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Definition Systematic ambiguity/Frege/Hintikka: all of our expressions are systematically ambiguous; that is, they refer to different things depending on whether they are direct (transparent, extensional) contexts or indirect (intensional, opaque) contexts.
Semantics of possible worlds/HintikkaVsFrege: here there is no > systematic ambiguity, i.e. the expressions mean intensionally the same as extensionally.
E.g. to know what John knows is to know the worlds that are compatible with his belief, and to know which ones are not.
Extra-premise: for this, one must be sure that an expression in different worlds takes out the same individual.
Context: what the relevant worlds are depends on the context.
E.g. Ramses: here the case is clear,
On the other hand:
E.g. Herzl knew that Loris was a great poet
Additional premise: Loris = Hofmannsthal.
Jaakko and Merrill B. Hintikka
The Logic of Epistemology and the Epistemology of Logic Dordrecht 1989
J. Hintikka/M. B. Hintikka
Untersuchungen zu Wittgenstein Frankfurt 1996