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Intensional language/compositionality/Lewis: here for intensional language: here it applies only to intensions, not to extensions. - Tradition: knew only extensional languages. - Intensional language: extensions depend on the context.
New: Intension-determining rules - allow composite modal operators and quantifiers. - If only intensional rules, the extensions disappear - then we only have semantic values of one level instead of two.
Intensional language: here teh sub-sentences are only S names (sentence names without truth value), no sentences.
Intensional language/extensional/Lewis: the difference is so hard to grasp that it hardly makes a difference which we use. - Greater difference: if a language can be formally analyzed or not. - Ontology: for it, it is only important whether suspect entities have to be assumed - which does not coincide with the difference internal/external.
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