Abstract
It is often said that a person P knows the meaning of a sentence S if P knows S’ s truth-conditions, in the sense that given any possible world, P knows whether S is true in that world. This idea of sentence-meaning corresponds fairly closely to what Frege, Russell, Carnap, and other philosophers have had in mind in speaking of the senses, propositional contents, or “locutionary” meanings of sentences; and, not unnaturally, it has encouraged semanticists such as David Lewis, Robert Stalnaker and Max Cresswell to suggest that sentence-meanings or propositions simply are functions from the set of possible worlds onto the truth-values.