two images allows us to compare them. They do not always have the same characteristics; I have found that there is a fairly decided difference of tint for certain colours. For example, an orange-coloured wafer gives me a con- secutive image which is almost blue when seen directly, and almost green when it is transferred ; 48 THE PST'CIIOLOGT OF REASONING. this difference is maintained no matter which eye is used at the beginning of the experiment. The two images present practically the same tint for other colours. Another proof of the cerebral seat of the con- secutive image is that it sometimes appears long after the impression and in this case it resembles an ordinary recollection. Newton, by an effort of attention, was able to reproduce a consecutive image, produced by gazing steadily at the sun sev- eral weeks previously. It is well known, says M. Baillarger, that persons who are in the habit of using the microscope sometimes find objects which they have been examining for a long time reappear spontaneously some hours after they have left their work. M. Baillarger,* having worked some hours daily for several days at preparing specimens of brains with fine gauze, saw all at once gauze contin- ually covering the objects in front of him, and this hallucination was repeated for some days. This is an analogous case to that of M. Pouchet, who saw {Societe de Biologic, 29th April, 1882), while walking in Paris, the images of his microscopic preparations superposing themselves on exterior objects. This phenomenon is not rare; numerous examples are to be found for the seeking. This reviviscence of the long-expired consecutive image, a long time after the excitative sensation has ceased to act, completely excludes the idea that the con- secutive image is preserved in the retina ; the preser- vation is made in the brain, and, very probably, *Quoted by Taine, On Intelligence, p. 53. IMAGES. 49 when the image reappears, it does not involve the cones and rods of the retina in fresh activity. We may therefore admit, as a very probable fact, that the consecutive image has a cerebral seat. This conclusion is interesting for the psychologist ; because it leads him to establish a parallel between the consecutive image and the image of memory. In what do they differ? First of all, in intensity; the consecutive image is so vivid that it may be projected upon a screen and fixed there by draw- ing. Are there many recollections which could be exteriorized in the same fashion? Then, by the mode of appeai'ance; most frequently the consecu- tive image immediately follows a visual sensation, sometimes it appears spontaneously much later, and it is never excited by a psychical cause, by associa- tion of ideas, as are the ordinary images of memory. Observers have been struck with this fact. M. Pouchet has remarked that at the moment when the image of his microscopic preparations rose be- fore his eyes, he was in a cab, chatting with a per- son who knew nothing of science, and he has been unable to perceive the slightest connection between this image and the subject of his conversation. The comparison of the consecutive image with the image of memory is of considerable interest ; for experiment shows that the consecutive image pos- sesses a certain number of attributes, which further belong also to the image of memory. Thus: First, it changes its place with intentional movements of the eye and movements of the head when the look is fixed ; second, it becomes larger when the screen 50 THE PSTCHOLOGT OF REASONING. on which it is projected is drawn away, and shrinks when the screen is brought nearer; third, it is dis- torted with the inclination of the screen and it lengthens in the direction of the inclination. A real image, painted on the screen, behaves quite otherwise. If the screen be drawn away from the eye, this image becomes smaller; if the screen be brought nearer, the image becomes larger; if the screen be inclined, the image is distorted and shrinks in the direction of the inclination. This is what painters call foresJiortening.'^ In short, the consecutive image and the real image (the sensa- tion) present inverse properties up to a certain point. What is the reason of this? The question may be readily answered. Let us first of all suppose, for greater clearness, that the consecutive image has its seat in the retina, with the reservation of modifying our demonstration afterwards to make it agree with the theory of the cerebral seat. We must depart from the principle, so firmly established by Helmholtz, that every sub- jective sensation is perceived, exteriorized and localized in the same fashion as if it corresponded to an exterior object. Let the consecutive image be A' B', on the retina; if it be projected outside, on a screen held at E F, it will have the dimension of the line A B, because that would be the dimen- sion of an object which, placed at the distance of the screen, would make on the retina an image *It is only after a little exercise that one can succeed in giving an account of these changes in the dimensions of the image, because, as they do not correspond to any change in real dimensions, we have contracted the habit of correcting them. IMAGES. 51 equal to A' B' ; in fact, the two lines A' C and B' C are carried from the two extremities of the image to the optical centre of the eye and produced until they meet the line A B. Now let us alter the dis- tance of the screen, and what happens? As the subjective image is of constant size on the retina, it must assume on the screen the dimension of an object which, situated at the new distance where the screen is placed, would make on the retina an image equal to A' B'. Therefore we have only to calculate the successive sizes of an object subject to this condition of always producing at the back of the eye a retinal image of the same size, in spite of its changes of distance. In order to simplify the problem, we shall give the consecutive image the form of a circle; there- fore, we may replace the visual angle A C B by a right circular cone, with its vertex at C, and A C and B C as its generating lines. This granted, when the consecutive image is projected on a screen, E the screen cuts this cone, and the size and form of the conic section are those of the object which, at the distance at which the screen is held, produces a retinal image equal to A' B' ; consequently they 52 THE PSrCHOLOGY OF REASONING. are also those of the projected consecutive image. Thus, when the screen is held vertically (that is to say, perpendicular to the optical axis), the consecu- tive image must have a circular form, because the section is made in a plane perpendicular to the axis of the cone and is of circular form ; when the screen is inclined, the consecutive image must lengthen, because the section is oblique and of elliptical form; when the screen is drawn away, the image must become larger, because the section is made further from the vertex of the cone and becomes larger. This is confirmed by experiment. That this is not so for the real image, painted upon the screen, is because its apparent diameter augments when the object is brought nearer, dimin- ishes when it is drawn away, and diminishes in the direction of the inclination when it is inclined. We shall not dwell upon this point. One may perhaps be tempted to conclude from this demonstration that the consecutive image really has its seat in the retina, for it would not behave otherwise if it were retinal. But it is to be remarked that the transferred consecutive image possesses the same properties. We have several times stated that it enlarges and contracts when the screen is drawn away and brought nearer. Will it be maintained that this transferred image is retinal? Received by the right eye, it is exterior- ized by the left eye, which has remained closed until the last moment ; it is therefore very probable that it has not impressed the left retina. *'It is rational to admit," says M. Richer on IMAGES. 53 this subject, "that the retina has an exact represen- tation of itself in the cerebral visual centre. There exists a sort of cerebral retina each point of which is in intimate connection with corresponding points of the peripheral retina."* Therefore it is under- stood that an impression conveyed directly to a point of this cerebral retina (the consecutive image) produces the same effect on consciousness as an im- pression which would lie on the corresponding point of the peripheral retina, to right or to left, either above or below, or on the yellow spot. We willingly admit, until we have proof to the contrary, that the properties of the consecutive image are common to the ordinary image, to recol- lection for example, although they could not be observed in an image so feeble. But there are cases where the image, evoked by a person of healthy mind, attains a degree of intensity suffi- cient to exteriorize it. Brierre de Boismont, who endeavoured to impress upon his mind the figure of one of his friends, a clergyman, had acquired the faculty of evoking it whether his eyes were open or shut ; the image appeared to him to be exterior, situated in the direction of the line of sight ; it was coloured, its outlines were fixed and endowed with all the characteristics belonging to the real person. We earnestly invite those who possess the gift of visualizing to try the following experiment : Think of a red cross, project it on a screen and see if it behaves like a consecutive image, if it enlarges when the screen is brought nearer and contracts ^Etudes cliniques sur I 'kystero-epilefsie, 2nd editiofc, 1S85, p. 714. 54 THE PSrCHOLOGT OF REASONING. when it is drawn away. The success of this experi- ment would give a decisive confirmation to our thesis. Such are the positive characteristics of consecu- tive images, and probably of all images. They have also a certain number of equally important negative characteristics, which serve, as much and more than the first, to distinguish them from sensa- tions. We know that our sensations are directly modi- fied in consequence of the movements which we make; the aspect of my home is modified when I shut or when I open my eyes, when I come nearer it or go further away, when I press my eyes so as to see double, or when I interpose a prism so as to see it deviated, or when I reflect it in a mirror so as to have a symmetrical figure of it, or when I look at it through an opera-glass so as to have an en- larged view of it. . . . It is clear that none of these experiments has any influence on a mental image. When I think of an absent friend, and the visual image of his countenance is about to rise in answer to my thought, I might try in vain to modify the perspective of this image by changing my position, or to double it by pressing my eye. The attempt equally fails in the case of the con- secutive image. M. Parinaud has made an experi- ment in order to show conclusively that a consecu- tive image cannot be deviated by looking at it through a prism. We select the following passage from a manuscript note which he has been good enough to send us: IMAGES. 55 ''Gaze steadily," he says, ''with one eye at a thin strip of red paper on a white background ; after a minute, sHp between the strip and the eye a prism with 1 5 degrees of an angle at its larger base, keep- ing the gaze fixed, without trying to follow the dis- placement of the strip. You then see the green consecutive image detach itself from the upper part of the red strip. In order to make sure that it is only the image of the paper that is displaced, and that the consecutive image has not undergone devi- ation in the inverse direction, recommence the experiment by covering only a part of the red strip with the prism ; the consecutive image, if the eye does not change its place, protracts exactly that part of the strip which has not undergone the prismatic refraction." To sum up, sensations and images form two groups of phenomena which are distinguished by definite characteristics, positive and negative equally. CHAPTER III. REASONING IN PERCEPTION. In external perception the images which arise in us from contact with objects derive a group of proper- ties from their origin which are entirely wanting in isolated images, which we studied in the preced- ing chapter. Directly suggested by exterior im- pressions, they associate themselves organically with these impressions, so as to form an indivisible whole which corresponds to the idea of a single object. By means of this sensory bond each image consequently undergoes all the modifications which the sensation directly experiences. Practically, as regards the observer, it behaves like a true sensa- tion. The chapter which follows might therefore be entitled : ' ' TJic properties of images zvJdcJi are asso- ciated zvitJi sensations. In the study of these phenomena we shall turn once more to hypnotic hallucinations, for in the normal state they are too weak to be observed. But here a preliminary objection arises: How can the hallucination be of use in the study of normal perception, an operation which is produced by a cooperation of the senses and the mind? Is the hallucination not a sort of delirious conception 56 REASONING IN PERCEPTION. 57 which arises wholly from a diseased brain ? When we say to a hypnotized subject: There is a serpent! and when, looking at the ground, she sees the serpent crawling towards her, what is real, what is objective in this apparition? Such is the objection which may be made a priori. But by carefully observing the hypnotic hallucination (the only one we shall refer to), and also by replacing mere observation by experiment, we find that a part of sensation enters, if not always, at least often, into this phenomenon. This is perhaps not an absolute rule, but the case is very common. Here is a first experiment which proves this: We present a pure white sheet of paper to the sub- ject and say to him: ''See, here is your portrait." The subject immediately sees his portrait appearing on the white surface, he describes the pose and the costume, adding to the suggested hallucination with his own imagination, and if the subject be a woman, she is usually dissatisfied, finding the por- trait little flattered. One of them, who was pretty enough, but whose complexion was covered with little freckles, said to me one day when looking at her imaginary portrait : "I have a great many freckles, but I have not so many of them as that." When the subject has contemplated the white card for some time, we take this card and shuffle it amongst a dozen cards of the same kind ; there are now thirteen similar cards, and we would be unable to recognize the one which carried the hallucination if we did not take care to mark it after having taken it from the hands of the patient. But the 58 THE PSrCHOLOGT OF REASONING. patient has no need of marks; if we offer her the bundle of cards, telling her to look for her portrait, she recognizes the first card, usually without mak- ing a mistake ; better still, she always holds it out in the same way, and if we reverse the card accord- ing to its edges, she sees the imaginary portrait upside down. But there is something still more cogent. If we photograph the white card and show the photographic proof to the patient ten days, twenty days or a month after, she will still recog- nize her portrait on it.* The most simple way of explaining this local- ization of the imaginary portrait is to suppose that the hallucinatory image is associated — in an uncon- scious manner — with the visual impression of the white card ; so that every time this visual impres- sion is renewed it suggests the image by association. There are always some special details on a paper card, however white it may be ; we are able to find them with a little attention ; the patient perceives them instantaneously by means of her hyperaes- thetic visual sense; these details serve her as the point of identification on which to project the image. They are, as it were, the nails which fix the imaginary portrait on the white surface. This is so true that the portrait experiment is more surely successful when ordinary paper rather than Bristol board is used. In a general way the more visible the point of identification, the more durable is the hallucination. *Clearly the experiment does not succeed every time, but one success is sufficient, under conditions which exclude fraud, to give us the right to take it into account. REASONING IN PERCEPTION. 59 We owe to M. Londe, the chemist of the Sal- petriere, the following corroborative fact : Wit — , being in a state of somnambulism, he shows her the engraving of a photograph representing a view of the Pyrenees, with some asses climbing a hill ; at the same time he says to her, "See, this is your portrait; you are quite nude." When she awoke, the patient chanced to perceive the engraving, and furious at seeing herself represented in a state too near that of nature, she jumped up and destroyed it. But two photographic proofs, which were care- fully preserved, had already been taken from this engraving. Every time the patient sees them she stamps with anger, for there she always sees herself represented as nude. At the end of a year the hal- lucination still remains. This exceptionally long survival of the hallu- cination is clearly explained by the point of identi- fication theory. In reality the photograph presents to the patient an immense number of points of identification, which, being associated with the hallucinatory image, evoke it by accumulating their effects with an irresistible force.* The most curious thing about this observation is that the patient does not see these points of identification, or rather does not take account of their nature, for it is very essential that she should see them so as to project her hallucination ; but she does not succeed in recognizing that they form, by their union, a view of the Pyrenees. It is useless to endeavour to lead *It has been long remarked that one recollection is much more surely recalled than another, when it has a larger number of lines of association at its disposal. 6o THE PSrCHOLOGl' OF EBASOlYING. her from her error; her portrait is all she sees on the photograph. These few examples will be sufficient to show that hypnotic hallucination may, like perception, contain two elements: an impression of the senses and an exteriorized cerebral image. Perception, said Taine, is a true hallucination.* It is true that the mode of formation is not the same in both cases. The hypnotic hallucination is formed by an image suggested by speech, which is associated with a point of identification, while in perception the image is directly suggested by an impression of the senses. But between these two acts lies a third, which forms a transition between them, the illusion of the senses. The hypnotic illusion of the senses differs in one point only from the hypnotic hallucination, in that it consists of the transformation of an exterior object, while the hal- lucination creates an entirely imaginary object. Say to a subject, while showing him a hat : There is a cat, or a bird, or a house; and you produce a hypnotic illusion. Pronounce the same words without showing any object, and you suggest a hal- lucination. But the existence of that object which serves as substratum for the hypnotic illusion does not appear to have any importance, since it may be transformed in a hundred ways. The ordinary error of the senses, a trouble so frequent that everybody knows it by experience, takes its place alongside the hypnotic error of the senses. Who has not heard a burglar's step in the creaking of a piece of furni- tA. Binet, L ^Hallucination {Revue philosophique, April and May, 18S4). REASONING IN PERCEPTION. 6 1 ture; who has not seen a human figure in the con- fused forms of a landscape by night? These illu- sions are distinguished from those of hypnotism by their mode of formation. In the hypnotic state the image which transforms the object is suggested by speech, it comes from within ; in the normal state the false image is suggested by a defective vision of the object, it comes from without. But apart from this difference, the two are alike. In short, the illusion of the senses is intimately connected with exterior perception, which it in a manner counter- feits. Consequently perception and hallucination are bound together by an uninterrupted series of intermediate states. Thus we are permitted to consider the ordinary illusion of the senses, the hypnotic hallucination, and finally the hallucination, as more and more accentuated distortions of per- ception. This proved, we proceed to utilize these facts of the morbid state in the study of the normal state. Brewster was the first to observe that if the eye of a person in the state of hallucination be pressed, the imaginary object is seen double. The fact has been confirmed by observations made by Paterson, Despine and Ball. This last named doctor has reported the most curious example. It concerned a hysterical young girl who, in the crises of natural somnambulism, saw the Holy Virgin appearing to her in a resplendent costume. This miraculous apparition was invariably doubled by ocular pres- sure; two Virgins appeared before her. M. Fer6 has in his turn found that by operating on hys- 62 THE PSrCHOLOGT OF REASONING. terical subjects who can be hypnotized it is possible to repeat this curious experiment as often as desired. How shall this Jialhicinatory diplopia be ex- plained? It is clear that we are unable to double a mental image directly by pressing on the eye. If I think of an absent friend, I shall never succeed in seeing him double by pressing on my eye. If, therefore, the visual hallucination may be divided under these circumstances, that indicates that it is not ''altogether image"; in reality it is associated with an impression of the senses — that is to say, with an exterior point of departure; the ocular pressure doubles this point, and the cerebral image shares this doubling consecutively by a sort of re- bound. Now, this is precisely what occurs in visual per- ception. When we look at an object while touch- ing or pressing on our eye to make it deviate from its normal position, we see the object double; the object, we say. Now, what is an object? A group of sensations and images; the images are therefore doubled, like the sensations; the sensory diplopia is therefore accompanied by a mental diplopia. But the fact is not readily apparent. It would not be noticed, save for the hallucination, which hyper- trophies it, rendering the image enormous and reducing the sensation to almost nothing. In this way pathological facts instruct us regarding the normal state. We learn here that in our percep- tions the image is so firmly bound to the sensation that it indirectly undergoes its modification ; it is doubled when the sensation is doubled. REASONING IN PERCEPTION. 63 M. Fere has replaced ocular pressure by a prism. Placing a prism before the eye of a patient in the state of hallucination, he found that the hallucina- tion was doubled as before, and that, further, one of the images underwent a deviation whose direc- tion and value were according to the laws of optics. It will be fully understood that the experiment was made when all exterior objects whose modifications might serve as marks were removed from the visual field of the patient. For example, the patient is inculcated with the idea that a profile portrait is on a neighbouring table. If, without forewarning, a prism be interposed before one of her eyes, the patient is astonished to see two portraits, and the one which is deviated is always placed according to the laws of optics. (Ch. Fere, Soc. Biol., 29th Oct., 1 88 1.) This second experiment, like the first, instructs us regarding the history of our nor- mal perceptions ; for normally, when we place a prism before one of our eyes, the objects which we see through the prism appear to us deviated. Now, this deviation of the objects implies a deviation of the images; the prism, under certain conditions, deviates an image. Thus we find, in the centre of the normal life, the germ of this curious experiment in hypnotism. We have ourselves contributed to the develop- ment of these studies by replacing the prism by a large number of other optical instruments. The principle being settled, the experiments offer scarcely any interest save that of curiosity. We shall confine ourselves to mentioning a few, refer- y^ 64 THE PSrCHOLOGT OF REASONING. ring for details to our articles on hallucinations. If, while the patient is contemplating the suggested imaginary object, for example a tree on which a bird is sitting, we place an opera-glass before her eyes, she immediately declares that the tree is be- coming very large and is drawing nearer. If, revers- ing the opera-glass, we make the patient look through the objective glass (the large end), the tree suddenly recedes, shrinks, and the bird becomes completely invisible. The interest of this experi- ment lies in the remarks with which the patient, in the state of somnambulism, accompanies these changes in the imaginary object. The said Wit — experiences a most lively astonishment every time. When I make her look at a bird perched on the branch of a tree, she does not in the least under- stand how this bird can be quite near to her one moment and far distant the next. I tell her sev- eral times that the bird changes its position, that it flies nearer and then goes away. But she rejects this explanation entirely, with the objection that the tree also appears to occupy different positions. I reply that it is impossible, that the tree has its roots buried in the ground and cannot leave the place where it is planted. Then she concludes that her eyes are out of 'order, and that it is they which change the apparent distance of the objects. This conclusion is really a very reasonable one, it being stated that the patient does not know that the eye- piece and the objective of an opera-glass are placed alternately before her eyes. It is important to notice that the hallucination REASONING IN PERCEPTION. 65 is modified only when the opera-glass has been adjusted to the sight of the patient. Why? Be- cause it is only then that the opera-glass modifies her visual sensation ; it enlarges the surface of the extej-ior body to which the image is applied, thus enlarging the image, which acts like a drawing on an india-rubber film. This experiment, like the preceding ones, ex- plains the normal state. Without dwelling on the matter, let us merely remember that in approaching a person our visual sensations are gradually modi- fied ; at the same time the images produced by these sensations are modified in the same way. If we are at first very far away, we see a black spot of unrecognizable character; then this spot becomes an object longer than it is broad, then we distin- guish a person, then we know it to be a man, then a man of such and such a kind, and finally we recognize a certain man. The images change in proportion as the sensations are modified by our approach; they become more abundant, more defi- nite, and they finally permit an act of individual recognition. Hallucination renders this phenome- non of the induction of sensations into images very apparent. In other experiments we have replaced the opera-glass with a lens, which enlarges an imaginary portrait and at a certain distance reverses it, by a bifracting crystal v/hich produces a special and somewhat complicated doubling, and finally by a microscope, which produces a much greater enlarge- ment than the lens. But in these different cases it 66 THE PSrCHOLOGT OF REASONING. is always a matter of the same phenomenon of refraction, and when we know one of them we are able to understand them all. We shall describe, in conclusion, the mirror ex- periment. If we produce a hallucination on a fixed point, such as the hallucination of a cat on a neigh- bouring table, it is possible to get this imaginary- object reflected in a plane mirror, provided that this mirror reflects the point on the table where the imaginary animal is seated. The patient conse- quently sees two cats; both of them are imaginary, but it may be said that the reflected one is still more imaginary than the other. In fact, if the patient is directed to seize these animals, she readily catches the one on the table, but when she wishes to seize the reflected one her hand encounters the front of the mirror, which prevents it from going further. Moreover, observing things more closely, it is noticed that the mirror gives a syninietrical image of the imaginary object, as if it were a real object. It is in this way that an imaginary in- scription on a sheet of paper is seen reversed in the mirror. All these results are explained by the existence of the reflected point of identifi- cation. Here we have a case which clearly establishes the transition between hallucination and perception. It is an example of an illusion of the senses, which happened to be reflected by a mirror. One of my friends has related to me that, starting one night out of his sleep, he saw a human form before his window, which was faintly lighted ; shortly after, he REASONING IN PERCEPTION. 67 recognized that this apparition represented the Vir- gin; she was standing, stretching out her open hands, and from each finger proceeded a ray of fire. At the side of the window there was a cupboard with looking-glasses ; the Virgin was reflected in the looking-glass like a real object ; the second image was absolutely similar to the first; the attitude was the same, the open hands were surrounded by the same luminous aureole. My friend, who is not in the least superstitious, did not allow himself to be deceived by this apparent miracle. On approaching the window he found that the illusion arose from a white cloth hung on the fastening. As was to be expected, the image of the cloth was reflected by the looking-glass. Although this phenomenon may appear too natural to deserve mention, we mention it because it shows that one and the same rule extends to hallucination, illusion of the senses and to percep- tion. These comparisons are exceptionally instruct- ive in the study of perception. We now understand that when we see a real object reflected in a mirror there happens some- thing which is analogous to the reflection of a hal- lucination and of an illusion. The mirror, consid- ered from the point of view of perception, is a sort of repeater; it repeats the visual sensations which the object produces on us directly. These repeated sensations give rise, as if they were direct sensa- tions, to an interpretation, to the construction of an exterior object by the mind — that is to say, definitively, to a suggestion of images. We may 6S THE PSrCHOLOGT OF REASONING. therefore say that in the normal state a mental image is reflected in a mirror when it is connected with a sensation. We refer the reader who may desire further details regarding these phenomena of optical hallu- cination to the monograph on hallucination pre- pared by us in collaboration with M. Fer6. The aim which we pursue here is not to study hallucina- tion, but to explain exterior perception by hallu- cination, which is a very different thing. II. Hypnotic experiments on visual hallucinations have enabled us to penetrate in part into the mech- anism of our normal perceptions. The principal conclusion which is drawn from them is as follows: When an exterior object conveys an impression to our senses, the mind adds, upon its own initiative, a certain number of images to the sensations expe- rienced. These images, which complete the knowl- edge of the exterior and present object, do not remain inert and immobile in the presence of the sensations, like two bodies which have no chemical affinity for each other, or like two algebraic quanti- ties which are simply connected by the sign -{-. It is more than a juxtaposition. In reality a combi- nation of sensations and images is formed, and although these two elements come from very differ- ent sources, since one is sensory and the other ideal, they unite so as to form a single whole. This is proved by the fact that every time the REASONING IN PERCEPTION. 69 group of sensations is modified, a corresponding modification in the group of images follows. If the sensation be deviated by a prism, the image is deviated ; if the sensation be enlarged by an opera- glass, the image is enlarged; if the sensation be du- plicated by a mirror and made symmetrical, the image is reflected and becomes symmetrical. This resonance on the part of the image is a phenomenon which occurs every day, every hour and every instant in our sensory perceptions — that is to say, quite close at hand. If we do not notice it, it is because it is too delicate, too slight. To render it more appar- ent we must have recourse to the hallucination, which magnifies it. In common with many authors, we shall apply the name percept to the product of perception — that is to say, the images of the exterior object which are definitely due to and bound to the excita- tive sensation. We have yet to study the bond which unites the sensation to the image. The preceding experi- ments have proved its existence without making its nature known. We may consider external perception as a syn- tJietic operation, since it results in the uniting of the information actually furnished by the senses to the information furnished by preceding experiences. Perception is a combination of the present with the past. To perceive a body which is actually in the field of vision, to recognize in it a certain form, size, position in space, certain qualities, etc., is to unite in a single act of consciousness actual elements 70 THE PSrCHOLOGT OF REASONING. — that is to say, the optical sensations of the eye — • and past elements — that is to say, a crowd of images; it is to make a single body out of these unconnected elements. This is a phenomenon which completely escapes consciousness; by con- sulting that witness alone, the operation of perceiv- ing an object appears to be an easy and natural act which demands no effort of reflection on our part; that is in reality an illusion. Experiment and reasoning prove to us that in all perception there is work. But the amount of work is not constant ; it is clear that it varies according to circumstances. It would be wrong to think that there is only a single kind of perception. Perception is a form of activity which has a very variable nature, for by one of its extreme limits it encloses conscious reasoning, com- posed of three verbal propositions, and at the other end it becomes identified with the most elementary and automatic acts, such as reflexes. The amount of work expended in perception increases in an ascending series and even becomes very consider- able when we approach reasonings in which a sen- sible amount of reflexion and comparison occurs ; inversely, the work decreases when we descend towards reflex actions, without, however, vanish- ing altogether. It is therefore important to give some examples of the different kinds of perception. Let us begin with the lowest forms. "First of all,"* says Mr. Sully, in describing the degrees of visual perception, ''comes the con- *James Sully, Illusions, p. 23. BEASON/NG IN PERCEPTION. 7 1 struction of a material object of a particular figure and size, and at a particular distance — that is to say, the recognition of a tangible thing having certain simple space-properties, and holding a certain relation to other objects, and more especially our own body, in space. This is the bare percep- tion of an object, which always takes place even in the case of perfectly new objects, provided they are seen with any degree of distinctness. . . . This part of the process of filling in, which is the most instantaneous, automatic and unconscious, may be supposed to answer to the most constant and there- fore the most deeply organized connections of ex- perience. "The second step in this process of presenta- tive construction is the recognition of an object as one of a class of things^ — for example, oranges, hav- ing certain special qualities, as a particular taste. In this step the connections of experience are less deeply organized, and so we are able to some ex- tent, by reflection, to recognize it as a kind of intel- lectual working up of the materials supplied us by the past. "A still less automatic step in the process of visual recognition is that of identifying individual objects, as Westminster Abbey, or a friend, John Smith. The amount of experience that is here re- produced may be very large, as in the case of recog- nizing a person with whom we have had a long and intimate acquaintance. . . . It is further to be observed that in these last stages of perception we approach the boundary line between perception 73 THE PSrCHOLOGT OF REASONING. and inference. To recognize an object as one of a class is often a matter of conscious reflection and judgment, even when the class is constituted by- obvious material qualities which the senses may be supposed to apprehend immediately. Still more clearly does perception pass into inference when the class is constituted by less obvious qualities, which require a careful and prolonged process of recollection, discrimination and comparison for their recognition. . . . To say where the line should be drawn here between perception and observation on the one hand, and inference on the other, is clearly impossible." We may add that perception, in the highest steps of its development, assumes a particular char- acter. In rudimentary perception the mind simply infers from the sensations which it receives by one of its organs (for example, the eye) that the object has yet other properties which the other senses would perceive if it were necessary and if we wished it; thus when we look at a red-hot bar of iron, the red colour revives in us the idea of heat, which we might directly experience by bringing our hand near to the bar. Such a perception amounts to a substitution of sight for touch. But it is quite otherwise with the more complex perceptions which belong to reasoning properly so called. When we recognize that a plant belongs to the soap-worts or the lilacs by the inspection of a single leaf, when we discover the horn of a young stag, the claw of a wild boar or a wolf, on the mould of a forest track, the sensation received by REASONING IN PERCEPTION. 73 our eye evokes the image of objects which we can- not at the moment see. These operations are, however, always of the same kind, images suggested by an actual sensation, and there is no reason to believe that the mechanism of this suggestion is different in the two cases. To sum up, we may reduce all perceptive acts to two types: specific recognition and individual recognition. It would be interesting to know if individual perception begins by being generic, and only gradually attains, by a regular progression, to its complete development. According to this hypothesis, when we see a person whom we know, we perceive him at first as a solid body, then as a man, and finally as such and such a person. This pro- gressive development exists; it is not only prob- able, it is real. This is proved by the following experiments in hypnotism. Among the effects which suggestion is capable of producing in a hypnotized person systematized ancEsthesia is certainly one of the most interesting. This operation consists in rendering a person or an object invisible to the subject; it is, properly speak- ing, the isolated suppression of a particular percep- tion.* We still remember the effects which the first experiment in anesthesia had on one of our sub- jects, the said W . We made this experiment along Avith M. Fere. W being in the trance, we suggested to her that she would not see M. Fere *Binet and Fere, Le transfert {Revtie fihiLosoihique, January, 1SS5). An analysis of these experiments has been published by M. Richer {oj>. cii., p. 724 et seq.). 74 THE PSrCIIOLOGT OF REASONING. when she awoke, but that she would be able to hear his voice. Upon her awakening, M. Fere places him- self before her; she does not look at him; he holds his hand out to her, but she makes no gesture. She remains quietly seated in the arm-chair where she had just awakened; we are seated on a chair by her side. After some time she expresses astonish- ment at not seeing M. Fere, who was then in the laboratory, and asks us what has become of him. We reply: "He has gone out; you may return to your ward." M. Fere then stands before the door. The patient rises, bids us good-day and proceeds towards the door. Just as she is going to put her hand on the knob she strikes against the invisible body of M. Fere. This unexpected shock makes her tremble; she makes a fresh attempt to go on, but meeting the same inexplicable resistance, she begins to be frightened and refuses to renew the attempt. We seize a hat which is lying on the table and show it to the patient. She sees it perfectly Vv^ell, and assures herself, with her eyes as well as v/ith her hands, that it is a real body. Then we place it on M. Fere's head. The hat appears to the patient as if it were suspended in the air. Words could not express her astonishment ; but her sur- prise reaches its climax when M. Fer6 lifts the hat from his head and salutes her several times; she sees the hat, which is sustained by nothing, de- scribe a curve in the air. At this sight she declares that "this is no miracle," and supposes that this hat is suspended by a thread. Thereupon she gets REASONING IN PERCEPTION. 75 on a chair to try and touch this thread, but she does not succeed in finding it. Tlien we take a cloak and hand it to M, Fere, who puts it on. The patient, who continues to gaze at this cloak with a look of amazement, sees it move in the air and take the form of an individual. "It is," she says, "like an empty manikin." As we speak the furni- ture moves and rolls noisily from one end of the room to the other (it is only the invisible M. Fere who is displacing it); the tables and the chairs are overturned, then order succeeds to chaos. The things are put back in their places, the de-articulated bones of a skull, scattered on the floor, are brought together and fitted again ; a purse opens of itself, and the gold and silver pieces tumble out of it and in again. This experiment on the invisibility of M. Fere had been made on the 20th of May, 1884. At the end of the proceedings we omitted to render M. Fere visible, which could have been done by hypnotizing the patient again and assuring her authoritatively several times that she could see M. Fere. On the 23d of May M. Fere was still invis- ible. We wished to bring this phenomenon of anaesthesia to an end by a new suggestion ; then we observed a very remarkable thing. It was first of all found, to the surprise of every- body, that the patient not only ceased to see M. Fere, but had lost all recollection of him, although she had known him about ten years. She remem- bered neither his name nor his existence. After having put her in the trance we had considerable 76 THE PSrCHOLOGT OF REASONING. trouble in making M. Fere visible to her eyes; once awakened, she at last saw his person again, but, curiously enough, she did not recognize him, and took him for a stranger. It was most comical to see her get angry when M. Fere thee-and-thou'd her when speaking to her. Some days after, the patient had in the ward one of the bad attacks of hystero-epilepsy to which she is unfortunately subject. This attack completely swept away the last traces of the ansesthesia, and consequently the patient recognized M. Fere at last, without suspect- ing that during four or five days she had taken him for a stranger who was visiting the staff. We find in this last experiment,* which in a manner happened by itself — these are the best — an interesting application of the law of retrogression, the importance of which, in the destructions and reconstructions of the memory, has been shown by M. Ribot. It is really a general pathological law. Systematized anaesthesia consists, from the psycho- logical point of view, in the paralysis of an individ- ual perception. Here we see the anaesthesia disap- pear little by little, by degrees, sufficiently slowly to allow us to perceive its progress. The patient, who had at first lost the perception of M. Fere completely, begins, under the influence of a curative suggestion, by perceiving his person without recog- nizing it. The generic perception has reappeared ; the individual perception, which is more complex, is still paralyzed ; she sees a man without knowing *We mention only one experiment, but it is not unique. It appears to be the rule that systematic anajsthesia disappears in the manner indicated. HEASONING IN PERCEPTION. 77 who he is. Then the attack comes, one of those great internal catastrophies which clear away the accumulation of a toxic substance. Then the individ- ual perception reappears, and recognition takes place. This revival of the perception, which is recon- structed bit by bit, following the order from simple to complex, from the general to the individual, demonstrates the hypothesis which we have ad- vanced ; the different orders of perception which are distinguished by the names of generic, specific and individual perception, are only the more or less advanced steps of one and the same process. A perfect continuity exists between the simplest per- ceptions, as for example, the perception of a colour, and the complicated perceptions which verge upon logical and conscious reasoning; and in short a sin- gle act, in developing, in evolving, begins by being a simple perception and is transformed by degrees into a complex reasoning. A comparison will bring this idea into a graphic form. The point of departure of every perception is an impression of the senses; this initial element is like a nucleus around which layers of images are concentrically arranged. But these layers are not identical ; the images which the sensation suggests first, and which form the innermost and firmest layer, represent the physical properties of the ob- ject, form, size, physical consistence, weight, etc., and its simplest specific properties. The proof of this lies in the fact that these properties are the first to be perceived when systematized anaesthesia begins to disappear. On the contrary, the images 78 THE PSrCHOLOGT OF REASONING. representing the individual characteristics of the object constitute the most superficial and conse- quently the most unstable layer. Formed last of all, they are the first to disappear under the influ- ence of an inhibitory suggestion. We have hitherto considered only a single aspect of the percept, describing it as a synthesis of sensa- tions and images. From the logical point of view, the percept is a judgment, an act which determines a relation between two facts, or in other words, an act which affirms something of something. We content ourselves with reproducing an example cited by M. Paulhan in a little book which is worth more than many more voluminous works. "I have a book before my eyes, and I affirm that it is yellow. If we analyze this judgment, we find that what I affirm is the co-existence of a real sensation (the colour yellow) with other sensations which I have or can have (the white colour of the edges of the book, the black colour of the printed letters, sensations of resistance, of weight, etc.). But what is the nature of the act by which I believe these different sensations are united together? There is nothing in the mind save the cohesion of these different sensations. . . . Judgment therefore becomes reduced to an association of images, for the time being indissoluble; it is often accompanied by an affirmation expressed by words thought, pronounced or written (a verbal proposition), but it may exist independently of all expression ; it may consist solely of images."* *F, Paulhan, La physiologic de Vesprit^ p. 73. REASONING IN PERCEPTION. 79 This is the first time we have had to speak of the logical value of an association of images. This question has been treated at length by contempo- rary English psychologists; we can only refer to their works, where one will find it established that the aim of all judgment is to affirm a relation of resemblance, co-existence or of sequence between two things;* that this affirmation, this belief, this judgment, are the external effects of an internal fact, the association of images present to our minds ;f and that, finally, as a general conclusion, every time that two images are closely associated, as for example, the image of a stone thrown in the air and the image of its fall, or even indissolubly associated like the image of a thing possessing resistance and the image of a thing possessing ex- tension, we believe that the things thus bound together in our mind are bound together in the same fashion in reality.:]: This amounts to saying that we exteriorize an association of images as we exte- riorize an image. III. We have just seen that the percept is a compli- cated structure, made up of sensations and images, and evidently formed of several layers. We are already a long way from the common opinion, according to which the function of the mind which perceives an object is that of the sensitive plate of a *J. S. Mill, Logic, pp. 71 and 73. fH. Spencer, Princi:ples of Psychology, Vol. 11, p. 426. %]. S. Mill, Examination of Sir ]A^illiani Hamilton' s Philosophy. So THE PSrCHOLOGT OF REASONING. photographic apparatus; in proportion as we get still nearer to the heart of our subject, we shall be more and more convinced of the insufificiency of that com- parison. We have several times, in alluding to the psy- chological nature of perception, seen in it the result of unconscious reasoning. Although this point is generally admitted by contemporary psychologists, save for some variations and some minor reserva- tions, it forms too important a part of our subject to allow us to accept it without discussion and without proof. This is a question which deserves to be attacked directly. Before discussing a problem, its terms must be very accurately stated. We do not intend to com- pare perception with formal reasoning in all par- ticulars. It is plain, if the proposition be under- stood in that sense, that what we are maintaining becomes a paradox. It is paradoxical to maintain that the act of recognizing an object by sight or touch resembles a syllogism. Therefore we do not go so far as that ; and the reason why we dwell upon this matter is in order to beg our critics not to attack us by trying to refute what we have never said. What we do say, what we believe to be true, and what we shall proceed to demonstrate, is that in formal reasoning there are essential charac- teristics which we again find in external perception ; that these two acts, so dissimilar in appearance, have yet the same internal structure, the same ossature. To employ a comparison drawn from natural history, external perception is an act of REASONING IN PERCEPTION. 8 1 reasoning in the same way as the amphioxus, which has no vertebrae, is a vertebrate. To demonstrate this proposition, we may take at hazard an example of external perception and an example of formal reasoning, and compare the two. Let us compare the perception of an orange with the familiar syllogism of the schools: All men are mortal; Socrates is a man, Socrates is mortal. When we look at an orange we experience a cer- tain number of impressions. There is at first a visual impression of colour, of lights and shades, formed really by a very complex aggregate of sim- ple sensations. The muscular apparatus of the eye, awakened by the excitation of the retina, becomes the seat of contractions which are accom- panied by definite muscular sensations; the contrac- tion of the pupillary opening, the convergence of the axes of the two eyes, the contraction of the muscle of focal adaptation, the movements of the eyes in their sockets, etc., must be noted; there are also the movements of the head, neck and trunk, which are unconsciously performed so as to allow the luminous rays to reach the surface of the retina and the most sensitive part of that surface — that is to say, the yellow spot. These are almost all the real sensations which we receive from the object or in connection with the object; everything else about it is indirectly known, in the state of images. Thus the direction and the distance of the object — that is to say, its position in space — and its size, are three important facts furnished, not by the senses, but by the mind. This is not all. We 82 THE PSrCHOLOGT OF REASONING. believe we see — that is to say, we see by the mind's eye — the spherical form of the orange, its glossy and dotted surface, the juice which it contains, the complicated arrangement of its internal parts, the presence of seeds, and at the same time zve believe we feel its weight, its slightly elastic consistence, its odour, its taste, and we believe zue hear its name pronounced. If we continue to look at the orange, we induce the revival of images relating to its practical utility, to the act of cutting it with a knife, of carrying it to the mouth, of sucking it and throwing away the pulp and the pips. In short, there is an immense number of images which cannot even be mentioned because they are personal to each observer, and dependent upon his past experience and his scientific education. All these images are revived, to whatever degree, by the presence of the object, and gravitate around that sim- ple impression of a yellow spot, received by the eye. In a subject whose actions have been rendered entirely automatic, this suggestion of images by an exterior object is so powerful that it translates itself outwardly in a series of acts. We give an umbrella to Wit , when she is in a state of somnambulism; she takes it, and she immediately shivers as if she felt the approach of the storm ; then she opens it and begins to walk in the labora- tory, tucking up her skirt and looking at her feet; from time to time she jumps a streamlet. The scene is an exceedingly curious one.* *For other examples see Richer, op. cit., p, 692 et seq. REASONING IN PERCEPTION. S3 If we now compare the perception of an orange with an act of formal reasoning having as its object the death of Socrates, what analogy will be discovered? First. — It is hardly necessary to remark that these two acts belong to indirect and secondary knowledge. When we assert the future death of a living person, basing our assertion on the death of other men, our assertion anticipates the course of events; it is a prevision. In the same way, when we look at an orange and afhrm, explicitly or im- plicitly, it does not matter much, that "this is an orange," we pass beyond, by a mental act, the limit of our actual experience. This is precisely what the preceding analysis aimed at showing. The characteristics of structure, weight, taste, etc., attributed to an orange are not comprised in the visual impression which comes from the orange; to assert their existence is therefore to go beyond the sensation, to accomplish an act which depends upon indirect knowledge. Every perception resembles a reasoned conclusion ; it contains, like the logical conclusion, a decision, an affirmation, a belief, relating to a fact which is not directly known by the senses ; it is, in other words, a transition from a known fact to an unknown fact. Second. — The two acts which we are comparing have a common feature in implying the existence of certain anterior intellectual states — that is to say, of recollections. In formal reasoning, these preparatory states are called premisses. Without premisses, there can be no conclusion. Our mind 84 THE PSrCHOLOGT OF REASONING. only accepts this proposition, "Socrates is mortal," because it knows the truth of a different propo- sition, "All men are mortal." Here there is, be- sides, a distinctive characteristic of all the indirect processes of knowledge; being indirect, they neces- sarily demand a proof. It matters little whether this proof be or be not present to the mind at the moment when we make use of it ; what is sufficient and essential is that we should have known it. Thus there are many simplified acts of reasoning whose premisses are unconscious. The majority of the inferences which we make daily for the practical needs of life are of this nature. Mr. Spencer gives an interesting example. "It is stated that Mr. So-and-so, who is ninety years old, is about to build a new mansion; and you instantly laugh at the absurdity — a man so near death making such preparation for life. But how came you to think of Mr. So-and-so as dying? Did you first repeat to yourself the proposition, 'AH men must die?' Nothing of the kind. Certain antecedents led you to think of death as one of his attributes, without previously thinking of it as an attribute of mankind at large. To any one who considered Mr. So-and-so's folly not manifest, you would probably say, 'He must die, and that very shortly,' not even then appealing to the general fact. Only on being asked ivliy he must die,, would you either in thought or word resort to the argu- ment, 'AH men die, therefore So-and-so must die.' We know, according to Mr. Spencer, that the syllogism represents, not the process by which the REASONING IN PERCEPTION. 85 conclusion is reached, but the process by which it is justified; in other words, the syllogism, by con- veniently exhibiting the data of an act of reason- ing, enables us to see whether we are asserting more than we absolutely know, and whether the conclusion is really involved in the premisses, as we suppose it to be. The example quoted explains this theory. Returning now to the perception of an orange, we shall have no trouble in proving that this act demands, as does an act of reasoning, logical ante- cedents. What our eye lets us know directly is the impression of a yellow spot ; no one will maintain that we are able, apart from all experience, and by a kind of pre-established mechanism, to conclude from this sensation that there is an orange in our hand, a fruit which we may cut, eat, suck, and which quenches thirst, etc. If no experience had ever intervened, our intellect would see nothing beyond our actual sensation, and there would be no perception, in the proper sense of the word. If, on the contrary, we are able to recognize the orange, it is because our eye has received previous education ; it is because we have learned to associ- ate, on other occasions, a certain visual impression (the sight of the orange) with all the other impres- sions which we formerly experienced when we took the orange in our hands to cut and eat it. This is therefore the second point of contact between the perception of an exterior object and an act of reasoning. These two acts imply older states, recollections. These logical antecedents are 86 THE PSrCHOLOGT OF REASONING. called premisses in reasoning and anterior experiences in perception. The premiss of the reasoning analyzed is, "All men are mortal." That of per- ception might be, strictly speaking, formulated in an analogous fashion: "All spherical bodies of yellow colour and of a certain size are fruits filled with a sweet juice." However that may be, we see that perception consists, like reasoning, in the application of a recollection to the knowledge of a new fact, and ends in the generalization of this recollection. But that is not all. If in the majority of reasonings the premisses remain unconscious, in all or almost all cases of per- ception, the anterior experiences which render them possible are recalled to the mind as little. Thus, when we see a certain yellow spot, we imme- diately affirm "this is an orange;" there is no con- scious return towards the past, and consequently no allegation of proof. It is only if we throw doubt upon the accuracy of our perception that we invoke our past experience, exactly as in our every- day experiences. Third.— We proceed with our parallel to see how far it is justified. We know that the foundation of all reasoning is the recognition of a similitude; reasoning may be roughly defined as the transition from a known fact to a second unknown fact, by means of a resemblance. When we mentally read over the following syllogism, "All men are mortal; Socrates is a man, therefore Socrates is mortal," we pass from a known fact (the mortality of men) REASONING IN PERCEPTION. by to an unknown fact (the death of Socrates), by virtue of the relation of resemblance which we discern between the two facts; this resemblance forms the object of a special proposition, "Socrates is a man. ' ' There is no act of reasoning in the world which does not contain, after the manner of this example, the afidrmation of a resemblance; but this affirmation takes different forms and is called by different names: comparison, classification, recognition, etc. We even know that the school of Aristotle compares reasoning to a classification. To conclude that Socrates is mortal would be to put Socrates in the class of men, of whom mortality is an attribute. The perception of an exterior object implies a similar act of identification. In order to recognize, with the sight alone, that we have before us an orange, it is not enough that past experiences should have formed an association between a piece of yel- lowish-red colour and certain characteristics of structure, touch, taste and weight; it is necessary, in addition, that a resemblance should exist between the two experiences, past and present ; it is neces- sary that the two pieces of colour should have the same colour, the same tint. We do not generally reflect in order to assure ourselves of this resem- blance by a voluntary act of comparison ; but it is none the less true that it, the resemblance, must exis-t. Further, we are, in the majority of cases, very quick to distinguish a real resemblance from a deceptive analogy. Some authors have also compared perception to 88 THE PSrCHOLOGT OF REASONING. an operation of classifying, as has been done in the case of logical reasoning. According to them, the visual perception of an object would consist of classing the sensation which we experience in the group of analogous sensations which have formerly- been experienced. This idea has been developed at length by Mr. Spencer. In short, perception and reasoning have the three following characteristics in common : First, they belong to mediate and indirect knowledge; second, they require the intervention of truths for- merly known (recollections, facts of experience, premisses); third, they imply the recognition of a similitude between the fact affirmed and the ante- rior truth upon which it depends. The union of these characteristics shows that perception is com- parable to the conclusion of logical reasoning,* This is one of those truths which have been so fully demonstrated that they have found their way into every book. Helmholtz says in this connec- tion: The judgments by which we trace sensations back to their causes belong, by their results, to what are called judgments by induction ;f and in support of this contention, he cites the following example: "As in the immense majority of cases the excita- *We may remark that the existence of so many different definitions of reasoning; is due to the fact that each of them considers only one of the fore- mentioned characteristics. Thus, the following definition: reasoning is a transition frotn the knozvn to the tinknqwn, or again, reasoning is a demon- stration, relates to the first characteristic; the definition: reasoning is an extension of knoivledge already attained, relates to the second; and the definition: reasonijig is a classification, relates to the third. tinduction is inaccurate. In perception, the mind never rises so high as a general conclusion; it simply comes to a conclusion on the object present to the senses. It is an inference from particular to particular, and likewise, in the case where perception is aided by a considerable number of anterior experiences, it is a deduction. REASONING IN PERCEPTION. 89 tion of the retina at the external angle of the eye comes from a ray of light which reaches the eye from the nasal side, we think it is the same in every new case in which the excitation affects the same part of the retina, just as we maintain that every man who is at present living must die, because experience has taught us that so far death is the end of all men." We might extract analogous quota- tions from the works of Mill, Spencer, Bain, etc. It would be easy to follow up and renew the comparison which we have made between perception and the syllogism, by remarking that if perception is an act of reasoning, the illusion of the senses is a sophism. This deduction was made long ago ; it has even been attempted to extract the logical rule which is violated by the majority of illusions. We may cite an example, borrowing it from the class of passive illusions, which have been very carefully studied by Mr. J. Sully.* If the finger be pressed upon the outside of the lowered eyelid, a kind of luminous ring will appear. This image, which represents the end of the finger, will not be local- ized at the point where the retina has been excited, but inside and above, towards the upper part of the nose, just at the place where the luminous source which affects the retina at the place touched is generally situated. The sophism contained in the unconscious reasoning consists in taking as an abso- lute law a rule which is only valid in certain cases. Errors of this kind are frequently met with in the physiology of the organs of the senses. *0p. cit., passim. 90 THE PSTCHOLOGT OF REASONING. We may now consider it as sufficiently demon- strated that perception is an act of reasoning. We shall not therefore pause to discuss the opinion of some thinkers who insist upon drawing a line be- tween reasoning and inference, and wish to see no more than an inference in perception. According to these writers, inference would be the simple con- secution by which the mind passes from one idea to another, as when a Dutchman, traversing a town in India, expects to find a tavern in it; this operation, though a passage from the known to the unknown, would be only a pseudo-reasoning, a sketch which does not deserve the name of the finished work. But there is in reasoning, always according to the same writers, something more in the mind than this bringing together of facts. Reasoning is the reflect- ive act by which the mind adopts a proposition because it sees in it the logical consequence of other propositions which it holds to be true; so that the only rational operation is that in which all the premisses are present to the mind, and where the mind perceives the relation which binds the premisses to the conclusion.* We reject this arbitrary distinction. Inference or reasoning, it is always the same thing; we have just shown this in the case of perception, where analysis reveals the essential parts of a syllogism. How could it be maintained, after that analysis, that perception is a simple consecution? All that may be granted is that in reality certain reasonings are conscious and that others are automatic. Per- *Brochard, Logique de Stuart Mill, Revtte philos.. Vol. XII. REASONING IN PERCEPTION. 9I ception is of the second class. But great value should not be attached to this difference. Con- sciousness accompanies the physiological processes of reasoniiig, of sensation, of recollection, etc., it does not constitute them ; it is an epiphenomenon, and nothing more.* So far as quantitative experi- ments made on sensations go to prove, conscious- ness is subject to conditions of duration and intens- ity. If these conditions are realized, it exists; if not, it is wanting. But in every case it appears and disappears without disturbing the action of the nerve cells, which continues silently in the same necessary way. IV. We have just seen that the work involved in every perception is identical with the operation which consists in drawing a conclusion when the premisses are given. At the same time we made a short survey of the nature of this work. Let us go further, and we shall try to give an explanation of reasoning. But before approaching this great problem, to which this book is wholly devoted, let us pause at some preliminary considerations. We intend to give a psychological theory of reasoning. For this theory to be correct, for it to be even accept- able, it is evidently necessary that it should satisfy certain conditions, that it should fit certain psychical facts already known and considered as certain. Psychology is no longer in that state of *Ribot, Diseases of the Memory, p. "^6 (Appleton, New York), and The Diseases of Personality, Introduction (The Open Court Pub. Co., Chicago). 92 THE PSrCHOLOGT OF REASONING. infancy which every science has known and in which any one may freely erect fantastic explanations which rest on nothing. In every science which has undergone organiza- tion, a new theory has a right to be cited only when it is supported by admitted facts; if, for ex- ample, some one pretended to have discovered per- petual motion, it would be right to reject his pre- tended discovery without examination, for it would be contrary to all the laws of mechanics. Psychol- ogy also has its questions of perpetual motion. Therefore, before seeking the solution of our prob- lem, let us put it in the form of an equation, in order to determine the conditions which the solu- tion must satisfy in order to be correct. First condition. — Stuart Mill remarked that all psychological explanations, without exception, are subject to a general condition ; that of being an application of the lazvs of association by resemblance and by contiguity.'^ To explain a psychological fact is, according to Stuart Mill, to show that it is a particular case of the laws of association. We do not intend to inform the reader what is understood by these laws ; the subject is well known, thanks to the numerous analyses of English works which we possess. We may merely recall the fact that asso- ciation by resemblance is the law by which ideas, images and feelings vv^hich are alike are called up in the mind. Thus, a portrait evokes the idea of the model. We may also recall the fact that associa- tion by contiguity is the law by which two phenom- *John Stuart Mill, Dissertations and Discussions, III, loS et seq. REASONING IN PERCEPTION. 93 ena which have been experienced together tend to associate themselves in our mind, so that the image of the one recalls the image of the other. Such are the laws of association ; our cut-and-dried formulae can convey no idea of the immense number of phe- nomena which these laws explain. However, no one has the right to maintain that these laws are the only ones, and that no others exist. We cannot imagine that we already know all the laws of mind. That would be a singular presumption. So we believe that Stuart Mill was too exclusive in saying that all psychological explanations consist in reduc- ing the fact to be explained to the laws of associa- tion. What must be retained of Stuart Mill's opinion is that in psychology, as in all other sci- ences, an explanation ought to plead nothing out- side of truths which are at the same time known and established ; now, as the only psychological laws which we can at the present time consider as established are those of association, they are the only ones which we may provisionally introduce into explanations. There we have a valuable sign which enables us to distinguish at first sight a seri- ous explanation from those caricatures of explana- tions which are merely hypotheses built upon other hypotheses. Second condition. — For the psychologist every verbal proposition resolves itself into an association of images, and the demonstration of a proposition, the reasoning, is the creation of a new association. Reasoning has been very accurately defined by Mr. Spencer as "the establishment of a relation between 94 THE PSrCHOLOGT OF REASONING. two things," and he has explained, with a great amount of detail, the meaning and the range of his definition. We have already had occasion to show that in every perception there is work, and that this work culminates in a synthesis of sensations and images.* The process of perceiving an object, for example an orange, and of recognizing the existence and nature of that fruit when placed before us, consists in associating with a visual impression a certain num- ber of attributes of which we do not take direct cognizance; but to associate two groups of quali- ties, is to judge; it is, as Mr. Spencer's definition has it, to establish a relation between two things. This settled, the following question arises: How is this synthesis formed? By what process is a relation established between the two things? How do we pass from an impression of yellowish-red colour received by the eye to the image of all those attributes which characterize an orange? Or again (for we are anxious to show all the aspects of the problem), how do tve Judge that "this is an orange?" Third condition. — Mr. Spencer adds a word to the definition of reasoning already quoted. Rea- soning, he says, is the indirect establishment of a relation between two things. This adjective will be fully understood by means of an example. Let us suppose that instead of confining ourselves to looking at the orange, we took hold of the fruit and occupied ourselves in peeling and eating it. Accord- ing as w^e perform these different actions, an associ- *See pages 70 and 81. liEASOAriNG IN PERCEPTION. 95 ation becomes formed in our mind between the sight of the orange and innumerable sensations of the hand and of taste: the formation of this rela- tion is direct, produced by experience, it comes from without. On the contrary, when we perceive the orange at a distance, without touching it — that is to say, when we reason regarding our visual sen- sation — the relation which is established between this sensation and the mental image of the attri- butes is indirect, in the sense that it is not produced by actual experience, and that it is produced by the operation of other intellectual states — premisses. Let us express this fact in the precise language of psychology. What is a premiss? It is a judg- ment, an association of images. Consequently, what is a conclusion which follows from the prem- isses? It is an association of images produced by other associations. We may therefore formulate as follows the third question which arises: How can the two complete associations forming the premisses unite to form a third, that which constitutes the conclusion of the reasoning? We possess the touchstone with which we may make sure whether a psychological theory of reason- ing is true or false. Let us try this criterion. Very few of the existing theories of reasoning are in harmony with modern ideas and merit discus- sion. The spirtualistic French school, which has on many questions adhered to the old doctrine of entities, generally explains reasoning by a faculty of reasoning; some supporters of this school are not 96 THE PSrCHOLOGT OF REASONING. content with this purely verbal explanation, but they confine themselves to maintaining that reason- ing is a simple, irreducible and consequently inex- plicable property. It is to be regretted that M. Taine, in his magnificent work On Intelligence, gave us a theory of knowledge instead of a psychol- ogy of reasoning. In Germany, Wundt places rea- soning at the basis of the psychical life ; he makes it the foundation of all our thoughts, and goes as far as to say that we might call the mind "a thing which reasons." Thus he tries to discover reason- ing even in the primitive and elementary fact of the psychical hfe, in sensation. But when it comes to taking the mechanism of reasoning to pieces, bit by bit, to explain it according to known laws, a gap is visible in his work. As far as we are able to judge, in the light of M. Ribot's analyses, which are always masterpieces, Wundt has not given us an explanation of reasoning. In England, Stuart Mill concerns himself almost exclusively with the logic of reasoning, he leaves psychology alone; and we know that there is as much difference between psychology and logic as between physiology and hygiene. Alexander Bain, who systematically reduces all mental states to a combination of the la\i/s of association, touches several times upon the question which engages us; but his thought re- mains vague and irresolute, and, yielding to his habit, he describes instead of explaining.* Only in Mr. Spencer's work do we find a true theory of reasoning. *See especially, in his excellent book on The Senses and the Intellect, pages 524 et seq. REASONING IN PERCEPTION. 97 In this case the theory is as complete as could be wished, for it starts from the most elevated type of reasoning and reaches the simplest, including in its immense span compound quantitative reasoning, simple and imperfect quantitative reasoning, perfect qualitative reasoning, imperfect qualitative reason- ing, reason in general, perception, and the feeling of resistance. The author has tried to prove that the process which the philosopher follows in his longest and most complicated reasonings is that by which incipient consciousness strives to become thought; that, in a word, a unity of composition exists among all the phenomena of the intellect. What is this unity? The whole study of reasoning may be summed up by defining it as "a classifica- tion of relations." But what does the word classi- fication signify? It signifies the act of grouping together like relations. To deduce a relation is to think that it is like certain others.* Before this theory is discussed it must be made clear. We shall do this by quoting from the author some types of reasoning, and by showing how the idea of a classification of relations throws light upon the mechanism of these operations. Let us take as an example an "imperfect quali- tative reasoning," which treatises on logic com- monly give as a syllogism. When we say, "All horned animals are ruminants; this is a horned animal, therefore this animal is a ruminant," the mental act indicated is, according to Mr. Spencer, a cognition of the fact that the relation between the *Half of the second volume of The Principles of Psychology is devoted to the development of this question. THE PSrCIIOLOGT OF REASONING. particular attributes in this animal is like the rela- tion between the homologous attributes in certain other animals. It may be symbolized thus: (Tlic aUril)iites consti- tuting a horned ani- A mal.) (coexist with) (The attributes consti- tuting a ruminating animal.) B (The attributes consti- a tuting this a horned animal.) is like-| (coexist with) (The attriljutes consti- b tuting this a ruminat- ^ ing animal.) "The relation between A and V> is like the rela- tion between a and b;" such is the formula which, according to the author, really represents our log- ical intuition. It will be noticed that reasoning thus understood becomes a true proportion, with four terms, a kind of rule of three from which the idea of quantity is excluded. Stuart Mill has reproached Mr. Spencer for making reasoning an operation in four terms, and he has maintained that in reality only three exi.st. Thus, to transfer the controversy to the preceding example, Stuart Mill has remarked that the reasoning attributes to a certain' animal which has horns the savic attributes (constituting the ruminating aniiTial) as to all the other animals which have horns; consequently, the two terms indicated by the letters W and b make only one, they are the same; three terms exi.st and not four. Mr. Spencer has replied that as these attributes do not belong to the .same animals, but to distinct though similar animals, the attributes also ought to be distinct. The .solution of this difficidty is easy to find; it seems to us that Mill is I^EASO.VnVG IN PERCEPTION. 99 right. He would hav-e been able to repty to Mr. Spencer: Ever\' horned beast has distinct attri- butes which make it a ruminant, but the general idea which we have of these attributes is common to these animals; it is the same for all. And thus we succeed in reducing the terms of the reasoning to thr ee * That, however, is a trifling matter. Let us admit for a moment the existence of the four terms. It ma)- be granted that reasoning is a classification of relations; but the relations must be formed be- fore they can be classed, for they <^o not exist before being formed, and we cannot compare what tioes not exist. The curious thing is that this im- portant question is hardly touched upon by Mr. Spencer, anci yet he was the first to recognize that reasoning consists in the establishment of a relation. The few words which he has written on this sub- ject, as if by the way, relate to another example. f Analyzing the following syllogism, "All crystals have planes of cleavage; this is a crystal, therefore this has a plane of cleavage," he inquires how our mind is able to pass from the perception of an indi- vidual crystal to the idea of a plane of cleavage; and he prefers to sa)-, in order to explain the estab- lishment of a relation between these two things, which is the essential difficulty of the question: "Before consciously asserting that all crystals have planes of cleavage it has already occurred to me that this crystal has a plane of cleavage." But then, it may be objected, everything is done; the *Spencer, Princit'lcs of Fsycholog^y, Vol. II, p. 69. iOp. cii.,p.i)';, Vol. H. lOO THE PSrCHOLGGT OF REASONING. work of reasoning is accomplished, the relation is established, and it is precisely all this which required explanation. Mr. Spencer himself recog- nizes this, for he calls this operation, which he assumes to be effected without explaining its gen- esis, a primary or provisional inference. "This act is simple and spontaneous," he says, "resulting not from a remembrance of the before-known like rela- tions, but merely from the influence which as past experiences they exercise over the association of ideas."* Therefore we see that when it comes to the decisive moment, the theory disappears; it can- not be declared to be either true or false, for it does not really exist. We have still many other objections to offer. We might ask what, in this comparison of relations, the old relation, that which takes the place of premisses, can add to the new and inferred relation. When I assert that a relation exists between the crystal which I hold and a plane of cleavage, I find, it is true, a confirmation of what I assert, in repre- senting this old relation to myself: All crystals have planes of cleavage. The general rule proves the particular case. But it is precisely this which wants explanation. We have just shown this in stating the equation of a theory of reasoning; the reader will recollect that we made this point the third condition which a theory of reasoning must fulfill in order to be correct. It must be explained, we have said, how a conclusion follows from its premisses; in more accurate language, it must be *0p, cit.. Vol. II, p. 102. JRBASONIJVG IN PERCEPTION. lOl shown how an association between two terms can be formed by the medium of former associations. But Mr. Spencer's hypothesis is powerless to solve this question. What does he tell us? That the mind, after having formed (it is not known how) a relation between a and b, compares it to a before-known relation between A and B. But what can follow from this intuition of a resemblance between the two relations? How can the comparison of the two add to the bond which already unites the terms a and b? This is a question of mental mechanism which has to be solved. Mr. Spencer does not solve it, he does not even suspect it. It is one of the characteristics of the theory we are discussing that it does not touch this question. Mr. Spencer confines himself to proving that the idea that all crystals have planes of cleavage confirms the partic- ular conclusion, this crystal has a plane of cleavage ; but, once more, this is merely stating the question. It would be necessary to explain this confirmation of the particular relation by the general relation by introducing the laws of association. We are sorry to have to deliver such a judgment on a part of the work of a thinker who has done so much for psychology; but it is a duty to judge theories in themselves, without taking into account the fame of those whose namics are associated with them. We shall, in our turn, approach the problem of reasoning, putting forward some observations on a mental law to which we shall often appeal, the law of resemblance. CHAPTER IV. THE MECHANISM OF REASONING. The action of resemblance on the phenomena of the mind has been, so to speak, recognized in all times; it has never been very difficult to discover that one idea suggests a like one. Mr. Bain, who has devoted a long chapter, full of facts, to association by resemblance, enunciates in the fol- lowing terms the law which governs this association : "Present actions, sensations, thoughts or emotions tend to revive their like ■bsc^.ow^ previous impressions or states."* This is a very wide formula, for it includes not only ideas, but emotions and actions; nevertheless, it seems to us to be incomplete upon a most important point. The reproductory action of resemblance — the attraction of sameness — is a common and superficial effect, known to us since the days of Aristotle ;f resemblance has in reality a second effect, quite as important as the first — that of fusion. Alongside the law of suggestion and of recollection by resem- blance, we may place the Law of Fusion. It may be enunciated as follows, the demonstra- *Bain, The Senses and The Intellect, p. 463 ; J. Stuart Mil', Examina- tion of Sir William Hamilton's Philosophy, p. 225; Cf. Ribot, La psycho- logie anglaise contemporaine . fOn this subject Hamilton's Dissertation at the end of his edition of Reid, may be consulted. 102 THE MECHANISM OF REASONING. 1 03 tion being left for later consideration : "When two like states of consciousness are present to our. mind simultaneously or in immediate succession, they become fused together so as to form a single state." Thus, when two sounds of the same pitch and the same timbre vibrate at the same time, the most practiced ear does not dissociate them ; only a single reinforced sound is heard ; each sound loses its individuality in a single resultant. If the two states of consciousness are exactly alike, the fusion is com- plete ; if they present only an imperfect resemblance, implying a partial sameness, the fusion is partial. The fiision of like sensations. — The best illustra- tion of our law as regards sensations is furnished by the sensations of touch, in Weber's experiment. This experiment shows us the fusion of like sensa- tions ; they fuse so thoroughly that a person who has not been told beforehand that he is receiving two sensations produced by two distinct excitations believes, while he experiences only a single sensation, that his skin is bearing only a single pressure. But this phenomenon touches upon a much dis- cussed problem in physiology, upon which we must first of all say some words of explanation. Among all the senses, touch is the one which occupies the largest surface ; while the special senses, sight, hearing, smell and taste, are confined to ex- tremely small parts of the organism, that of touch is found over the whole extent of the skin and even on some mucous membranes; the nasal fossae, the conjunctiva, the buccal cavity, the two extrem- ities of the digestive tube, and the urethral canal I04 THE PSrCHOLOGT OF REASONING. give us sensations of contact. This wide diffusion of the sense of touch over the surface of the body is explained by the fact that touch is the funda- mental and primitive sense from which the special senses have been derived by a progressive differenti- ation, and which perhaps will, in the course of time, give rise to the formation of new special senses. The sense of touch is not equal all over; certain divisions of the general epidermis display a delicacy superior to that of the others. For ex- ample, we know that the tactile sensibility is dull on the middle of the back; it is keener on the hand, keener still on the tips of the fingers; the highest degree of sensibility is reached at the end of the tongue. Weber succeeded in measuring these differences in sensibility by employing a pair of blunt compasses, the two points of which he shifted over the surface of the body. He found that on the middle of the back the two points are not felt double until they are thirty-nine lines apart (a line =0.88 inch); when closer, the two points produce only a single sensation. On the chest the necessary distance is twenty lines ; on the thigh, sixteen ; on the lower part of the forehead, ten; on the palm of the hand or the end of the nose, three ; on the edge of the lower lip, two ; on the tip of the index finger, one; on the point of the tongue, one-half. These experiments in measurements have given rise to a new problem. It has been asked why two compass points produce, according to their distance apart and the region of the body on which they are placed, sometimes two sensations, sometimes one. THE MECHANISM OF REASONING. 105 Two explanations have been proposed. The first, simple after the manner of all a priori views, consists in saying that where two points are felt, each of them has separately excited a nerve fibre, and that, on the other hand, when we feel only a single point, the points of the compass have excited only a single fibre. In every case we experience as many sensations as there have been nerves excited. A trace of this explanation remains in the language, in the term ccrcle dc sensation. If one of the two points of the compasses be pressed on the skin, and if it be tried up to what distance from the first point the second fails to produce a new sensation, an area is thus circumscribed which has the form of a circle or of an ellipse. This area, being capable of receiving only a single sensation, corresponds, according to the theory, to the territoiy of one nerve fibre ; it is called the circle of sensation. This explanation contains a part of the truth. There is no doubt that the portions of the integu- ment whose sensibility is very delicate are richer in corpuscles of touch than the portions whose sensi- bility is dull. But this is a very different thing from admitting that every circle of sensation is, as has been said, an anatomical unit, the territory of a single fibre. There are places where the points of the compass may be separated by more than a dozen nerve papillae without producing any more than a single impression. We may add that the limits of a circle of sensation vary strikingly under the influence of attention and of practice ; if a circle really corresponded to the province of a single fibre, Io6 THE PSJ'CHOLOGT OF REASONING. this would be an invariable unit. Finally, there is a more conclusive fact than all the others. If two circles of sensation, whose circumferences are tangential, are drawn upon a person's forearm, and if one of the points of the compasses be placed in one circle and the other in the other, the two being brought as near together as possible, the person undergoing the experiment will experience only one sensation; in order to produce two, the points must be separated by the whole diameter of a circle. If it were true that each circle was supplied by a special fibre, it would be sufificient for the two points to be placed upon any points whatever in the two circles for the person to feel both of them. The second explanation is known under the name of the tJieory of nerve fields. It is observed that for two sensations of touch to be distinguished there must be between the excited points on the skin a certain space, a certain number of nerve ramifications, a nerve field. Only this distance is necessary, and it is suf^cient. Why is it so? Be- cause, it is said, two things can only be distin- guished if something separates them. The excita- tion of the two nerve fibres can only produce two distinct impressions if these two fibres are separated by unimpressed nerve elements. These elements, whose role is to divide the two sensations, are represented by the distance apart of the two points of the compass. This pretended explanation seems to us to be simply a tautology ; it af^rms the necessity for the separation of the points, which is a fact of observa- THE MECHANISM OF REASONING. lOj tion ; but it is not apparent what can be the role of the intervening nerve fibres, since nothing produces an impression upon them. The theory of nerve fields is powerless to explain this. The explanation which I propose to substitute for the preceding ones may be summed up in a few words. I assume that every point on our epidermis has a special way of feeling; the quality of the sen- sation varies with the region of the skin ; for ex- ample, when the forehead, then the cheek, chin, neck and the nape of the neck are pressed by the finger, a different tactile sensation is produced every time. This variation always takes place in a con- tinuous manner from one point to another; if we chose two points close together it might happen that the difference between the two sensations would be too slight to be perceived, and that the two sensations would behave practically as if they were identical. The distance at which the two sen- sations may be distinguished in consciousness is not uniform over the whole body, for the local quality of each sensation does not vary equally all over. This being admitted — and we shall shortly enumer- ate the arguments which prove our hypothesis — what will happen? By exciting two points on the skin with the compasses, we may produce at pleas- ure, according to the distance apart of the points and the region of the skin, two different sensations or two similar sensations; they will be different when the points on the skin are far enough apart for their difference of sensibility to be appreciable; they will be ahke when the points selected are suf- Io8 THE PSrCHOLOGT OF REASONING. ficiently near to each other for their sensibihties to appear the same in kind. Now, in the case of two different sensations, the subject will feel the two points distinctly; in the case of two similar sensations, these sensations will become fused into one, and the subject will feel only one point. Weber's experiment would be explained, accord- ing to this hypothesis, by the fusion of similar sen- sations; it would be an illustration of the law of fusion. But what must be added to demonstrate the truth of this hypothesis? Two things must be proved : First. — That the sensations produced by the two points of a pair of compasses are of different quality when the subject perceives the two points. Second. — That the sensations produced by the two points of a pair of compasses are of the same quality when the subject perceives a single point. Lotze, Wundt, Helmholtz and others in Germany have attributed a difference of sensibility to the different regions of the body. This is what is called the tJieory of local signs. We shall choose one, the most striking, from among the proofs of this theory : it is derived from the phenomenon of localization. When we touch a person on any part whatever of his body, he feels and at the same time he localizes the excitation. This knowledge of place is not innate; it is acquired. It is formed, in all prob- ability, in the following manner: We have learned by experience that when we feel a certain tactile sensation, a pressure is produced on the arm ; a THE MECHAiVISM OF REASONING. 1 09 certain other sensation corresponds with an action on the toe, and so on. In the course of time we have connected a definite sensation with the sight of our arm, another with the sight of our toe, and finally each different sensation with the sight of a different point on our skin. When we come to press, prick or pinch our body, the sensation proper to the part affected awakens the ocular image of that part by the mere power of association. It is a mental law that when two sensations have been experienced in contiguity they adhere in such a way that the one presented suggests the other. In the present case the suggestion is effected so rapidly that the visual image of the part touched follows the tactile sensation immediately. Localization is nothing else. As regards the position of the point touched, it is given us by our muscular activity. This explanation of the genesis of the sense of place always assumes one thing: that two sensations of contact which are referred to two different parts of the body both possess a local sign which distin- guishes them and prevents them from being con- founded with each other. Suppose all our sensa- tions of contact were absolutely uniform. A per- son pricked on the finger will not-know whether it was on his finger or his toe, for if his toe had been pricked he would have experienced the same sen- sation. For one sensation of contact to become associated with the sight of the finger, and another with the sight of the toe, it is absolutely necessary that the two sensations be different ; otherwise they will be confounded with each other, and the sensa- no THE PSrCHOLOGT OF REASONING. tion whose seat is at the finger will be able to sug- gest indifferently the ocular image of quite another part of the body. In short, localization implies distinct sensations. This fact puts us in a position to know when the two sensations produced by the compasses are sim- ilar or different. Are they susceptible to being localized in a distinct manner? Then they are different. Are they not susceptible of distinct localization? Then they are similar. By making use of this criterion, we find that in every case in which the two sensations are felt double the subject can localize them, which proves that they are of different natures. For example, I press the two points of my compasses transversely on a person's forearm, the points being thirty-nine lines apart, the distance necessary for the subject to feel each point separately. Then I lift the two points up alternately, asking the person, whose eyes are shut, to inform me if it is the right or the left one he continues to feel. He replies correctly every time; he localizes exactly. This is plain proof that each of these sensations differs a little from the other. Thus in the case where the sub- ject perceives two points, there are two different sensations, as is proved by the possibility of distinct localization. Conversely, we have to investigate if it is pos- sible for the subject to give a different localization to two sensations which, simultaneously produced, have the effect of a single sensation. We try experimentally how far apart we may put the two THE MECHANISM OF REASONING. m points without their ceasing to be confounded with each other, and we mark with ink the points on the epidermis at which they are placed. It is always well not to go as far as the maximum dis- tance, for it varies a little during the course of the investigation, merely by attention and exercise; it might therefore happen with the maximum dis- tance that the two sensations, which were at first similar, became in a moment different, a condition of things which would disturb the experiment. After these preparations, we excite alternately the two points marked with ink, asking the subject to state, with his eyes shut, upon which one the instrument is placed. The subject does not succeed in this, or, if he tries to localize, he does so with alternate success and failure, which proves that he is guessing. This inability to localize the two sen- sations can depend upon only one cause, the sim- ilarity of the two sensations. It is therefore true that the experiment with the compasses gives us an example of the fusion of two similar sensations. This is all that we wished to show.* In the preceding experiment the sensations which are fused together are exactly, or almost exactly, alike, and the fusion resulting from their being brought together is total. Let us give an example of partial fusion. A partial fusion often exists in a series of sensations which succeed one another, and each of which resembles, in part only, *For further details I may refer to my article on the Fusion des sensa- tions semblables {Revue j>hilosophiqMe, September, 1880). 112 THE PSrCHOLOGT OF REASONING. that which precedes and that which follows it. This is what occurs in the zootrope, thaumatrope, phenakistoscope, dedaleum, cinematograph, etc. These scientific toys are designed to produce a series of impressions on the retina of the observer, representing the successive phases of any periodic movement, for example, a man who juggles with his head. Each figure in the zootrope, taken separately, differs very little from its neighbour on the right and on the left; their resemblance may be ex- pressed by the following letters abc, bed, cde, def, efg, fgh, etc., which indicate the portion common to two successive impressions. When the toy is put in motion and its rotation is sufficiently rapid, the impressions become fused together by their common points and give us the illusion of a single person, always the same, who makes the move- ments. The study of the mechanism of this illusion is the more interesting because it artificially repro- duces what occurs every time that we perceive a body undergoing changes of form or position, for example, a trotting horse.* We prefer to collect facts rather than linger over explanations which will come of their own accord. Let us confine ourselves to anticipating a possible objection by showing that the fusion of zootropic images is effected in the brain and not, as one might believe, in the retina. This is proved, first of all, by the fact that the consecutive visual *CliHoid has, by extending the idea of the zootrope, denied that the world can be continuous. THE MECHANISM OF REASONING. 113 images which are produced in this fusion have a cerebral seat (see above, page 44). In the second place, there is the more direct proof that the fusion is not produced en bloc, but only between the sim- ilar portions of the images, which implies a power of analysis which is certainly wanting in the retina. TJie fusion of similar images. — Images fuse together like sensations, a fact which is understood once their nature is known, for they are revived sensations. It often happens that a succession of images, partially similar, passes across the field of the mind, producing appearances of transformation comparable to those of the zootrope. One of Mr. Galton's correspondents, the Rev. George Hensiow, sees, every time he shuts his eyes and waits a short time, the clear image of some object. This object changes its form for as long as Mr. Hensiow watches it. It is noticed, in studying the series of successive forms, that the passage from one to the other is supplied sometimes by relations of con- tiguity and sometimes by relations of resemblance. In one of these experiments the following images were seen: A cross-bow, an arrow, a person shooting the arrow, his hands alone being visible ; a flight of arrows completely occupying the field of vision ; falling stars ; large flakes of snow ; a land- scape covered with a sheet of snow ; a rectory with its walls and roof covered with snow ; a spring morning, with a brilliant sun, and a bed of tulips; the disappearance of all the tulips with the excep- tion of one; the single tulip becomes double; its petals fall off rapidly, there is nothing left but the 114 THE PSrCHOLOGT OF REASONING. pistil; the pistil enlarges, and the stigmata change into three branching brown horns; a knob; the knob bends and becomes a stick; then a sort of pin passing through a metal plate, and so on. The experimenter has sometimes succeeded in com- pleting what he calls a "visual cycle" — that is to say, returning to the original image and going through the same series of forms anew. These visions recall that of Goethe, in whose case the cycle was shorter. "When I closed my eyes and depressed my head," relates the German poet, "I could cause the image of a flower to appear in the middle of the field of vision ; this flower did not for a moment retain its first form, but unfolded itself and developed from its interior new flowers, formed of coloured or sometimes green leaves. These flowers were not natural flowers, but of fan- tastic forms, although symmetrical as the rosettes of sculptors. I was unable to fix any one form, but the development of new flowers continued as long as I desired it, without any variation in the rapidity of the changes." It is plain that the transformation of the imag- inary object is produced by a succession of images. But it is important that the nature of this succession should be clearly understood. The images are not simply substituted one for another, the last to arrive expelling the preceding one ; if things occurred thus, we would have distinct images replacing each other, and not a single image which is metamor- phosed. It must be understood that each of the images is fused with the preceding one by virtue of THE MECHANISM OF REASONING. 1 15 the common points which they offer, and that, besides, the two successive images co-exist during a very short instant. Thanks to these two condi- tions, the two images form a whole and give the appearance of a single image undergoing modifica- tion. The hallucinations of the insane often present the same evolution of forms. Magnan relates that an alcoholic inebriate saw upon the wall cobwebs, ropes, nets with contracting meshes; in the middle of these meshes and strands, black balls appeared, which enlarged, became smaller, took the form of rats, cats, passed across the strands, leaped upon the bed and disappeared.* In rarer cases the metamorphosis requires years. A young girl who had become insane in consequence of an attempt to assassinate her, continually saw the fist and the arm of the individual who had attempted to kill her. Now, the disease following its course, the hallu- cination underwent a curious transformation. The image which was seen by the young girl became modified thus: Two eyes appeared on the fist of the assassin, his arm became excessively long, and finally the hallucinatory image changed into a serpent. f In other cases the outline of the hallu- cination remains constant, but the dimensions change. In an old observation by Beyle, a patient saw an ordinary cobweb, which grew to the point of filling the whole of his room and suffocating him. Dreams supply innumerable examples of *Magnan, De Palcoolisme, p. 56. tMax Simon, Le monde des reves, p. 118. Il6 THE PSrCHOLOGT OF REASONING. these kinds of transformation ; sometimes two dis- tinct persons are seen blending into one; or the same person changes his physical personality, etc. The dream is the true type of metamorphic hallu- cinations.* We mention these morbid cases because the phenomenon which we are studying is therein magnified and more easily examined. But we also meet excellent examples of the fusion of images in the normal operations of life. According to Hux- ley, the formation of general ideas would be effected by the union, the fusion, the coalescence of several images of individual objects; and in order to express his thought better, the naturalist-philos- opher makes use of an ingenious comparison, drawn from the Composite Portraits which we owe to Mr. Francis Galton's invention.f "This mental opera- tion may be rendered comprehensible, ' ' says Huxley, speaking of the generalization of an image, "by con- sidering what takes place in the formation of com- pound photographs — when the images of the faces of six sitters, for example, are each received on the same photographic plate, for a sixth of the time requisite to take one portrait. The final result is that all those points in which the six faces agree are brought out strongly, while all those in which they differ are left vague; and thus Avhat may be termed a generic portrait of the six, in contradistinction to a *J. Sully, op. cit., p. 163; and Maury, Sommeil et reves, p. 146. M. Delboeuf has compared the metamorphoses in dreams to dissolving views: " It is," he says. " as if we projected two pictures on the same screen, and at the same place, by means of two magic lanterns, and illuminated one while the other was being extinguished." i^Revue philos., June, 1880). This ex- planation confirms ours, it does not destroy it. tGalton, Inquiries into Human Faculty and its Development (Ap- pendix: Generic images') . THE MECHANISM OF REASONING. 117 Specific portrait of any one, is produced.* This beautiful invention has, it appears, already pro- duced brilliant results. By combining in a single photograph five medals representing Cleopatra, which, far from giving an idea of the beauty of that celebrated queen, had a hideous appearance, a much more pleasant composite portrait was obtained. It is probable that the points of resemblance be- tween the different likenesses were reinforced in this resultant, and that the points of difference remained unaccentuated {fious)\ so that we may reasonably maintain that the composite portrait has a better chance of being like the model than its components. Photographs of individuals belonging to the same classes have also been combined by this method, and thus certain types, as for example, the swindler type, have been obtained. This method will perhaps become useful to criminal anthropology in the future. Huxley's comparison between these composite photographs and concepts has been accepted by many psychologists; it has been regarded as very probable that the generalization of an image is formed in the mind like the generic photograph on the sensitive plate, by the superposition of particu- lar impressions. We may add a corroborative argument. M. Pouchet has remarked that the con- secutive images of his microscopic preparations which, as we have already seen, sometimes ap- peared to him after a long interval, do not represent any preparation in particular, but are like the vicait *Huxley, Hume {English Men of Letters Series), p. gj. Il8 THE PSrCHOLOGT OF REASONING. of a series of preparations of the same kind. This fact tends to show that the generic image is the result of the coalescence of several particular im- pressions united into a single one. However, it would be very unscientific to explain a mental operation by a comparison with a purely mechanical phenomenon, unless that com- parison implicitly assumed the existence of a prin- ciple of fusion. The formation of generic images is explained by the principle of fusion; particular impressions, becoming fused together, form a generic image because their common parts are fused together and are brought out strongly, while the parts which differ remain separate and become vague. The comparison between the generic image and the composite photograph is only accurate in so far as it illustrates this mental law ; taken literally, it is not rigorously exact. If the eye of a man, says Galton, be put in the place of the object glass of the apparatus used in obtaining composite portraits, the image which would be formed in his brain would not be identical with the composite portrait. For, contrarily to the photographic effect, the physiolo- gical effect of an impression is not proportional to its duration or its frequency; we know that, accord- ing to Weber's law (a disputable law, whose fault is that it is too precise), the sensation varies as the logarithm of the stimulus; in order that the sensa- tion may follow an arithmetical progression, the stimulus must follow a geometrical progression. We may also add the disturbing effect of attention, THE MECHANISM OF REASONING. I19 of emotion, of preconceived ideas, and of a great number of other factors, which prevent the mind from fusing several images together with the exact- ness of a photographic plate. We have given a sufficient number of examples to make it clearly understood in what the fusion of sensations and of images consists. It seems impossible that a phenomenon so easy of observation should have passed unnoticed. Among the authors who have alluded to it we may first of all mention Herbert Spencer. Defining a state of conscious- ness, this author says that it is "any portion of consciousness which occupies a place sufficiently large to give it a perceivable idividuality ; which has its individuality marked off from adjacent portions of consciousness by qualitative contrasts, and which, when introspectively contemplated, appears to be Jiomogencous.'''^ It follows from this definition that if the portions adjacent to the state considered are not different, they form part of the same state; but to say that is to implicitly recognize the prin- ciple of fusion. Later on Mr. Spencer adds: "The requisite to the existence of two feelings is some difference.' '\ Therefore, if there is no differ- ence, there is a single state, that is to say a fusion of the two states into one. These few quotations show us that Mr. Spencer has observed, at least in passing, the phenomenon of fusion, but without comprehending its importance. Mr. Bain has made a few remarks on the same phenomenon. "In the case of perfect identity *Spencer, Principles of Psychology, Vol. I, p. 164. to/, cit.. Vol. I, p. 167. I20 THE PSrCHOLOGT OF REASONING. between a present and a past impression, the past is recovered and fused with the present, instantane- ously and surely. So quick and unfaltering is the process that we lose sight of it altogether; we are scarcely made aware of the existence of an associat- ing link of similarity in the chain of sequence. When I look at the full moon, I am instantly im- pressed with the state arising from all my former impressions of her disc added together."* The description refers to a case which we shall consider presently : the fusion of a sensation with an image. Elsewhere the same author speaks of cases in which we are cognizant of an identity without being able to say what the identical thing is, as for example when a portrait gives us the impression that we have seen the original, without our being capable of saying what the original is. The iden- tity has struck our mind, but the restoration is not made. Everybody knows that very singular feel- ing of "already seen." Mr. Bain explains it by the absence of recollection of the different parts of the object identified. In fact, in order that the mind may perceive the resemblance between two images, they must differ a little; if they do not, they become added together and form a single image, Lotze expresses the same idea with a lourdeur which is quite German: ''We should know nothing whatever of this fact, the reproduc- tion of a former a by the present A, if the two were simply present, with no distinction between them, at the same time. To know the present A *Bhilosophique. Vol. I, No. 3. (New series.) 123 THE PSrCHOLOGT OF REASONING. often heard. "If the words which are sung in the Italian opera," he said again, "are not pronounced strongly, the listener seated at the back of the the- atre receives the impression of vowels and musical modulations only; but he does not hear, and there- fore does not recognize, the words pronounced. If he then opens the book of words of the opera, he will, by following them with his eyes, hear quite distinctly these same utterances which he was unable to catch a moment before. What has hap- pened to him is this. The sight of the characters before his eyes, forming not only the visual sensa- tion of the moment, but images of sensations of the same kind which he has experienced in learning to read Italian, the sight of the written words awakens in him the sonorous and acoustic images of the words pronounced, and the images of the sounds reinforcing in his mind the too feeble impressions received from the stage, the result is that he hears distinctly."* Here our quotations cease. They suflfice to show that our study of the fusion of similar states of consciousness is altogether without originality, for this phenomenon has been perceived by a num- ber of authors. While not wishing to exhaust this subject, we desire to say a few words on its physiological aspect. We have this moment seen the role re- semblance plays in the sphere of sensations and images: it suggests and fuses. The first effect is better known than the second. However, we *Fhilosophie des detcx Ampere, p. 37. THE MECHANISM OF REASONING. 123 believe that we have placed the fusion of similar sensations and also of similar images beyond doubt. We even infer, by means of induction, that this phenomenon occurs every time that we perceive a resemblance, from the insignificant act which makes us recognize a friend, to the flash of genius which discerns an identity between the most remote phe- nomena, such as the fall of a stone and the force which urges the moon towards our globe. It remains to discover whether there exists a physiological phenomenon which might be consid- ered as the basis of this double property of resem- blance. We may assume as exceedingly probable that two states of consciousness which resemble each other totally or in part, must in general involve the entering into activity of the same fterve elements, cells and fibres, totally or in part — that is to say, to the same degree. This hypothesis appears to us to be a necessary consequence of the principle of cerebral localizations, according to which all im- pressions of the same kind affect the same part of the brain. But it is by no means necessary that the rule should be made absolute ; we are inclined to admit that there exist in the brain non-differen- tiated territories, where even similar impressions may affect distinct points. After having made this restriction in our hypothesis, we may mention some of the numerous facts which militate in its favour. We all know the involuntary mistakes which make us pronounce one word instead of another. Lewes records that he was one day relating a visit 124 THE PSrCHOLOGT OF REASONING. to the epileptic hospital, and, intending to name the friend, Dr. Bastian, who accompanied him, he said, "Dr. Brinton," then immediately corrected this with "Dr. Bridges;" this also was rejected, and Dr. Bastian was pronounced. "I was," he says, "under no confusion whatever as to the per- sons, but, having imperfectly adjusted the group of muscles necessary for the articulation of the one name, the one element which was common to that group and to the others, namely B, served to recall all three." M. Ribot, from whom we borrow the preceding quotation,* has made an analogous obser- vation on mistakes in writing. Wishing to write ''doit de bonnes,'' he wrote ''donne;'" wishing to write ' ' ne pas /aire une pai't, ' ' he wrote ' ' ne part faireJ" We may again remark that in patholog- ical paraphrasiSs and paragraphias the confusion is often produced also by an identity of letters or by consonance. All this is explained, as the authors just quoted observe, by supposing that the same nerve elements enter into different combinations, and that for example the names of Bastian, Bridges and Brinton correspond to complexus of cells which have a com- mon element, the element which corresponds to B. Thus the psychical quality of the resemblance would find its anatomical counterpart in an identity of seat. A phenomenon analogous to paraphrasia may be produced in oneself at will by setting one- self the problem of finding a proper name which one knows but which is not before the mind at the Diseases of Memory, p. 29. (Appleton, N. Y.) THE MECHANISM OF REASONING. 1 25 time. Experimental psychology may thus be studied without a laboratory. One day I tried to recall to mind the name of one of my friends to whom I wished to write a letter; this friend is called M. Truchy. I did not succeed in finding his name again immediately. I passed through the follow- ing intermediate steps, which I noted down accord- ingly, for they afford a beautiful example of para- phrasia: Morny M.ouchy Suchy Qruchy T7-uchy At each efifort of memory I gained one or two correct letters. The course of the experiment seems to show clearly that the letters common to the series of names involve the excitation of the same nerve elements.* We may therefore accept as a very likely hypothe- sis that the resemblance between two states of con- sciousness generally has its physiological counter- part in an identity of seat of the nerve process. This hypothesis has moreover been already pointed out by Mr. Spencer. Every image, he says, tends to aggregate with like images by virtue of the iden- tity of their cerebral seat. We may now make our deductions. First of all, it becomes possible to explain the suggestive action of resemblance physiologically. That every *Many other proofs might be mentioned. For example, repetition strengthens the association of two images, or of two movements; how could that Be explained without admitting that the same nerve elements receive impressions at every repetition? etc. 126 THE PSrCHOLOGT OF REASONING. state of consciousness has the property of reviving those similar to it, is due to the complexus of cells which correspond to the excitative state and to the state excited having common points, by which the nerve wave flows away from the first group of cells into the second. It is equally easy to understand the fusion of two similar states into one, since they have a numerically single nerve element as their basis. This hypothesis has a second advantage ; it explains how a resemblance between ideas is effect- ual even when it is not recognized by the mind. Psychologists are asked what may be properly understood by a resemblance which would not be perceived. Resemblance, it has been said, implies a mental comparison, and when this comparison is absent, when there is no consciousness, the resem- blance can no longer exist (Penjon). The true solution of the difficulty seems to us to be as follows : It is true that there is no resemblance without the consciousness of the resemblance, for the two things are in reality only one. But consciousness is only an epiphenomenon, superadded to cerebral activity, and capable of disappearing without the corre- sponding nerve process being altered. Two similar images succeed each other in our mind. It matters little whether we did or did not notice their resem- blance, for, being similar, they will put a common cell element in vibration. This identity of seat will be sufficient to produce all the results which are produced by a resemblance which is recognized and judged by a conscious comparison. THE MECHANISM OF REASONING. 127 Thus it happens that an image suggests one sim- ilar to it, without consciousness participating in the act. Is it not, moreover, in this way that sugges- tion by resemblance operates? Like automatically evokes like ; when the act is accomplished, reflexion intervenes to give an account of what has happened, and it is only then that we discover the existence of a resemblance in the chain of ideas. M. Pilon has developed the same idea with his usual lucidity. "We must distinguish," he says, "between associa- tion by resemblance and the perception of the resemblance. It is not by means of the relation of resemblance perceived between two ideas that one of these ideas may suggest the other; for this percep- tion of resemblance implies that the two ideas are present to the mind, and consequently that the association is already formed. To say that resem- blance is an element in association is simply to say that one idea has the property of suggesting another idea which the mind then recognizes, by means of the faculty of perceiving relations, as similar to the first." {Op. cit., p, 194.) Another deduction of the same kind as the pre- ceding one is that the formation of general ideas must take place without the intervention of the self, in the same manner as suggestion by similar- ity and for the same reasons, by the sole virtue of the images raised ; or, in more accurate terms, by the effect of the identity of seat of the particular impressions. Images have the property of organ- izing themselves into general images, as they have the property of suggesting similar images. Thus 1 38 THE PSrCHOLOGT OF REASONING. we possess general ideas which are produced in us entirely by themselves, such as the general idea of a chair, a knife, etc. It will perhaps be thought that these views of cerebral physiology, although they may be hypo- thetical, have the advantage of according with the prepossession of many psychologists who seek the explanation of mental operations in the properties of the nervous system. Here we have the oppor- tunity of showing what this prevalent opinion is worth, it being more correct in appearance than in reality. Let us admit, for an instant, that it is not merely probable, but absolutely demonstrated that two similar states of consciousness have a single nerve element in the brain as their basis, and that this unity of seat explains the two effects of resemblance: suggestion and fusion. Does any one by chance believe that we have here, in the proper- ties of the nervous system, a true explanation of the properties of resemblance? That would be a singu- lar illusion. For this is no explanation whatever, but simply a transposition into physiological terms of the phenomenon which is claimed as explained. What is this single element which we state to be the basis of resemblance? How can we understand its unity if we have not the idea of number, of plurality, and is this idea not at least more complex than that of resemblance? ""Nous voila mi rouet,'' as Montaigne said. The truth is that we can only know exterior things by referring them to the laws of our mind, and that consequently the study of one of these THE MECHANISM OF REASONING. 129 objects, a brain for example, can give us no infor- mation as to the forms of our tJiought, for it always implies them. Those who maintain the contrary- are guilty of di. petit io principii,* II. Thus extended and modified, the law of resem- blance will enable us to understand the genesis of external perception. Let us study this genesis in itself, without any preconceived ideas, without considering that the phenomenon is a result of reasoning. True to our method, let us appeal to pathology, for morbid cases often let us perceive the secret of the normal state. Hypnagogic hallucinations afford a wide field of observations and experiments. M. Maury hit upon the clever idea of making experiments on his OAvn person, so as to estimate to what extent external impressions intervened in dreams. In the evening, when he began to fall asleep in his arm-chair, he asked a person placed by his side to produce sensa- tions in him without forewarning him, then to awaken him when he had already had time to dream a dream. The results obtained by this method really belong to the study of external perception, for what is a dream when produced under these conditions? It is a cerebral reaction following an impression of the senses — and this definition applies *The same observations may be advanced in the case of those authors who, like Hamilton, Brochard, James, Rabier, etc., try, without introducing Ehysiology, to explain the resemblance between two states of consciousness y the common elements in the two states, or by a partial identity of their elements. This pretended attempt at simplification simplifies nothing at all, for it replaces the idea of resemblance by the ideas of identity and of unity, which are merely its derivatives. We repeat that resemblance is a single, ultimate and irreducible idea. (Cf. Brochard, De la lot de si7?iilarite, Revue philosophique, March, 1880.) 130 THE PSrCHOLOGT OF REASONING. to perception. We shall presently see that the observer's dreams may be compared to artificial illusions of the senses. Here are the facts: His lips and the end of his nose are tickled with a feather; he dreams that he is undergoing a hor- rible torture, that a mask of wax is being placed on his face, then when it is being pulled off, the skin on his lips, nose and face is torn. A pair of tongs is rubbed with steel scissors a short distance from his ear; he dreams that he hears the sound of bells; this sound of bells soon becomes the tocsin; he thinks he is back in the days of June, 1848. He is made to breathe eau de cologne; he dreams that he is in a perfumer's shop, and the idea of perfume arouses that of the Orient; he is at Jean Farina's shop in Cairo. He is made to smell a burning match ; he dreams that he is at sea (the wind was then blowing on the windows) and that the Saint e-Barhe is pitching. He is pinched lightly on the neck ; he dreams that a blister is being placed there, which awakens the recollection of a doctor who attended him in his infancy. A warm iron is brought near to his face; he dreams of cJianffc2irs; the idea of these chauffeurs soon brings that of the Duchess d'Abrantes, whom he sup- poses in his dream to have taken him as her secre- tary. He had formerly read some details about cliaiiffeurs in the Memoirs of that clever woman, etc.* These experiments show that the qtiality of the sensory impression has an influence on the nature *Maury, So77i7neil et rives, p. 127. THE MECHANISM OF REASONING. 1 31 of the dream, for the trace of the generating im- pression is found again in the images of fantasy. But some other observations by the same author may be here given which are still more to the point; they concern dreams produced by subjective sensations. One night, M. Maury, when half awake, sees a luminous spark (a subjective sensation of the sight); he immediately transforms it, yield- ing already to the desire for sleep, into a lighted street lamp. Then before his eyes appears the Rue Hautefeuille, lit by night, as he had many a time seen it when he was living in it, thirty years before. The following is another example from the same author: "When I suffer from retinal congestion, coloured patches and luminous circles shape them- selves upon my eye-lid. Well, in the short instants during which imaginary images foretell the coming of sleep, I have often found that the luminous image which was due to the excitation of the optic nerve was in some way altered under the eyes of my imagination, and became transformed into a countenance whose bright features represented those of a more or less imaginary person. It was possible for me to follow the metamorphoses effected by my mind on this original nervous impression, for several seconds, and I again perceived upon the forehead and cheeks of these heads, red, blue or green colour, a luminous brightness which shone before my closed eyes, previous to the commencement of the hypnagogic hallucination."* In many similar cases it may be found that the *0p. cit., p. 59. 132 THE PSrCHOLOGT OF REASONING. imaginary image of the dream is preceded by phe- nomena of excitation, which are locahzed, perhaps wrongly, in the retina. The subject who is falling asleep begins by perceiving gleams, confused masses strewn with little coloured points, striae and filaments. The appearance of these amorphous sensations precedes the seeing of definite forms. M. Maury has expressed the idea that the dream hallucination arises from these "subjective spec- tres," and is derived from them by a kind of trans- formation. In this case there is, as M. Maury has correctly said, a met amor pilosis of images; and this metamorphosis recalls that of the zootrope. But in making this comparison we either say nothing at all, or we affirm a certain fact. We have seen how the change-effects produced by the zootrope are explained ; there is a series of impres- sions which follow each other at very short inter- vals; these impressions are not identical, no more are they absolutely different ; each resembles in part the one preceding and the one following it. By means of this partial identity each impression blends with its neighbour and forms with it a single whole. It is this fusion of successive impressions which gives the spectator the illusion of a single impression. We may suppose, in order to explain the genesis of the hypnagogic dream, that the principle of fusion operates not only between two sensations and between two images, but also between a sensation and an image. This supposition enables us to analyze the beginning of a hypnagogic hallucination in the fol- THE MECHANISM OF REASONING. 1 33 lowing manner. A luminous sensation, a spark for example, crosses the field of vision ; this sensa- tion recalls, by the effect of resemblance, the mental image of an object which also presents a luminous point, for example the image of a lighted street lamp. Let us denote the initial sensation by the letter A, and the complex image of a lighted street lamp by the letters ABCDEFGH, etc. ; the letter A in the second group represents the luminous point in the lamp — that is to say, the ele- ment which is common to the image of the lamp and the sensation of a spark. But, further, the two elements represented by A fuse together and form a single element in such a way that the image evoked blends with the sensation, and the spark is transformed into a street lamp ; then this last image recalls the entire image of the street by the associa- tion of contiguity. We find this same fusion of sensations with images in a large number of toxic hallucinations. One woman who had just taken some hashish in order to experience the blissful delirium which that substance produces in the Orientals, "saw her brother's portrait, which was above the piano, become animated and display a forked pig-tail, entirely black," etc. A moment afterward she went towards the door of a neighbouring room which was not lit. "Then," she says, "I experienced a frightful thing; I was choked and suffocated; I fell into an immense bottomless pit, the well at Bicetre. Like a drowning man who clutches for safety at a frail straw which he sees escaping him, so I tried 134 THE PSrCHOLOGT OF REASONING. to catch on to the stones which surrounded the pit; but they fell with me into that bottomless abyss." Her cries were heard, and she was brought back to the lighted part, and, her ideas changing with the new impressions, she thought she was at the opera ball, and she struck herself against a stool, which she took to be a masquerader, prone on the floor, and dancing in an unseemly fashion ; then she walked in the midst of a country of lanterns, which phantasmagoria was produced by the flame of the coals which burned in the fire- place.* When this sensory delirium is closely studied, its development may be readily followed. Its origin is in the sensations of every kind pro- duced by the external world in the midst of which the patient moves ; the impression of the senses calls up the images which resemble it ; these images appear, accumulate, become transformed under the influence of the toxic agent, become separated more and more from their point of origin, and finally create an entirely imaginary external world, which a new impulse of real sensations will again come to modify. But at the first moment of the evolution of the delirium, there is always at least a shade of resemblance between the exterior object and the images which it evokes, as is seen in the hallucina- tion of the well at Bicetre, produced by the dark room, and it is this resemblance which causes the fusion. Let us pass to the case of alcoholic delirium. We know that the visual hallucinations which *Moreau (de Tours), Du hachisch et de V alienation mentale, p. 14. THE MECHANISM OF REASONING. 135 accompany it consist of terrifying visions of little animals, cats, rats, insects, spiders, human heads separated from their trunk, etc. These hallucina- tions are not formed at once ; according to the evi- dence of the best observers, the visions are preceded by elementary troubles of a purely sensory charac- ter. The patient sees black points or luminous spots, which are animated with rapid movement ; these are the subjective sensations from which the hallucination is formed, and which the brain of the alcoholic inebriate ere long transforms, according as the delirium becomes more accentuated. "In some cases," says Magnan, "the patient at first sees a dark, blackish spot, with a vague outline, then with distinct boundaries with prolongations which be- come legs and head, so as to form an animal, a rat, a cat, or a man." Does this phenomenon not recall the zootropic metamorphoses in a striking fashion? Is it not quite naturally explained by a fusion of sensations and images? The same explanation may be readily adapted to all cases in which our brain causes the sensations which it receives to undergo a transformation. One of the most interesting examples of such transform.a- tions is afforded us by what might be called imagi- nary perceptions. Everybody must have noticed that when the environment is favourable one can at will picture to oneself the presence of a certain body, and perceive it as if it actually existed. We distin- guish a great many forms in clouds, in rocks, in the confused masses of dim or distant objects, in the flames of a fire, in the inequalities of a wall, or in 136 THE PSrCHOLOGT OF REASONING. the lines, holes and irregularities of a wooden table. It seems that Leonardo da Vinci recommended his pupils, when they were looking for a subject for a picture, to carefully study the appearance of sur- faces of wood ; in fact, at the end of a few minutes of attention, it does not take long to see certain animal forms, human heads, and sometimes whole scenes picturesquely arranged, shape themselves in the midst of the confused lines. On this matter I have a fairly extensive experience ; if I gaze attent- ively at a sheet of white paper, I always discover some figure on it; I can even copy it, and the drawings which I obtain by this process are gener- ally very superior to those which I am able to produce by imagination alone, although in reality they are not worth very much ; but this is a purely relative matter. I have often remarked that the figure is not formed right away, but slowly and by degrees, like a piece of decoration which is built up of successive pieces. The important thing is to obtain the first form ; if it is fairly vivid, it will not be long in completing itself, the edifice being noiselessly constructed on that first stone. It would be exceedingly interesting to study this imaginative side of our nature. The germ of a theory of invention, more genuine than all those which we have so far obtained, might perhaps indeed be found therein. However that may be, it is important for us to observe that the mind, in these perceptions, works on the fortuitous resem- blances which it discovers in an object ; it is through these points of resemblance that the imaginary THE MECHANISM OF REASONING. 137 image is evoked and becomes blended with the sen- sible impression. At the same time, which is a curious thing, the mind systematically neglects all the characteristics of the external object which do not harmonize with this fiction. Imaginary perceptions belong to the same family as illusions of the senses; they might be defined as voluntary illusions. They are the dramas of which we are at once author and spectator. Involuntary illusions supply us with similar facts. Every time that an illusion lends itself to analysis, it is perceived that the false exteriorized image, which, properly speaking, constitutes the illusion, in some way resembles that which gave it birth. For example, when, by reason of distance or ob- scurity, we take one person for another, or allow ourselves to be deceived by an imperfect resem- blance, we commit an error of identification ; in other words, the first image awakened by the exter- nal sensations resembles them and is blended with them. This, moreover, is confirmed by hypnotic experiments. Move your hand before the eyes of a somnambulist, imitating the movement of wings with your fingers; he immediately sees a bird and tries to catch it. Imitate a reptile's movement with your hand on the ground, and he sees a serpent. The general rule is that the subject sees all the ob- jects whose appearance is simulated. We pass by an insensible transition from the illusion, or false perception, to true perception. Let us see if every act of perception likewise takes its rise in an act of identification. 138 THE PSrCHOLOGT OF REASONING. I take hold of a book on a table; I lift it, open it, turn over its leaves, read it, and close it. All these acts have aroused a large number of impressions of touch, form, weight, temperature, resistance and movements in me, which are' united together and associated with the visual impressions which I .felt at the same time. Let us now suppose that I leave my room, and return to it after some minutes' absence. The book is still in the same place ; if I look at it, the visual impression which I experience awakens in my memory the images of sensations of. all kinds which I received when handling it a short time before. In short, images of touch, of the muscular and other senses proceed to combine with the visual sensation. Perception therefore takes place. But how does it L^ppen that this new visual sensation can awaken, under an ideal form, these impressions formerly received by the hand? There is in this case no bond of resemblance, nor even any bond of contiguity, for the actual sensation of sight is absolutely new, arid could not become asso- ciated with impressions received by the hand several minutes before. There is one reply, and only one, to this question ; it is that the actual aspect of the book resembles in part or in totality the former aspect, the recollection of which persists in my mind. From my preceding experience there sur- vives an ocular image of the book, associated with impressions from the hand. The appearance of the book as actually seen is fused with this visual recol- lection, which in its turn brings the train of tactile THE MECHANISM OF REASONING. 1 39 and muscular recollections to which it is bound into the field of consciousness. According to this interpretation, the series of states of consciousness which succeed each other in perception is as follows : The actual vision of the book (A) excites in our thought, by the force of similarity, the ocular image of the same book (B) which is due to a former vision, and this second state of consciousness in its turn excites, by the force of contiguity, the group of tactile and muscular impressions (C). It is the state of consciousness (B) which enables the first state to excite the third ; so I propose to call it the intermediate state of conseiousness, in order to express its function. The curious fact is that this image (B), the visual recollection of the uuok, does not make its appearance, in spite of the importance of the part it plays. When we look at the book, we do not have, simultaneously with this vision, the distinct recol- lection of a former vision. Yet this recollection constitutes an indispensable part of the operation, for without it perception would be impossible ; it is in a manner 'invisible and present;" it is fused with the visual sensation of the moment, and be- comes one with it,* so that this sensation is found directly associated with the group of tactile and muscular images. Let us represent the course of the phenomenon graphically. *We assume, for the sake of simplicity, that the actual vision of the book and the visual recollection of the same object completely resemble each other, and that the fusion is total; if the resemblance is only partial, the fusion also is partial. 140 THE PSrCHOLOGY OF REASONING. The perception of the book has the effect of uniting a visual sensation to a group of tactile and muscular images. The formation of this associa- tion constitutes the conclusion of the perceptive reasoning. This mental synthesis may be expressed by the formula A-C in which A represents the actual vision of the book, C the group of muscular and tactile images — that is to say, the fact inferred, and the sign — the bond of association which unites these two terms.* The psychological question which now arises is, as we have shown above, to explain the formation of this association. Now, we say that the actual vision of the object begins by reminding us of a former vision by means of the resemblance between these two states. This again m-ay be represented symbolically in the following manner: A:=B In this formula A continues to represent the actual vision of the book placed before our eyes, B represents the recollection of a former vision of that same book — that is to say, its visual image — and the sign = indicates the resemblance between the sensation and the image. This identification is, in *We employ algebraic signs merely in order to represent in a graphic manner the properties of the images which cooperate in an act of reasoning. It must be added that in no way do we place ourselves at the point of view of English logicians such as De Morgan, Boole, and Stanley Jevons, who also make use of these signs, but for the purpose of putting the problem of logic in the form of an equation, and of solving it by processes more or less analo- gous to those of algebra. Consult on this subject the interesting work of Louis Liard, Les logiciens anglais confemporains.) THE MECHANISM OF REASONING. 14I our opinion, the first part, the first act of external perception. In this case there is not only a recollection, a calling up of the image B, but this image, when once evoked, becomes fused with the sensation A, like the two sensations of the points of the com- passes in Weber's experiment. There is nothing astonishing in this result if we recollect that an image is almost a sensation. We have devoted a chapter to demonstrating that fact. We may there- fore indicate this fusion in the following manner, which has the advantage of appealing to the eye: [A=B] In this new formula the brackets express the fusion of the sensation and the image. Here the first act of perception finishes and the second begins. We have assumed in our example that former experiences had cemented an associa- tion between the vision of the book and the exceed- ingly diverse sensations which this object produces when we take it up, open it and read it, sensations the recollection of which has been designated by the letter C. This may be represented thus: B-C a formula in which B still represents the former vision of the book, C the experiences of active touch, and the sign — the pre-formed association between these two images. We therefore say that, through the fact of the fusion of A and B — that is to say, in consequence 142 THE PSrCHOLOGT OF liEASONING. of the fusion of the actual vision with the visual recollection of the object — C is associated directly with A, or, in other words, the idea of the invisible attributes of the object is directly associated in our mind with its visual aspect. Finally, we arrive at this last formula, which is self-explanatory : [A = B]-C To sum up, the whole operation may be analyzed thus: An association by resemblance, the purpose of which is to introduce an association by contiguity. As the latter is the end, it diverts the attention from the former, which is the means. It would be easy to simplify the description of this operation by showing that it may be reduced to the partial assimilation of two images. In fact, perception is produced by the partial fusion of the ocular sensation which the object actually produces upon us with the complete recollection of the same object, or of a similar object, which lives in our memory. This assimilation of two impressions is the biological property from which reasoning springs. We began by offering this mechanism of percep- tion as a hypothesis. But if this explanation be compared with all the pathological facts which have been cited, it will be recognized that the hypothesis very nearly attains to the rank of theory. We have seen that in all the morbid perceptions which lend themselves to analysis, the phenomenon begins with an act of identification — that is to say, by z. fusion of the excitative sensation with the first image wJiicJi THE MECHANISM OF REASONING. 143 it evokes. We may recall, among the most typical cases, the sleeper who, seeing a spark, transforms it into a lighted street-lamp, and sees a street lit at night appearing before him ; the alcoholic inebriate who, seeing black points moving in his field of vision, transforms them into little black beasts with lengthening legs; the wide-awake person who, by fixing his attention on the confused lines on a table, finishes by seeing fixed forms come out of them ; and, finally, the individual affected by an illusion of the senses, who confounds a stranger with a friend, letting himself be deceived by a rough resemblance of size, of figure, or of dress. Always and every- where external perception, whether it be exact, whether it be false (illusion), or whether it be insane (hallucination), takes its rise in a fusion between the sensations of the external world and the images which these sensations cause to spring up in the mind. The only difference is that in false and patholog- ical perceptions a shade of resemblance is sufficient to produce suggestion, while in correct perception we only take account of an ensemble of resem- blances, and even a shade of difference is enough to prevent suggestion. Helmholtz has remarked that in the stereoscopic arrangement the presence of a badly-projected shadow destroys the illusion. But we are obliged, in the interests of clearness, to put aside these details. All that we retain of the pre- ceding discussion is the fact that perception takes its rise in identification. Moreover, how could it be otherwise? When 144 THE PSrCHOLOGT OF REASONING. we perceive an external object, we receive sensa- tions which are always new and distinct from all those which have preceded them. How then could those new sensations evoke past, former states, such as images, if not by the effect of resemblance? Resemblance is the only bond which could unite states separated by time. Let us state this problem in an a priori form, employing the formulae which we have already made use of. On the one hand, B is associated with C. On the other hand, A resem- bles B. How can A become associated with C, if not through the medium of B? Before going further, we wish to show that these complex phenomena in which similarity and con- tiguity are combined have already been noticed by psychologists, although they did not understand their significance. Two passages may be read in this connection, one from James Mill {A?ialysis of the Phenomena of the Hiunan Mind, Vol. I, p. in, et seg.), and the other from Mr. Bain (eod. loc, p. 464, et seg.). We shall quote only Mr. Sully, who remarks, in his book, entitled Ontlines of Psy- chology, that the two laws of . contiguity and simil- arity are at once distinct and inseparable. "Each mode of reproduction may be said to involve the cooperation, in different proportions, or with differ- ent degrees of distinctness, of two elements, a link of similarity or identity and a link of contiguity. Thus when a person's name calls up the image of his face, it is because the present sound is automat- ically identified with previously heard sounds. So, too, revival by similarity commonly involves con- THE MECHANISM OF REASONING. 1 45 tiguity as shown above. But in ordinary cases what we call revival by similarity involves the call- ing up of concomitant circumstances." The author symbolizes the relation between the two laws as fol- lows: A A Contiguity Similarity (a) — 71 c — (a) — f . In the first case the process of identification be- tween A and (a) is automatic or unconscious, and the revived concomitants {jt) are thought of as quite distinct from that which revives them ; whereas in the second case the identification is the important step in the process, and the concomitants (c and f) are not distinctly separated from the identified element (a). We have only to compare this plan with our own to recognize the identity of the two : First of all we see therein the fusion of one state of consciousness with a second similar state, then the suggestion of a third state which was associated with the second by contiguity. But what is yet more important to notice is that the process of perception which we have described is, according to Stuart Mill, Mr. Bain and Mr. Sully, a general process, which is realized every time that an association of ideas comes into play — that is to say, at every instant in our lives. Now, as we shall presently proceed to demonstrate the logical value of this process, which constitutes true reasoning, we shall consider reasoning, not as an accidental fact, but as the constant element in our 146 THE PSrCHOLOGT OF REASONING. lives, the fabric of all our thoughts. Thus, we shall come to accept as a demonstrated truth that appar- ent paradox of Wundt's : The mind might be defined as a tiling which reasons. III. The phenomena which we are at present study- ing are so important that we are willing to protract the examination. Perception, we have said, is an operation in three terms; we have seen how many proofs lend support to this proposition. But we wish to continue the demonstration to its conclusion by quoting examples of perceptions in which the distinct existence of these three terms may be directly recognized by inspection alone. This occurs whenever perception, in evolving and becom- ing complicated, tends to become confused with conscious and voluntary reasonings. Let us take a simple example, which we shall afterwards try to complicate. In what does the process of reading a written word consist? At first sight it is merely bringing an association of con- tiguity between a graphic sign and an idea into operation. When the graphic sign is very clear, like a printed letter, the suggestion of the image follows the seeing of the sign immediately; the operation appears to be in two terms, like the ma- jority of our ordinary perceptions. For example, the image of a house appears vaguely when we read the word ' ' house. ' ' But let us complicate the opera- tion a little ; let us try to retard it in order to grasp it better in detail, and a supplementary term is im- THE MECHANISM OF REASONING. 147 mediately detached. We take, in place of a printed word, a word written by the hand and almost illegible. Then we perceive that the sight of the characters is not enough to make them understood; it is necessary, in addition, to recognize them, to state that this disfigured letter is an «, this other a c, and so on. But how is this recognition possible, if not by a comparison between the altered character and the recollection of the normal character? We decide that this letter is an a by ascertaining that it more or less resembles the letter a which we know. Eliminate this recollection, this intermediate state of consciousness, and the operation becomes impos- sible. There are numerous examples of the same kind. One more may be given. There are some diag- noses which are made at a distance, so far as they are easy ; a neuro-pathologist has often merely to see a sufferer from ataxia walking, or a paralytic (Park- inson's disease) moving in the street in order to recognize their disease. The mere sight of a prom- inent symptom evokes the name of the disease, and the representation of all the other symptoms which belong to the same affection. But most frequently the sight and even the methodical examination of the patients is not enough; the physician must gather his recollections together in order to make the diagnosis. What does he do then? He com- pares the case he has before him with analogous cases which have already occurred. Trousseau even said that in this work of comparison he dis- tinctly remembered patients whom he had formerly 148 THE PSrCHOLOGT OF REASONING. seen in the hospital while he was a student; he pictured their appearance, and even, he says, the number of their bed. This conscious reversion to previous and similar cases brings the intermediate state of consciousness prominently into view. This state is always apparent when the similarity does not operate in a sure and infallible manner. We may therefore affirm that three images suc- ceed each other in the perception of an external object. We have still to show the importance of this analysis. It is exact, it may be said, but what is the use of it? It describes for describing's sake; it supplies no information as to the mechanism of reasoning; after having engaged in a minute psy- chological dissection, we know no more of the mat- ter than we did before. Our aim is to show briefly, and above all as clearly as possible, the significance of the results obtained. We are convinced that we are now able to give an exact theory of the mechanism of reason- ing; in fact, thanks to this supposition that in every perception there exists an intennediate state of con- sciousness (B), serving as the connecting link be- tween the impression of the senses (A) and the inferred images (C), everything becomes clear; this supposition is like the word which, interpolated in a mutilated text, reveals its meaning. We shall presently see that we can recognize, in the account of perception reconstituted in this manner, all the parts which go to form a regular act of reasoning. First of all, the act of perception becomes a transition from the known to the unknown by THE MECHANISM OF REASONING. 149 means of a resemblance, and it will be remembered that this is a rough, though exact, definition of reasoning. The known fact is the sensation which we actually experience, for example, the visual sensation of a book placed on a table. The un- known fact is the nature of the object which gives us this visual sensation. We obtain this desired idea through the suggestion of a recollection — the image of a book ; now, the transition from the sen- sation to the image, from the known fact to the unknown fact, is afforded us by the resemblance of the visual object to the object with which we identify it. It will perhaps be said that reasoning is some- thing more than this consecution of images ; it is a judgment, it is the formation of a new belief. Therefore it is not sufTficient to explain how the complete and detailed image of the book can be called forth on account of an elementary sensation of sight or of touch ; it would still be necessary to give an account of this new belief which enables us to affirm that "this is a book." The suggestion of a fact is one thing, and the judgment which accepts it as true is another. For example, we shall not explain the reasoning v/hich makes us say that Paul is mortal, if we merely show how the idea of the death of this individual comes to our mind; as we may yet state how this idea determines our convic- tion. Such is the objection which certain readers will not fail to offer. Let us try to reply to it. Belief, conviction and assent are among those vague, liquescent and ill-defined phenomena which are 150 THE PSYCHOLOG7' OF REASONING. numerous in psychology; they could with difficulty be made the subject of methodical study. But psychologists have adopted a bias; they have remarked that belief generally resulted from a rela- tion between images. When two facts have often occurred at the same time or in immediate succes- sion, the corresponding images have a tendency to become connected in our mind, and, further, we have a tendency to believe that the phenomena, the ideas of which are associated in our mind, are likewise associated in reality. (See p. 79.) This stated, it is clear that a theory will explain the formation of a new belief if it explains not only the suggestion of the idea to be affirmed, but the asso- ciation, the organization of this idea with others. Let us repeat our argument, so as to make it clearer. We admit that it is not sufficient to say, in order to explain our reasoned conviction that a certain man must die, how we obtain the idea of the death of a man ; but the moment we explain how this idea of death becomes associated with that of the individual in question, so as to produce the belief that he is mortal, we have attained our end, and demonstrated that which required demonstration. Well, has this demonstration been furnished? Has the preceding analysis explained how, apart from all experience, merely by an operation of mental laws, an association can be formed between two images? This was, it will be remembered, one of the conditions which we had urged (p. 94) against every explanation of reasoning — this condi- tion seems to us to be fulfilled. We have seen the THE MECHANISM OF REASONING. 15 1 reason why the detailed image of the book is com- bined with the visual sensation of the moment ; it is because these two impressions have points of resem- blance which weld them together. Thus are ex- plained all the syntheses of our sensations and of our recollections. But that is not all ; a reasoned conclusion does not merely include an adoption of a new truth. This truth also presents that particular character of being a logical consequence of a truth already admitted. In psychological terms the association of images which is established by reasoning takes place through the medium of preexisting associa- tions which are called premisses. To reason is to establish associations on the model of other associ- ations which are already formed. (See p. 95.) It remains to show that our thesis on the mechanism of perception gives an account of this latter charac- ter of reasoning. To this end, we must establish a new parallel between external perception and the syllogism. . In the first place, it will be observed that per- ception is an operation in three terms, A, B, C. The first term (A) represents the actual vision of the object, the second (B) its former vision, and the third (C) the inferred properties. The syllogism is also an operation in three terms; in the example which we analyzed before, these terms are Socrates, man and mortal. Again, in the syllogism the mean term enters into the major and the minor and disappears in the conclusion, although it is preparatory to it. It is 152 THE PSrCIIOLOGT OF REASONING. the term "man." Reasoning, as Boole remarks, is the elimination of a mean term in a system of three terms. This mean term, we say, is prepara- tory to the conclusion ; for if Socrates were not a man, he would not be mortal. Similarly in percep- tion, the term B, the visual recollection of the object, is a true mean term ; on the one hand, it vanishes when we reach the conclusion, for it blends with the actual vision (A) ; on the other hand, it is preparatory to the conclusion, for if the actual aspect of the object did not resemble the former aspect already seen (B), we would not be able to recog- nize it. But the parallel may be pushed much further. It is possible to divide the act of perception into three slices, as is done with the syllogism — that is to say, into three parts which correspond to the three verbal propositions of an act of logical reason- ing. Let us begin by translating the familiar syllo- gism, which we have used so often, into psychological language. Let us take the major premiss first: A II men are mortal . This proposition states, according to a logician's analysis,* that the attributes connoted by "man" never exist unless conjoined with the attribute called mortality, so that wherever the first attribute is found we may be sure of the existence of the second. It is a relation between two facts. Psy- chologically, the proposition has another meaning; it means that there exists in our mind an associa- *John Stuart Mill, Logic, p. 122. THE MECHANISM OF REASONING. 153 tion between two groups of images, one group of abstract images representing man, and one group of generic images representing death. We understand by the word association that these two images are produced simultaneously or in immediate succession in our mind. We say again that the two images are contiguous. Consequently we shall call our major proposition a proposition of contiguity. It is to our past experience, or to the testimony of others, that we owe that association ; it is given, acquired, considered as corect, at the moment when we perform the act of reasoning. It is upon it that our conclusion will depend. The minor premiss of the reasoning Socrates is a man, is of another nature. It signifies from the logical point of view that there is a perfect resem- blance, an identity, between certain attributes of Socrates (colour, form, size, internal structure) and the attributes of humanity. That is what the proposition signifies; now, as a distinct question, what is it from the psychological point of view? It is an act of assimilation between the image of cer- tain attributes of Socrates and the generic image of humanity. Here the mind seizes a resemblance between two groups of images, and the proposition which expresses this internal act may be called a proposition of resemblance. The conclusion Socrates is mortal, contains the truth discovered by deduction. Con- sidered from the objective point of view, it signifies 154 ^^HE PSYCHOLOGl' OF REASONING. that there exists a relation of coexistence between the individual called Socrates and the attributes of mortality, or, in other words, that Socrates pos- sesses these attributes. Psychologically, this prop- osition indicates that a relation of contiguity has been established in our mind between the image of Socrates and the image of mortality. To sum up, the preceding reasoning may be divided into three propositions: (i) A proposition of coexistence, the major premiss; (2) a proposition of resemblance, the minor premiss ; (3) a proposi- tion of coexistence, the conclusion.* Now, let us put the propositions of the syllogism, on the one hand, opposite the symbolic formulae which we employed in our analysis of perception, on the other hand : Major premiss: All ineji are mortal B— C Minor premiss: Socrates is a man A=B Conclusion: Socrates is mortal (A=B) — C The major premiss of our syllogism is, we have said, a proposition of coexistence; it signifies that the generic image of man is associated in our mind with the abstract image of iriortality. Similarly, in the formula B — C we find an association of images indicated ; for this formula means that the former *Arrnrdinff to Mill {of. cit., p. 123;, the principle involved in every inference strikfng?y resembles the"^ axioms of mathematics. It is that •^things whixhcolxlst with the same thing, coex st with one another.' Thus: Sorratps coexists with man-Mortality coexists with man.-Therefore Socra el and mortal ty coexist with one another. But there is an error in tl?fs analysis- ?n reality the reasoning is not composed of three propositions o coeKistei ce The minor premiss is a proposition of resemblance. To say that Socrates is a man mea£s that he resembles men whom we know. Mill him..plfremarks this (p ^Ss). So we ought rather to say:-Socrates resembles mi^L-imn coexists wi^th^^ coexists w th mortality. If 1 were dTsl^ed tha? a p inciple should be deduced from tn.s operation at all rnsts we would propose the following: "A thing which resembes anothe. thing coinmunicates to it the property which it has of coexisting with a third." THE MECHANISM OF REASONING. 155 vision of the book (B) is associated with the image of its tangible quahties (C). Therefore, on both sides there is the same association of contiguity. The minor premiss of our syllogism expresses a resemblance between the mental representation of Socrates and that of the attributes connoted by the word humanity. In the formula A = B, there is also an identification between the actual vision of the book (A) and the recollection of a former vision (B) — that is to say, between the sensation and the image of one and the samie thing. Therefore, on both sides there is the same association of resem- blance. Finally, the conclusion of our syllogism indicates that an association of contiguity exists between the image of Socrates and the image of death. In the formula (A=B) — C, we also see an association of contiguity become formed between the vision of the book and the idea of its tangible attributes. There- fore, there is, once more on both sides, the same association of contiguity. It would be superfluous to dwell further on this matter. Perception is evidently composed of the same parts as formal reasoning. But the direct study of form.al reasoning cannot lead to a theory of that operation, for the states of consciousness which are its subject are too complicated for one to be able to observe the law according to which they are connected. When I say, "All men are mortal; Socrates is a man, therefore he is mortal," what takes place in my mind? Of that I know nothing accurately. I seem to perceive a train of confused 156 THE PSTCHOLOGT OF REASONING. images. In any case I am unable to understand how these images are connected and disposed in reasoning. I am, to employ one of Wundt's comparisons, like a physicist who wished to study the vibrations of a pendulum by looking at them through a keyhole, or like an astronomer who, to study the sky, took up his residence in a cellar. The study of simple perceptions reveals to us the law we seek ; it shows us that sensations and images become organized by virtue of the two laws of sim- ilarity and of contiguity. The study of morbid cases, dreams, hallucinations, etc., throws full light upon the subject. Finally, our theory satisfies the three conditions which we had laid down ; it introduces only the known laws of the association of images ; it explains how an association is established between two images by the operation of mental laws alone; finally, it explains how that association is formed on the model of former associations. All the preceding discussion may be reduced to a single formula, which will serve us as a defini- tion: Reasoning is the establisJiment of an association between two states of cofiscionsness, by means of an intermediate state of consciousness which resembles the first state, which is associated with the second, and which, by fusing itself with the first, associates it with the second. It is often convenient to characterize a theory in a word. Our theory of reasoning is a theory of substitution. We see in it the main term (A) sub- THE MECHANISM OF REASONING. 157 stituting itself for the middle term (B) — that is to say, one image taking the place of another and partially identical image.* *We have had the pleasure of meeting a very analogous theory in an article signed by a very keen and original psychologist, Mr. William James. After having defined similarity as tiie association of wholes, or aggregates by virtue of their common points, he observes that the process of association by similarity closely resembles that of reasoning properly so called. Reason- ing, says he again, consists in a substitution of parts of different wholes. In a certam sense it would be not at all too paradoxical to say that confusion and reasoning are two species of the same genus. We identify the thing in question with a part of a certain other whole. In this common process, if the operation be exact, there is reasoning; if not there is confusion. — We quote from M. Renouvier's analysis. {Critique philosophiqtie, 1879, p.S7o et seq.) CHAPTER V. CONCLUSION. We consider it useful to distinguish carefully between the results of our analysis and the conclu- sions which we shall presently draw therefrom. We believe it will be readily admitted that in every perception there exists a succession of three images, the first of which fuses with the second, which in its turn suggests the third. The existence of these three images and their coordination appears to be now and heretofore well established. These are facts which psychologists of any school may admit without fear of compromising the theories that are dear to them. But the conclusions, the interpretations which these facts suggest, will not, in all probability, meet with so ready an assent, for I shall presently have to touch upon questions on which many minds are already decided. It is only right to add that these interpretations are much less solidly established than their point of departure. Under cover of these reservations I shall try to show that the theory of tJirec images is applicable to reasonings of every kind, and therefore consti- tutes a general theory of reasoning. We might already afifirm, a priori, the legitimacy of this I c8 CONCLUSION. 159 investigation ; for unless it be maintained that higher reasoning has been created in its entirety, it must certainly be admitted that it is the termina- tion of an ascending evolution, and we must indicate from what lower form it proceeds. The reader already knows that there is no de- cided difference between perception and logical reasoning; the two operations are both reasonings, transitions from the known to the unknown. The analogy is so close that we were able to compare perception with formal reasoning, and to show that perception contains all the essential elements of a peripatetic syllogism. (See p. 88.) In short, per- ception and logical reasoning are only the two extremes of a long series of phenomena, and when we place ourselves in the middle of the series we find inferences which belong to both at the same time. (See p. 70.) Further, we have shown that a kind of filial relationship exists between perception and the reasonings of conscious logic. Thus, when we make systematized anaesthesia, which has been developed in a patient relatively to a certain person, gradually disappear, the thing which appears first of all is the perception of the person as species ; and it is only afterwards, by a kind of ascending evolu- tion, that the recognition of the person as individ- ual takes place ; now, we know that recognition is a complex operation Avhich touches closely upon reasoning properly so called. All these reasons lead to the belief that perceptive reasoning and logical reasoning imply the same mechanism, (See P- 77-) l6o THE PSrCHOLOGT OF REASONING. Let us now examine the principal objections which may be made to this argument. One of the characteristics which distinguish logical reasoning from perception is that objects constitute the material of logical reasoning and sensations the material of perceptive reasoning. There follows from this a second difference, drawn from the existence of language ; language being formed in order to name objects and not sensations, lends its support to logical reasoning and refuses it to perception. But let us neglect this second difference, which is secondary and derivative, so as to devote our attention to the first. Let us be exact. In what, from the psychical point of view, do the terms of logical reasonings consist? Some consist of general and abstract ideas; the others are recollections of facts, or recollections of particular objects. All of them are the residues of former perceptions; they proceed from them more or less directly, but they all do proceed from them; they are all percepts. Up to the present we have considered the percept as a synthesis of sensations and images, or rather as a sort of microcosm; here the percept becomes unity. We may compare it to a chemical radicle, which, although composed of atoms of different bodies, reacts like a simple body. The percept of a person or of a fact, in which we saw the result of automatic reasoning, becomes a term in complicated reasonings ; so that we might say of these latter operations that therein we reason on reasonings. This stated, the question is to know whether CONCLUSION. l6l logical reasoning is constructed with percepts as the percept is constructed with sensations. No good reason can be alleged against this unity of mental composition ; we do not see why percepts, which are groups of images, should have other properties than isolated images and sensations ; and we do not see why the percepts of logical reasoning should not associate themselves according to the same processes as the images and sensations in automatic reasoning. To make ourselves better understood, let us appeal to an analogy. When we wish to prove that a visual recollection produces the same chro- matic effects as the actual vision, we experiment with the most simple visual recollection, the repre- sentation of a colour; we have seen elsewhere (p. 40) that the idea of that colour, of red, for example, produces a consecutive green image. The experiment only succeeds by placing one's self under such conditions of simplicity; no consecutive coloured sensation would be obtained by mentally representing to one's self a com- plicated object, such as a country landscape or the appearance of a market. Nevertheless, we cer- tainly do not hesitate to transfer to the complex image the phenomenon observed in the simple image of a colour, and to make this phenomenon a general property of images. We believe that the generalization is quite as legitimate in the case of reasoning; we claim that in this case again, what can scarcely be ascertained directly save for isolated images should be transferred to complex images; 1 63 THE PSYCHOLOGT OF REASONING. we claim that it should be admitted that the terms of logical reasoning are connected in accordance with the same laws as the images of perceptive reasoning, because these terms are groups of images which should have the same properties as isolated images. But there is a still more decisive reason for be- lieving that logical reasoning is constructed on the same model as perception. Our analysis of percep- tion took the study of the syllogism as its point of departure; it was proposed as an aim to find in perception again all the parts of which formal rea- soning is composed; this method led us to discover three terms and three propositions in perception, comparable in all respects to the terms and the propositions of the syllogism. From that dissection resulted the theory of three images. Why should this theory not be applicable with entire justice to the syllogism, since it comes from it? We shall conclude with some reflections on the order in which the syllogistic propositions are arranged. Mr. Spencer has directed a certain number of critcisms against the syllogism in this connection, some of which appear to us to be well founded. "When I say," he says,'^ ''All crystals have planes of cleavage; ' ' T/ns is a crystal; ''Therefore, this lias a plane of cleavage; and when it is asserted that this describes the mental process by which I reached the conclusion, *0/. at.. Vol. II. p. 97- CONCLUSION. 163 there arises the question, What induced me to think of 'all crystals'? Did the concept 'all crystals' come into my mind by a happy accident the moment before I was about to draw an infer- ence respecting a particular crystal? No one will assert such an absurdity. It must have been, then, that a consciousness of the particular crystal identi- fied by me as such was antecedent to my concep- tion of 'all crystals.' " That is, one of the elements of the minor premiss has suggested one of the general elements of the major premiss. This objection seems to us very reasonable, as it leads us to transpose the premisses in the following way: This is a crystal; All crystals have planes of cleavage; This has a plane of cleavage. But we are quite unable to follow Mr. Spencer in his objections to this new arrangement of the premisses. Why, he asks, have I been led by the idea of this particular crystal to think of all crys- tals, and not of quite another class? Why? we may answer. It is in consequence of a relation of resemblance; it is because "this" resembles a crys- tal, crystals which we know, and consequently the class of crystals. Why, says Mr. Spencer again, when I think of crystals do I think of their planes of cleavage, and not of their angles, their axes, or of any other of their properties? I think of their planes of cleavage by reason of a pre-established relation of coexistence between crystals and planes of cleavage. I would have been able to think of any other attribute, it is true ; in that case the 164 THE PSrCHOLOGT OF REASONING. conclusion would have been different, and instead of saying that this crystal has a plane of cleavage, I would have attributed to it a certain other property. That is all. Is a thing impossible because it would have been possible otherwise? It is therefore necessary in every syllogism to transpose the premisses, to place the minor before the major, and to say: "This is a crystal; all crys- tals have planes of cleavage, this has a plane of cleavage;" or again, "Socrates is a man; all men are mortal, therefore Socrates is mortal." We then discover a striking resemblance be- tween perceptive reasoning and logical reasoning. In the two cases, the operation begins in an asso- ciation of resemblance. The new arrangement of the syllogistic propositions is therefore quite con- formable to the course which the mind follows in reasoning, since it reproduces the course of percep- tive reasoning, that which constitutes the true "liv- ing" reasoning, while the reasonings of logical treatises are dead reasonings, dissected by the logicians.* *Thus we believe that, in all kinds of reasoning, the psychical labour consists essentially of a fusion of images. But this conclusion in no way prevents us from recognising that the human mind passed over an immense interval on the day when it passed from perceptive and unconscious reason- ing, which is common to the majority of animals, to logical, conscious, really scientific reasonings, which are only accessible to a very small number of individuals. The superiority of these latter reasonings depends upon an infinity of causes; they imply the power of seizing, beneath apparent con- trasts, real similitudes (for example, the assimilation of the mechanical force of the wind with that of a waterfall, of the flower with a transformed leaf, of the skull with a vertebra, of the lightning with the electric spark, of respira- tion with combustion, etc.); they imply a comparison between the various parts of reasoning, which are all brought before the mind, and which permit it to judge if the conclusion is justified by its premisses; finally, they have the result not only of demonstrating, but of explaining, by bringing the inferred fact back under a more general law; in this lies the superiority of reasoning over observation, of the deductive sciences over the experimental sciences, of the geometry of Euclid over tachimetry. CONCLUSION. 165 II. Let us admit that reasoning is essentially one, that the simplest of inferences is, like the highest of generalizations, produced by a fusion and a grouping of images. From this general definition of reasoning we may deduce its utility, its function, its sphere and its limits. If it be recollected that images are fragments, residues of former sensa- tions; that they spring from the same place as for- mer sensations have been received, in the sensory centres of the cerebral surface layers; it will be understood that the purpose of these images, in grouping themselves in reasonings, according to the laws of their affinity, is to replace the absent sensa- tions. Such is therefore the function of reasoning; it enlarges the sphere of our sensibility, and extends it to all objects which our senses cannot know directly. Thus understood, reasoning is a supple- mentary sense, which has the advantage of being freed from those strict conditions of time and space, the two enemies of human knowledge. Reasoning is in turn the eye which sees, the hand which touches and the ear which hears. We find examples of these different functions in the study of perceptions. When, during the night, we cross a room which we know, the impressions of touch which we feel excite visual images which guide us among the furniture and prevent our striking ourselves and stumbling. The mechanism of this suggestion is a 1 66 THE PSrCHOLOGT OF REASONING. perception of touch — that is to say, a reasoning. Reasoning therefore enables us in a manner to see, by means of the visual image, the object which we touch in the darkness. And this internal vision is exceptionally developed in somnambulists, who usually walk with their eyes closed and can avoid obstacles of every kind by their hyperaesthetic sense of touch. It is probable that if the somnambulist does not see by his eyes, he sees by reasoning. It is reasoning which, from the depths of the darkness, guides him by means of an internal light, formed by visual images. Thus we understand a multi- tude of improbable feats, how, for example, a cer- tain somnambulist can write a page of manuscript, read it over and correct it exactly, without the cooperation of sight. We are all acquainted with the thoroughly authentic story of an abbe who wrote sermons dur- ing his fits of natural somnambulism.* One day a white sheet was placed on the page of manuscript which he had just finished, and he re-read it on this white sheet, making erasures and corrections here and there which coincided exactly with the text below. In this case he had a most exact visual image of the written page, and he exteriorized that image on the sheet of paper, thus replacing sight by reasoning. These extreme cases give us the key to the normal state. It is more difificult to demonstrate directly that logical reasoning is like a supplementary sense, and *This observation is cited by Bersot, Mesmer et le magnetisttie animal, 5th edition, p. 247. CONCL US /ON. 1 67 that its purpose is to give us an internal vision* which protracts the external vision. In the syllo- gism the fact affirmed by the conclusion is too com- plex, too abstract, for the knowledge of it to appear comparable to a sensation. However, many authors have maintained an analogous thesis ; Schopenhauer said that the axioms of geometry are felt. We shall no longer have any doubt on this point, if we carefully observe what happens with hysterical subjects, those species of voyantcs who very often materialize the conclusions of their reasonings and make hallucinations out of them. One day we suggest to W , who is in the state of somnambulism, that she should make a ges- ture of contempt at a bust of Gall placed on a neighbouring table. f When she awakes she makes the gesture indicated, and seeking to explain the motive of this suggested act, which is for her spon- taneous and free, she says: "That bust is disgust- ing." This is a reasoned conclusion; but note that this conclusion takes the form of a hallucination; the patient sees the bust under a disgusting aspect, M. Fere has related this second example to me: We give, one day, to another patient the hallucina- tion of M. Fere, and we make her believe that she is fighting him ; during this imaginary combat the patient strikes his temple a vigorous blow with her fist, which stretches him on the ground. On the morrow the awakened patient sees M. Fere enter- *Here we take, for the sake of greater clearness, vision in place of all the senses, that is to say the species for the genus. tThe majority of the facts which we describe have been elucidated by us in the course of researches pursued in common with Dr. Fere at the Sal- petriere hospital. l6S THE PSrCIlOLOGl' OF REASONING. ing the ward, and she perceives that he carries a black-and-blue mark on his temple. This mark was produced by the imaginary blow which she had given him on the previous evening. Here again the conclusion of the reasoning culminates in vision. The patient performed the following unconscious reasoning: I have given him an extremely violent blow with my fist on his temple; therefore he must carry the mark of it. Hence the hallucination of an ecchymosis. Upon coming out of a phase of profound lethargy which has lasted five minutes at the most, a patient imagines that she has slept for several hours. We answer that it is two o'clock in the afternoon (it was really nine o'clock in the morning). The patient immediately feels the most acute hunger, and begs us to let her go and dine. Here again there is reasoning (it is late, therefore I am hungry) which produces as its conclusion a kind of organic hallucination, the hallucination of hunger. The preceding examples are unpublished ; the following are some others which have already been published, but the phenomenon has not yet been studied from the point of view at which we place ourselves. M. Richet suggests to Miss C- — ■ — , when she is in a trance, that she is going on board a packet boat, and that she is leaving for New York; soon the rolling of the boat makes itself felt, the woman becomes pale, and, throwing her head back, she has an attack of real nausea. This hallucina- tion is produced by the logical development which the subject causes the suggestion of a sea voyage to undergo ; this sickness is a conclusion from un- CONCLUSION. 169 conscious reasoning: I am on a packet-boat, there- fore it rolls, therefore I am sick. M. Richet sug- gests to one of his friends that he is making a balloon ascent; the subject soon sees a huge shining ball in the distance ; it is the earth, a sight which he suggests to himself, and which is again a deduc- tion from the original suggestion. When he pre- pares to descend, M. Richet suggests that a piece of string is suspended down to the earth and that the subject should allow himself to slide down, holding on to the string with his hand. During this dangerous excursion the subject stopped suddenly, saying that the rope burned his hands. This is a fresh deduction which takes the hallucinatory form. The authors who comment upon facts of this kind see in them merely a manifestation of the association of ideas. It would be, they say, by association of ideas that the patient who believes herself to be on a steamer experiences nausea, etc. When they have pronounced that great word "asso- ciation," they think they have said everything. That is a mistake. Although there are hallucina- tions which are scarcely anything but recollections resuscitated under a sensible form, and in which the mind of the patient lets itself be guided by pre- established and completely formed associations, this is not a general rule. In other hallucinations it is quite the contrary ; the patient imagines, creates, invents an entire sensation, an object, an event, a scene or a picture, which is as new for him as for us, the witnesses. Far from confining himself to associations already formed, he makes 170 THE PSrCHOLOGT OF REASONING. new ones, like that hallucinated subject who, rising in a balloon, sees the earth at his feet, although up to that day he had never made an aerostatic ascent. Now, this establishing of new associations, this construction of images according to a new plan, is really reasoning. But it is clear that between rea- soning and recollection there are all possible transi- tions, for reasoning is an application of a recollection to a datum which is new but similar; and that which predominates in the operation is the repro- duction of the recollection, or its new application, as the case may be. Here are some other facts which call for the same reflections. One of our patients, transformed by suggestion into a priest, sees himself, upon awaken- ing, dressed in a cassock which smells badly. A patient of M. Richet's, transformed into the Arch- bishop of Paris, spontaneously sees the President of the Republic, presents his New Year compliments to him, and hears the President replying in a low voice, ^'' eaii b^nite de cour.'" Another, transformed into a general, sees horses and aides-de-camp sur- rounding him, gives orders, reprimands, uses the telescope, etc. The curious thing is that when the subject is intelligent and imaginative, the sugges- tion which is directed towards him produces, not an isolated hallucination, but numerous hallucinations which form a picture. I may refer, in this connec- tion, to the examples mentioned by M. Paul Richer (hallucinations of a dinner in the country, of a fete, of an open-air ball, etc.)* In these examples we *0^. cii., passim. CONCLUSION. 171 often seize, on the wing, the logical exercise of the mind which draws every possible deduction from the theme imposed upon it. Nothing is better suited to show that the purpose of reasoning is to create a kind of logical vision, so much the more striking as under these circumstances, logical — or in other words, hallucinatory — vision surpasses actual vision in intensity. The same phenomenon is frequently met with in mental alienation, when the insane person draws from a delirious conception a conclusion which assumes the hallucinatory form. Everybody knows the story of the man who, believing himself to be a king, took his rags for a royal mantle. A less- known case is that of a poor woman who, having one evening received, in a hallucination, a visit from her husband, had thereafter the hallucination of pregnancy. In this example one of the two hallucinations forms the premiss, and the second is the conclusion, and each conclusion becomes a hal- lucination. In our opinion, the hypnotic experiments which we have just described give a most beautiful demonstration of a phenomenon which is doubtful and almost altogether elusive in the normal state. We are inclined to believe that ordinary reason- ings culminate in a similar but less intense vision. We throw a stone into a pond. The stone, after having produced noisy splashes on the surface of the water, falls to the bottom, while around the point where it fell there forms a series of waves. Thence we infer by reasoning that another stone 172 THE rSrCHOLOGT OF REASONING. thrown into the same pond, or into any mass of water, will produce the same effect on it. (Bain.) But in what does this conclusion consist? At the moment when, just before flinging the second stone, I infer the effect which it is going to pro- duce, what passes in my mind ? Is it not an inter- nal vision of the water, of the noisy splashes, and of those concentric waves which will be formed around the disturbed point? So the purpose of every reasoned conclusion appears to me to be to make us sec, by the mind's eye, the object or the fact which the conclusion affirms. The person who reasons, meditates in order to behold within himself, in a sort of magic lantern, the images which pass and the pictures which are formed. Reasoning produces a kind of logical vision which fills the gaps in actual vision ; it constructs a new universe in our mind on the model of the large. In short, such is the aim of knowledge: to know, to understand, to explain, to know the why and the how of things, all this culminates in an act of vision. The highest science is epitomized in these simple words : to see. Memory, which preserves the impressions of the senses, reproduces them at the necessary moment, and localizes them in their places in the picture of the past, might justly be called, like reasoning, a supplementary sense ; more exactly, memory is a vision of the past, while reasoning is, in general, a prevision — that is to say, a vision of the future. These conclusions are confirmed by the previous experiments on the consecutive image, which lead CONCLUSION. 173 US to see in the visual centre a retina whose every point is represented in the peripheral retina. The expression "the mind's eye" ceases to be a meta- phor, and the field of the mind is as if counterdrawn from the visual field. In fact, while experimenting on the transferred consecutive image, we see that this image, which, like a recollection, is cerebral, has definite dimensions, height and depth, a right side and a left side, and a position in the field of vision, properties which prove to be common to all the images of the mind, and render the relation between the image and the sensation still more intimate. III. Three images which succeed each other, the first evoking the second by resemblance, and the second suggesting the third by contiguity — that is reasoning. Submit any reasoning to analysis, and you will find nothing else at the bottom of the crucible. But it would be an error to believe that this process belongs specially to reasoning. Far from it. We meet it in all intellectual operations; it is the single theme upon which nature has em- broidered the infinite variations of our thought. The two well-known laws of the association of ideas are at the basis of psychology. They are, according to John Stuart Mill, Mr. Bain and Mr. Sully, blended together in so intimate a fashion that neither of them can ever act alone. Let us consider a case of similarity properly so called, a portrait recalling the original ; in order that the two 174 T'HB PSrCHOLOGT OF REASONING. similar images may not be confounded the one with the other, the second must present features which are sHghtly different; and how will these differ- ential characteristics be recalled? By contiguity. Here we recognize our three images and our two relations of resemblance and of contiguity. In order that a relation of resemblance may be per- ceived, it must be followed by a relation of conti- guity. Let us then examine a case of contiguity. What is necessary, asks Mr. Bain, in order that the sight of a river should recall its name to us? It is necessary that the actual impression made by the river restores, by virtue of similarity, the former impression of the river to which the former impres- sion of the name was contiguous. Suppose that this revival of the old idea of the river does not take place upon the new presentation, then the bond of contiguity will not have an opportunity to enter into play. In this case we again find our three images and our two relations. In order that a relation of con- tiguity may become known, it must be introduced by a relation of resemblance. How does it happen that these ideal recollec- tions are not reasonings, although they have their structure? To tell the truth, I do rot in the least know. Perhaps we ovight to appeal to what Lewes called the attitude of the mind ; in a simple associa- tion of ideas we only interest ourselves in the hint of a new image; in reasoning, on the contrary, we take more account of the association which this new image contracts with the preceding one. CONCLUSION. 175 The formation of a general idea presen-ts the same phenomenon of iso'merisvi ; we know that it arises from the union of several particular images which are welded together by their common por- tions; the total operation is therefore composed of an association of resemblance followed by an asso- ciation of contiguity ; it is the same familiar pro- cess. But here we find, between the general idea and reasoning, a logical affinity which explains this unity of composition; the general idea is a reason- ing in embryo; to generalize any object is to affirm something in addition to the result of a single ex- perience. The general idea of a tree contains more elements than the vision of an isolated tree; it contains an implicit conclusion. All these phenomena are like the first outlines of reasoning. There are others, much more complex, which show the same mental composition. In order not to lose ourselves in too lengthy develop- ments of our subject, we shall remain within the limits of the study of external perception. So far, we have admitted that every perception results from a reasoning. This proposition is only true in general. In reality, many other acts may take the form of a perception — that is to say, man- ifest themselves directly after an impression of the senses. We may find in perception — first, an act of recollection ; second, an act of imagination. First. — There is no well-defined distinction be- tween a perception-recollection and a perception- reasoning. "To the psychologist," says Mr. Sully, "it comes to very much the same thing whether, I7<5 THE PSrCHOLOGT OF REASONING. for example, on a visit to Switzerland, our minds are occupied in perceiving the distance of a moun- tain or in remembering some pleasant excursion which we made to it on a former visit. In both cases there is a reinstatement of the past, a repro- duction of earlier experience, a process of adding to a present impression a product of imagination — taking this word in its widest sense. In both cases the same laws of reproduction or association are illustrated ; that is to say, an association of resem- blance followed by an association of contiguity." Further on the author adds a remark which proves how frequent this phenomenon is. "And our state of mind in recognizing an object or person is com- monly an alternation between these two acts of separating the mnemonic image from the percept and so recalling or recollecting the past, and fusing the image and the percept in what is specifically marked off as recognition."* In what respect does a recollection differ from a reasoning? This is difficult to determine. We grasp the analogies between these two acts much more easily than their differences. All that the most attentive observation teaches us is that some- times the suggested image is projected and localized in the panorama of the past, of which it appears to be a fragment, and sometimes it is referred to a present object, and throws off its character of old- ness, so as to appear actual. Second. — We have already spoken of imaginary perceptions. These are by no means rare facts, *0p. cit., p. 235. CONCLUSION. 177 mere idle recreations; we necessarily see in them one of the forms of that desire for agreeable illu- sions which appears to be inveterate in us, for we meet it in the adult man, in the manifestations of art, in children, in their games (hide-and-seek, sham fighting, the doll, etc.), and even among young ani- mals, in their mimic combats. Analysis shows that these voluntary illusions are constructed according to the same processes as correct perceptions; an association of resemblance followed by an associa- tion of contiguity. As to their distinctive characters, they are only to be found in the attitude of tJie self which accompanies sensory perception. The mind knows that it has to deal with an illusion; it does not take it seriously. One understands that it would be extremely difficult to analyze so complex a psychical state. And now, how are we to explain this unity of composition among intellectual acts which have such different duties to perform? We believe that it is necessary to introduce the theory of evolution here. It seems to us probable that all psychical phenom- ena, so varied when we take them in the adult civil- ized man, have sprung from a common stock, and that they owe to that their unity of composition. But what can really be, in the three facts which we are comparing, the primitive fact to which the two others may be referred. It is that which is most necessary to the animial in its struggle for existence : reasoning. In fact, reasoning is, as we have said, a supple- mentary sense, freed from the conditions of time lyS THE PSrCHOLOGT OF REASONING. and space. We have by means of reasoning the sensation of external objects before they come into contact with our organism, which permits us to know in advance what conduct we must adopt; whether it concerns the animal in pursuit of food, in quest of the female, or in the interests of de- fence, reasoning, and perceptive reasoning in partic- ular, is the basis of a preadaptation of the individ- ual to its environment. Memory, as a vision into the past, offers less utility than reasoning; we have more frequent need to look before than behind ; it is a kind of intellect- ual refinement to contemplate the things of the past as past, and without making them serve in the explanation of present facts. Therefore it seems to us probable that memory is not a primitive, but a superadded fact ; it has sprung from reasoning at a time when the struggle for existence became less imperious. The same may be said of imagination, as a faculty of creating assemblages of images which do not correspond to any external reality. This faculty must belong to an advanced stage of devel- opment, for it is not directly useful in adaptation. Before taking pleasure in fictions, it was necessary to think of food, reproduction and defence. There- fore we must connect imagination with reasoning; it is reasoning deviated from its end, falsified, creat- ing chimeras which we do not seek to rectify, because they please us; thus a statue is a fiction of which we like to be the dupe. To sum up, all forms of mental activity are CONCLUSION. 179 reducible to a single one — reasoning. The psy- chical life is a continual conclusion. Tlie mind, as Wundt says, is a tJmig which reasons. IV. The preceding theory explains reasoning by the properties of images and sensations, and by these properties alone. It introduces nothing else ; there- fore the expression "I reason," which is employed so often, is, taken literally, to a certain extent wrong. A collection of facts of consciousness — the self is nothing else — can have no action whatever on one fact of consciousness in particular. It is quite as incorrect to say that judgment is the act by which the mind compares. It is as if we said that chemical combination was the act by which chemistry unites two bodies. Just as the combina- tion of the bodies results directly from their proper- ties, so mental combinations, and reasoning in par- ticular, result directly from the properties of images. We may here repeat what M. Ribot has said of the voluntary act:* "The 'I will,' " he has re- marked, "testifies to a condition, but does not pro- duce it. The volition that subjective psychologists have so often observed, analyzed and commented upon, ... is not the cause of anything. The acts and movements which follow it result directly from the tendencies, feelings, images and ideas which have become coordinated in the form of a choice. It is from this group that all the efifi- cacy comes." The accuracy of this point of view *Diseases of the Will (Open Court Pub. Co., Chicago), p. 133. I So THE PSrCHOLOGT OF REASONING. is still more apparent, if that were possible, in the sphere of reasoning. The idea which we form of reasoning, the attributing of this operation to our self, to our personality, is a superadded phenome- non, and not an essential part of the operation. The "I reason" is not a cause, it is an effect. It is wanting in the child, in ignorant persons and in the millions of people who have never studied psy- chology. They have never tried to give an account of the fact that they reason, and of how they set about to reason. They are indifferent in the matter; they are content to reason without considering how they do it. The intransigeants of psychology, those who push everything to extremes, have maintained that we must say, It reasons in iny brain, as we say, It thunders in the sky. These expressions are not only ridiculous, they are inaccurate, which is worse. The formation of a self, as the centre and subject of all psychical phenomena, is not a matter of conven- tion ; it is a natural phenomenon, which is realized in every man. We must not therefore eliminate it. M. Richet has observed that in experiments on hypnotic suggestion, we may abolish and metamor- phose the personality of the subject without for all that suppressing his self, which proves that the two things are distinct. When we transform the sub- ject into a soldier, a dancer, a child, a bishop, or a goat, he adopts the language and the gestures of these different roles, but he does not cease to say "I" in speaking of his sensations and of his acts, to have a self — that is to say, a kind of point of CONCLUSION. l8l insertion for all the sensitive and motor impressions which take place within him. (Richet, La person- nalite et la inhnoire dans le soinnainbulisme, Revue philosopkigue, March, 1883.) So far nothing has been said of the principle or postulate which should be implied, according to many thinkers, in every kind of reasoning, and would justify the passage from the known to the unknown. The study of these principles holds an important place in treatises on logic. For example, the postulate of every induction would be the uniformity of the course of nature. In fact, it is said, in order to believe that what has been pro- duced in a particular case will be reproduced in all similar cases, it is necessary to believe previously that ''there are such things in nature as parallel cases; that what happens once, will, under a suffi- cient degree of similarity of circumstances, happen again, and not only again, but always."* It was long ago answered that the uniformity of the laws of nature was not taught us by a super- natural revelation ; it is a very complex piece of knowledge, which is wanting in the majority of men, and which, among those who possess it, is formed late, by a slow accumulation of partial inductions. To postulate the result of a particular induction, which is neither constant, nor elemen- tary, nor primitive, as the foundation of our induc- tions would therefore be to reason in a circle. The real foundation of reasoning must be sought in the psychical law which governs it. The *John Stuart Mill, Logic, Book III, Chap. III. 1 82 THE PSrCHOLOGT OF REASONING. organization of our intelligence is so arranged that when the premisses of a reasoning are stated, the conclusion results from them with the necessity of a reflex action. In other words, we reason because we have in our brain a machine for reasoning. The legitimacy of our inferences has not a rational basis; it is not proved, for every demonstration presup- poses the legitimacy of the reasoning. This is a common sense truth. Let us be more precise ; in reasoning, the primary role belongs to the images ; it is the images which arrange themselves, in reasoning, by virtue of the properties which they manifest when they are brought before the mind ; it is they which sponta- neously form, to our internal sight, the picture of the external world. This conception is directly derived from the facts which fill this book. We have shown that similarity is a property of images, and we have said with M. Pilon that we must distinguish between the action of resemblance and the perception of resemblance. (See p. 127.) From this important distinction it follows that the suggestion of similar images is a primary fact of automatism; that the union and fusion of similar images into a generic image is a second fact of automatism ; and that the organization of similar images into reasoning is a third fact of automatism. In all these cases the self only intervenes when the work is finished. Just as "the resemblance between two images is only perceived after their suggestion" (Pilon), so the CONCL US ION. I §3 reasoning which they form in becoming organized is only perceived after its formation. If it were necessary to make use of a comparison in order to describe the mechanism of reasoning, we would mention those flowers which are formed dur- ing frost on the window panes of rooms. Let us thaw them with our breath and then observe the regelation of the liquid layer. While crystallization is taking place round a first crystal "you notice one feature which is perfectly unalterable, and that is, angular magnitude. The spiculae branch from the trunk, and from these branches others shoot ; but the angles enclosed by the spiculae are unalter- able."* Just as these crystallizations are produced by the forces inherent in each of the molecules, so reasoning is produced by the properties inherent in each of the images; just as crystallization, in its oddest eccentricities, always observes a certain angular value, so reasoning, true, false or insane, always obeys the laws of resemblance and of conti- guity. This being admitted, reasoning may become unconscious without our being obliged to infer a profound change in the phenomena. When it is admitted that reasoning results from a faculty of the soul, is there any more embarrassing question than to explain the unconsciousness of certain reasonings? From our point of view nothing is more simple. Reasoning is a synthesis of images. Images are the psychical part of a psycho-physio- logical whole ; if they are wanting, the physiological *Tyndall, Light, p. loi; American Ed., p. 104. 184 THE PSrCHOLOGT OF REASONING. process remains ; it alone is essential, and it is suffi- cient. The physiological mechanism acts, as if it were accompanied by its epiphenomenon, con- sciousness; it does its work noiselessly, and as surely arrives at the final result. We are not able to describe this physiological process. Here we are still in the region of hypoth- eses ; we append a schema which will serve merely to fix our ideas. To limit the question, let us take the visual perception of a particular object. Every perception implies anterior states which are preparatory to it. In order that we should be able to perceive the object which is before us, to recognize its nature, its use, etc., it is necessary that, through preceding experiences, we should have associated in our mind the visual image of this object or of another of the same kind, with the train of images of all sorts which constitute our knowl- edge of it. How shall we express the product of these anterior experiences in physiological terms? Images have the same cerebral seat as sensations; we may suppose that each of them results from the excitation of such and such a group of cells taken in the sensory centres of the surface layers. Let us denote the visual image of the object by «B; these two letters will represent the two cells of the centre of vision which are supposed to vibrate when we imagine the object visually; by C D E F G H we shall denote the cells which serve as substra- tum to the other images of the object, tactile, muscular, etc., images. C ONCL US ION. 1 85 So far the hypothesis raises no difficulties. But we have so far eHminated an essential element, the relations. Psychological analysis proves that a bond of association exists between the different images of an object; it is this bond which gives the group its coherence and its unity, and which enables one of the attributes of an object to suggest the others, as when the voice of a person recalls his countenance. How can we translate this associa- tion physiologically? How are two impressions, of sight and hearing for instance, bound together in the brain? For that to be the case it is necessary that they be not restricted, the one to the visual centre and the other to the auditory centre. It has been assumed that when two groups of cells — the substratum of two images — are excited at the same time, the nervous wave circulates from one group to the other through those communicating fibres which are so numerous in the brain. So, as M. Fouillee says, do the two undulations produced in a mass of water by two stones dropped at a small distance apart come to meet each other. From this fact it follows that the path between the two groups of cells under consideration is rendered easier for future waves, and that when, later on, one of the two groups will be alone excited, the current leaving it will follow that way in preference to any other, as being the line of least resistance. (Spencer.) In this way the elementary fact of the association of ideas has been translated into physi- ological terms. It has been said that groups of lS6 THE PSYCHOLOGY OF REASONING. cells excited at the same time are united by dynam- ical associations (Ribot), or, again, form a single and individual clicJii. (Taine.) Thus in our example a dynamical association exists between the cells «B corresponding to the visual image of the object, and the cells C D E F G H corresponding to the mechanical sensations which the object gives when it is taken hold of. Let us add one touch more, and the hypothesis is complete. We have not spoken yet of the excitative sensation which must cause this associa- tion of cells to vibrate. Analysis has taught us that in external perception the sensation always resembles in part the first image which it evokes — that is to say, the anterior vision or visual recollec- tion of the same object, which we have denoted by ^B. We may therefore denote the cells which will vibrate under the influence of the actual vision by the letters A*^. The small a in this formula is the name of the element common to the actual vision and to the past vision ; for we know that the psy- chical quality of resemblance has identity of seat as its physiological correlative. When the vision begins, the nervous wave, after having traversed the group of cells Ka, passes into the group «B, by means of the cellular junction afforded to it by the cell a. In psychological terms, the vision of the object first of all recalls, by simil- arity, its visual recollection. Then the nervous wave continues its path by means of the preestab- lished dynamical associations, and it spreads itself CONCLUSION. 1S7 among the groups of cells denoted by C D E F G H ; at the same time the recollection of all the old experiences rises in the mind ; this wave of images becomes associated with the vision of the moment, and the psychical synthesis is formed. Certainly such a conception of the action of the nerve centres is a true hypothesis; we have no means whatever of observing what occurs in the brain of a thinking man. All that we can affirm is that reasoning might be effected by the mechanism described, for our neuro-physiological hypothesis is traced from the subjective analysis of reasoning. Thus reasoning might be defined from the physio- logical point of view as the continuation of a process whose first phase (the excitation of the cells Ad) is the only one which corresponds to an external stim- ulant. This is the counterpart of the psychological definition: reasoning is an extension of experience. We leave to the reader the care of deciding whether this mechanical theory removes all activity from the mind, so as to reduce it to a purely passive state. This is a reproach which has often been made against the English school, which tries to explain all the phenomena of the mind by the laws of association. But to what extent is this reproach well-founded? Images are not by any means dead and inert things; they have active properties; they attract each other, become connected and fused to- gether. It is wrong to make the image into a photographic stereotype, fixed and immutable. It is a living element, something which is born, some- l88 THE PSrCHOLOGT OF REASONING. thing which transforms itself, and which grows like one of our nails or our hairs. Mental activity results from the activity of images as the life of the hive results from the life of the bees, or, rather, as the life of an organism results from the life of its cells. THE END. INDEX. Achromatopsia, 34. Agraphia, 25. Alcoholic delirium, 134. Ampere, 121. Anaesthesia, systematised,73,76. Aphasia, motor, 25. Aristotle, 1, 87. Association, laws of, 92. Auditifs, 23. Baillarger, 48. Bain, Alexander, 4, 41, 43, 96, 119, 144, 172, 173, 174. Ball, 61. Beclard, 44. Bersot, 166. Beyle, 115. Binet, 26, 43, 60, 73. Blindness, verbal, 26. Boole, 152. Brochard, 2, 90, 129. Brewster, 61. Charcot, 17, 27, 31. Chromatic contrast, 39. Circle of sensation, 105. Clifford, 112. Color blindness, 34. Coloured hallucinations, 35, Composite portraits, 116. Consciousness, intermediate state of, 139, 148. Contrast, chromatic, 39. Cycle, visual, 114. Da Vinci, Leonardo, 136. De Boismont, Brierre, 53. Delboeuf, 116. Delirium, alcoholic, 134. Diplopia, hallucinatory, 62. Euler, I. Evolution, theory of, 177. Experiment, mirror, 66. Experiments in hypnotism, 31. F^r^. 26, 39, 37, 40, 42, 61, 63, 73. 167. Fouillee, 185. Fusion of similar images, the, 113- Fusion, laws of, 108. Galton, II, 15, 24, 25. 113, 116, 118. Genesis of external perception, 129. Goethe, 114. Hallucinations, coloured, 35 ; hypnotic, 56 ; induced. 32 ; igo THE PSYCHOLOGY OF REASONING. suggested, 33 ; toxic, 135 ; visual, 38. Helmholtz, 8, 39, 50, 88, 143. Hemi-ansesthesia, 34. Henslow, Rev. George, 113. Huxley, 116. Hypnotism, experiments in, 31. Illusions, of the senses, 5, 60, 89, 130; passive, 89; volun- tary, 177. Images, consecutive, 44, 172 ; consecutive and real, com- pared, 49; defined, 8, 31 ; dif- ferent kinds of, 13 ; generic, 116; localisation of the, 37; motor, 24 ; physiology of the, 31 ; physiological properties of, 43 ; psychological nature of, 10 ; seat of, 31 ; the fu- sion of similar, 113 ; theory of three, 158 ; sensations and, combination of, 68. Imagination, 178. Indifferents, 14. Induced hallucinations, 32. James, William, 24, 157. Janet, Paul, 2, 4. Lachelier, 5. Laird, Louis, 140. Lewes, 123. Localisation of the image, 37. Londe, 59. Lotze, 120. Magnan, 115, 135. Maury, 116, 129. Memory, 172, 178. Mill, John Stuart, i, 2, 79, 92, 96, 98, 102, 144, 145, 152, 154, 173, 181. Mirror experiment, 66. Moteurs, 23. Motor aphasia, 25. Motor image, 24. Nature, uniformity of the course of, 181. Nerve-fields, theory of, 106. Nev/ton, 48. Oscillations, consecutive, 42. Paraphrasia, 125. Parinaud, 39, 40, 44, 46, 47, >54. Paulhan, 29, 7b. Percept, 69, 78, 160. Perception, defined, 4, 8 ; dif- ferent kinds of, 70 ; external, 56, 69, 81, 151 ; genesis of ex- ternal, 129; imaginary, 135; individual and generic, 73 ; mechanism of, 142 ; psycho- logical nature of, 80. Physiology of the image, 31. Pilon, 121, 127, 182. Portraits, composite, 116. Pouchet, 117. Properties of images, physiolo- gical, 43. Psychological nature of images, 10. Reasoning, defined, 86, 93, 149; 156 ; explanation of, 91 ; fac- ulty of, 95 ; formal, 81 ; foun- dation of, 181 ; function of, 165 ; purpose of, 171 ; psy- chological mechanism of, 184 ."^ true theory of, 96 ; uncon- scious, 80. INDEX. 191 Renouvier, 157. Representations, 7. Retrogression, law of , 76. Ribot, 24, 76, 91, 96, 102, 124, 179, 186. Richer, 52, 73, 82, 170. Richet, 168, 180. Schopenhauer, 167. Sensation, circle of, 105. Sensations and images, combi- nation of, 68. Senses, illusion of the, 5, 60, 89, 130. Simon, Max, 115. Somnambulists, 166. Sophism, 89. Spencer, 43, 79, 84, 88, 93, 97, 119, 125, 162, 185. Strieker, 27. Suggested hallucinations, 33. Sully, 70, 89, 116, 144, 173, 175. Syllogism, i, 80, 84, 97, 151, 159, 162. Taine, 2, 10, 11, 15, 48, 60, 96, 186. Toxic hallucinations, 133. Trousseau, 147. Verbal blindness, 26. Visual cycle, 1I4. Visual hallucination, 38. Weber, 103, 118. Wigan, 16. Wundt, 4, 40, 96, 121, 146, 156, 179. Zootrope, 112. THE OPEN COURT A MONTHLY MAGAZINE Devoted to the Science of Religion, the Religion of Science, and the Extension of the Religious Parliament Idea. THE OPEN COURT does not understand by religion any creed or dog- matic belief, but man's world-conception in so far as it regulates his conduct. The old dogmatic conception of Religion is based upon the science of past ages; to base religion upon the maturest and truest thought of the present time is the object of The Open Court. 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