The early Greeks and the early Romans, in the bright joyousness or the laborious activity of objective life, fully occupied by the pleasures of art or the business of war and politics, with no minutely-detailed code or body of traditions to guide them, troubled themselves little about such problems. When, however, the Greek philosophers and their Roman followers developed moral systems, attention began to be given to this department; at length, such questions as how far suicide is justifiable, or whether duty to the state is more important than duty to a friend, became favourite subjects of debate; and, during the first two centuries of the Christian era, elaborate treatises on the subject were produced by the famous Stoic philosophers Epictetus, Seneca, and M. Aurelius.
Christianity brought in a new method of settling casuistical questions—a method directly opposed to that of most of the Jewish scribes, in the midst of whom it had its origin, and consisting in an appeal to the true spirit of great principles. Naturally this method would have left particular cases to the decision of each man's conscience; but the extreme recoil from reckless self-indulgence which gave birth to the monastic ascetic system produced a new kind of casuistical literature. It found its first great representative in Tertullian, a contemporary of M. Aurelius, with whom nearly all sin was mortal, one repentance at most being possible after baptism. The same type of casuistry was taught by others of the fathers, but with the greatest acuteness and power by Augustine, who laid special stress upon the subjective or spiritual side of Christian ethics, insisting upon the principle that the moral worth of action depends upon the disposition of the agent as much as upon the objective nature of the act.
In the Roman Catholic Church, the practice of confession gave rise to a system of casuistry, expressed in the Libri Pœnitentiales, which were intended to guide the confessor as to the imposition of penance and the giving of advice. Among the most important of these are the Summæ of Raimund of Pennaforti, Angelus, Antonius Augustinus, Pacificus, and Prierias, the work of the last (who was a vigorous opponent of Luther) being an alphabetical compilation from those of his predecessors. Later examples are Amort's Dictionarium casuum conscientiæ (1784), and Sobiech's Compendium theologicæ moralis pro utilitate confessariorum (1824). Indeed, throughout the Middle Ages, the doctrines of the church being universally accepted as the supreme rules of conduct, the casuistical was the department of moral science which was best developed. In Petrus Lombardus, in Alexander of Hales, and in Aquinas's famous treatise, the Secunda Secundæ, we find the uncompromising strictness of the ancient fathers but slightly modified. Abelard, though earlier, took a more indulgent view, but his teaching was condemned by the church, in the synod of Sens (1140).