Casuistry (//) is a process of reasoning that seeks to resolve moral problems by extracting or extending theoretical rules from a particular case, and reapplying those rules to new instances. This method occurs in applied ethics and jurisprudence. The term is also commonly used as a pejorative to criticize the use of clever but unsound reasoning, especially in relation to moral questions (as in sophistry). The word casuistry derives from the Latin noun casus ("case" or "occurrence").
The Oxford English Dictionary says, quoting Viscount Bolingbroke, Viscount (1749), that the word "[o]ften (and perhaps originally) applied to a quibbling or evasive way of dealing with difficult cases of duty." Its textual references, except for certain technical usages, are consistently pejorative (e.g., "Casuistry destroys by distinctions and exceptions, all morality, and effaces the essential difference between right and wrong").
Casuistry is the "[s]tudy of cases of conscience and a method of solving conflicts of obligations by applying general principles of ethics, religion, and moral theology to particular and concrete cases of human conduct. This frequently demands an extensive knowledge of natural law and equity, civil law, ecclesiastical precepts, and an exceptional skill in interpreting these various norms of conduct." It remains a common tool for applied ethics.
Casuistry dates from Aristotle (384–322 BC), yet the zenith of casuistry was from 1550 to 1650, when the Society of Jesus used case-based reasoning, particularly in administering the Sacrament of Penance (or "confession"). The term casuistry or Jesuitism quickly became pejorative with Blaise Pascal's attack on the misuse of casuistry. Some Jesuit theologians, in view of promoting personal responsibility and the respect of freedom of conscience, stressed the importance of the 'case by case' approach to personal moral decisions and ultimately developed and accepted a casuistry (the study of cases of consciences) where at the time of decision, individual inclinations were more important than the moral law itself.
In Provincial Letters (1656–7) the French mathematician, religious philosopher and Jansenist sympathiser, Blaise Pascal vigorously attacked the moral laxism of Jesuits who used casuistic reasoning in confession to placate wealthy Church donors, while punishing poor penitents. Pascal charged that aristocratic penitents could confess their sins one day, re-commit the sin the next day, generously donate the following day, then return to re-confess their sins and only receive the lightest punishment; Pascal's criticisms darkened casuistry's reputation.
A British encyclopedia of 1900 claimed that it was "popularly regarded as an attempt to achieve holy ends by unholy means."
It was not until publication of The Abuse of Casuistry: A History of Moral Reasoning (1988), by Albert Jonsen and Stephen Toulmin, that a revival of casuistry occurred. They argue that the abuse of casuistry is the problem, not casuistry per se (itself an example of casuistic reasoning). Properly used, casuistry is powerful reasoning. Jonsen and Toulmin offer casuistry in dissolving the contradictory tenets of moral absolutism and the common secular moral relativism: "the form of reasoning constitutive of classical casuistry is rhetorical reasoning". Moreover, the ethical philosophies of Utilitarianism (especially preference utilitarianism) and Pragmatism commonly are identified as greatly employing casuistic reasoning.
The casuistic method was popular among Catholic thinkers in the early modern period, and not only among the Jesuits, as it is commonly thought. Famous casuistic authors include Antonio Escobar y Mendoza, whose Summula casuum conscientiae (1627) enjoyed a great success, Thomas Sanchez, Vincenzo Filliucci (Jesuit and penitentiary at St Peter's), Antonino Diana, Paul Laymann (Theologia Moralis, 1625), John Azor (Institutiones Morales, 1600), Etienne Bauny, Louis Cellot, Valerius Reginaldus, Hermann Busembaum (d. 1668), etc. One of the main theses of casuists was the necessity to adapt the rigorous morals of the Early Fathers of Christianity to modern morals, which led in some extreme cases to justify what Innocent XI later called "laxist moral" (i.e. justification of usury, homicide, regicide, lying through "mental reservation", adultery and loss of virginity before marriage, etc.—all due cases registered by Pascal in the Provincial Letters).
The progress of casuistry was interrupted toward the middle of the 17th century by the controversy which arose concerning the doctrine of probabilism, which stipulated that one could choose to follow a "probable opinion", that is, supported by a theologian or another, even if it contradicted a more probable opinion or a quotation from one of the Fathers of the Church. The controversy divided Catholic theologians into two camps, Rigorists and Laxists.
Certain kinds of casuistry were criticized by early Protestant theologians, because it was used in order to justify many of the abuses that they sought to reform. It was famously attacked by the Catholic and Jansenist philosopher Pascal, during the formulary controversy against the Jesuits, in his Provincial Letters as the use of rhetorics to justify moral laxity, which became identified by the public with Jesuitism; hence the everyday use of the term to mean complex and sophistic reasoning to justify moral laxity. By the mid-18th century, "casuistry" had become a synonym for specious moral reasoning. However, Puritans were known for their own development of casuistry.
In 1679 Pope Innocent XI publicly condemned sixty-five of the more radical propositions (stricti mentalis), taken chiefly from the writings of Escobar, Suarez and other casuists as propositiones laxorum moralistarum and forbade anyone to teach them under penalty of excommunication. Despite this papal condemnation, both Catholicism and Protestantism permit the use of ambiguous and equivocal statements in specific circumstances.
G. E. Moore dealt with casuistry in chapter 1.4 of his Principia Ethica, in which he claims that "the defects of casuistry are not defects of principle; no objection can be taken to its aim and object. It has failed only because it is far too difficult a subject to be treated adequately in our present state of knowledge". Furthermore, he asserted that "casuistry is the goal of ethical investigation. It cannot be safely attempted at the beginning of our studies, but only at the end".
Since the 1960s, applied ethics has revived the ideas of casuistry in applying ethical reasoning to particular cases in law, bioethics, and business ethics, so the reputation of casuistry is somewhat rehabilitated.
Pope Francis, a Jesuit, has criticised utilizing casuistry, "the practice of setting general laws on the basis of exceptional cases," in instances where a more holistic approach would be more appropriate.