Despite living in a tradition-bound world of social hierarchies, many seventeenth-century Catholic clerics advocated for young men and women the "freedom" to "choose a state of life," in response to a "vocation," God's act of calling. Moreover, although most present-day commentators associate lay vocation with early modern Protestantism, these Catholic writers did not limit the concept of vocation to clerics or to those taking religious vows. Rather, every young Catholic had a calling, even to the lay (especially married) state. And since all were called by God, all had to take care to discover God's particular will for them. Failing to do so would imperil both their temporal happiness and their eternal salvation. The new seventeenth-century advice literature on choosing a state inspires intriguing questions relevant to the history of French Catholicism, of Catholic Reform more generally, and of French social and political life. Why were Catholic clerics so convinced about the importance of choosing a state of life? What did this process of choosing a state of life look like, in the ideal? What brought into being this advice literature? And what does this phenomenon reveal about France and about Catholicism in the early modern period and beyond? This dissertation argues that seventeenth-century vocational discernment advice developed from several strands of the medieval Catholic tradition and of Catholic Reform in the sixteenth century, and this advice literature gained particular traction in the rigorist milieu of mid-seventeenth-century France, where Catholic promoters of vocational thinking saw their advice as essential to solving the spiritual problems of individuals and of society as a whole. This advice on choosing a state of life illustrates the peculiar modernity of early modern Catholicism, which focused on the individual without jettisoning corporate identity, which held in tension the subjective good for the individual and an objective spiritual hierarchy, and which promoted a religiously-oriented individual liberty in the face of entrenched social and legal norms. The main source bases are works of spiritual advice and pastoral care from the early Middle Ages to the twentieth century, along with religious biographical sources and ecclesiatical records.