ONT Intension & Extension
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| Intension & Extension
|
| The 'intension' of a concept consists
| of the qualities or properties which
| go to make up the concept.
|
| The 'extension' of a concept consists of the things
| which fall under the concept; or, according to another
| definition, the 'extension' of a concept consists of the
| concepts which are subsumed under it (determine subclasses).
|
| This is the old distinction between intension and extension,
| and coincides approximately with the distinction between
| a monadic 'propositional function' (q.v.) in intension
| and a 'class' (q.v.).
|
| The words 'intension' and 'extension' are also used in connection
| with a number of distinctions related or analogous to this one, the
| adjective 'extensional' being applied to notions or points of view which
| in some respect confine attention to truth-values of propositions as opposed
| to meanings constituting propositions. In the case of (interpreted) calculi
| of propositions or propositional functions, the adjective 'intensional' may
| mean that account is taken of modality, 'extensional' that all functions
| of propositions which appear are truth-functions. The extreme of the
| extensional point of view does away with propositions altogether and
| retains only truth-values in their place.
|
| Alonzo Church, in Runes, pages 147-148.
|
| Dagobert Runes (ed.), 'Dictionary of Philosophy',
| Littlefield, Adams, & Company, Totowa, NJ, 1972.
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