Presuppositions as nonassertions

It is commonly assumed that the assertion/presupposition distinction maps fairly directly onto the distinction between new and old information. This assumption is made doubtful by presupposing constructions that regularly convey new information: uniquely identifying descriptions, 'informative presupposition' it-clefts, reverse wh-clefts, announcements embedded under factives, nonrestrictive relatives. The presupposed content conveyed by these constructions can be regarded as part of the common ground only with an unconstrained principle of accommodation. But this reduces the claim that grammatical presuppositions are part of the common ground to vacuity. Presuppositions are a consequence of two factors. One is a tendency to limit assertion to one atomic proposition per rooted sentence. The other is the fact that almost any thought to be expressed will involve many atomic propositions. Depending on medium, genre and other contextual variables, new information will be presupposed if it is not necessary to assert it. The view is confirmed by evidence that written language, which would be expected to contain more new information per utterance than spoken language, contains a higher proportion of text in definite descriptions. (C) 2000 Elsevier Science B,V. All rights reserved.