Propositions for Semantics and Propositions for Epistemology

Abstract

The title is an allusion to the fact that, traditionally, propositions have served at least two distinct functions in philosophy, even though these functions have not usually been distinguished. Propositions have been invoked as the ‘meanings’ or ‘intensions’ of sentences and as the objects of propositional attitudes. Thus the proposition that Socrates is wise is themeaningof the English sentence, ‘Socrates is wise,’ and iswhatCharles believes when he believes that Socrates is wise. ‘Means that’ and ‘believes that’ take the same kind of object. I shall argue, first, that there are two quite different functions here and it takes two quite different kinds of proposition to serve these distinct functions. The second thing I want to do is examine the suggestion that we can treat propositions as sets of possible worlds. There is a serious difficulty here, and so I shall want to turn that idea on its side: I shall define possible worlds as sets of G-propositions (semantical propositions) and then define E-propositions (epistemic propositions) as sets of possible worlds.