|Extensionality, philosophy: (also extensionality principle, extensionality thesis) an attempt to make the language distinct by taking complete sets of denoted objects as the meaning of the referring words. See also extensions, intensions, extensional language, ambiguity, propositional attitudes.|
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Extensional language/Lewis: here we assume a language that is dexactly like the intensional one - only that there is an inaudible pause before each sentence - this corresponds to a q, which is the only (sentence-forming) predicate of the extensional language - then the intensional language Li be rich, while the corresponding extensional language Le is strictly extensional.
Then two field linguists could argue whether the natives speak an extensional or intensional language.
Die Identität von Körper und Geist Frankfurt 1989
Konventionen Berlin 1975
Philosophical Papers Bd I New York Oxford 1983
Philosophical Papers Bd II New York Oxford 1986
Cl. I. Lewis
Mind and the World Order: Outline of a Theory of Knowledge (Dover Books on Western Philosophy) 1991