Casuistry

Casuistry (/ˈkæʒuᵻstri/), or case-based reasoning, is a method in applied ethics and jurisprudence, often characterised as a critique of principle- or rule-based reasoning. The word "casuistry" is derived from the Latin casus (meaning "case").

Casuistry is reasoning used to resolve moral problems by extracting or extending theoretical rules from particular instances and applying these rules to new instances. The term is also commonly used as a pejorative to criticize the use of clever but unsound reasoning (alleging implicitly the inconsistent—or outright specious—application of rule to instance), especially in relation to moral questions (see sophistry).

The agreed meaning of "casuistry" is in flux. The term can be used either to describe a presumably acceptable form of reasoning or a form of reasoning that is inherently unsound and deceptive. Most or all philosophical dictionaries list the neutral sense as the first or only definition. On the other hand, the Oxford English Dictionary states 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 ("Casuistry‥destroys by Distinctions and Exceptions, all Morality, and effaces the essential Difference between Right and Wrong"). Most online dictionaries list a pejorative meaning as the primary definition before a neutral one, though Merriam-Webster lists the neutral one first. In journalistic usage, the pejorative use is ubiquitous.

While a principle-based approach might claim that lying is always morally wrong, the casuist would argue that, depending upon the details of the case, lying might or might not be illegal or unethical. The casuist might conclude that a person is wrong to lie in legal testimony under oath, but might argue that lying actually is the best moral choice if the lie saves a life. (Thomas Sanchez and others thus theorized a doctrine of mental reservation, which developed into its own branch of casuistry.) For the casuist, the circumstances of a case are essential for evaluating the proper response.

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