As interest in the study of natural languages has increased, philosophers of language and logicians have, along with linguists, begun to pay more attention to sentences whose truth value varies from context to context. Alternatively, to sentences which are such that, if different speakers utter them, those speakers may (or sometimes must) say different things. For example, it is well-known that two different people who utter ‘I am hot’ will be saying different things, that two different people who utter ‘Billy is a lush’ may be saying different things, and that different speakers who utter ‘The book on the table is boring’ may say different things. The same sort of familiar point could be made by examples concerning other pronouns, demonstratives, the utterance of ambiguous sentences, and so on.