One of the simplest ways of approaching the problems of 'extension’ and ‘intension’ is perhaps to point its connection with definitions. A collection may be defined, so we are told, by enumeration of its members, as, for instance, when we say that the collection contains Smith, Brown, Jones,. Or we may define our collection by giving a defining ‘property’. We are told that the first type of definitions which enumerates individual members is to be called a definition by extension, the second, which gives a defining ‘property’, is to be called a definition by intension.
We can easily see that a 'definition by extension' uniquely characterizes the collection, Smith1 Brown1 Jones1,. Any other collection, Smith2, Brown2, Jones2., would obviously be different from the first one, since the individuals differ. If we ‘define’ our collection by intension; that is, by ascribing some characteristic to each of the individuals, for instance, that they have no tails, many collections of individuals without tails might be selected. Since these collections would be composed of entirely different individuals, they would be entirely different, yet by ‘intension’, or defining characteristic, they all would be supposed to be one collection.
A. Korzybski, Science and Sanity, p. 173
In any of several studies that treat the use of signs - for example, in linguistics, logic, mathematics, semantics, and semiotics - the extension of a concept, idea, or sign consists of the things to which it applies, in contrast with its comprehension or intension, which consists very roughly of the ideas, properties, or corresponding signs that are implied or suggested by the concept in question.
In philosophical semantics or the philosophy of language, the 'extension' of a concept or expression is the set of things it extends to, or applies to, if it is the sort of concept or expression that a single object by itself can satisfy. <...>
So the extension of the word "dog" is the set of all (past, present and future) dogs in the world: the set includes Fido, Rover, Lassie, Rex, and so on. The extension of the phrase "Wikipedia reader" includes each person who has ever read Wikipedia, including you.
http://en.wikipedia.org/wiki/Extension_(semantics)
vseslavrus в посте Metapractice (оригинал в ЖЖ)
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