Extensional and intensional definitions: Difference between revisions

Revision as of 13:05, 3 April 2021

Revision as of 13:05, 3 April 2021

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{{Short description|Classification of definitions in mathematics, philosophy, and logic}}

In [[logic]], [[philosophy]], and [[mathematics]], '''extensional and intensional definitions''' are two key ways in which the [[Object (philosophy)|objects]], [[concept]]s, or referents a [[terminology|term]] refers to can be [[definition|defined]]. It gives [[Meaning (linguistic)|meaning]] or denotation to a term.

==Intensional definition==

{{also|Intension}}

An intensional definition gives the [[Meaning (linguistic)|meaning]] of a term by specifying necessary and sufficient conditions for when the term should be used. In the case of [[nouns]], this is equivalent to specifying the [[Property (philosophy)|properties]] that an [[Object (philosophy)|object]] needs to have in order to be counted as a [[referent]] of the term.

For example, an intensional definition of the word "bachelor" is "unmarried man". This definition is valid because being an unmarried man is both a necessary condition and a sufficient condition for being a bachelor: it is necessary because one cannot be a bachelor without being an unmarried man, and it is sufficient because any unmarried man is a bachelor.<ref name="Cook">Cook, Roy T. "Intensional Definition". In ''A Dictionary of Philosophical Logic''. Edinburgh: Edinburgh University Press, 2009. 155.</ref>