Local Contexts: a Précis

For the last thirty years, it has been assumed that a presupposition must be entailed (or ‘satisfied’) by the context, construed as what is common belief between the speaker and addressee: John has stopped smoking is acceptable in a context C just in case C entails that John used to smoke. Technically, the context in this sense is often called the ‘context set’, identified with the set of possible worlds compatible with what the speech act participants take for granted; in this case, then, the requirement is that each world in C is one in which John used to smoke. In order to deal with the presuppositions of compound sentences, however, this analysis must be supplemented with a dynamic view of context change. This is because presuppositions are sometimes filtered out of complex sentences for instance the conjunction John used to smoke and he has stopped asserts rather than presupposes that John smoked. The standard explanation (Stalnaker 1974; Karttunen 1974) is that the second conjunct is not evaluated with respect to the initial context, but rather with respect to a ‘local context’, obtained by updating the initial one with the content of the first conjunct. Writing as C[H] the update of C with a formula H, the update rule for conjunctions is summarized in (1):