Presuppositions as beliefs

Most theori~s of presupposition implicitly assume that pre-supposition,; are facts, and that all agents involved in a discourse share belief in the presuppositions that it generates. These unrealistic assumptions can be eliminated if each presupposition is treated as the belief of an agent. However, it ~s not enough to consider only the beliefs of the speaker; we show that the beliefs of other agents are often involved. We describe a new model, including an improved definition of presupposition, that treats presuppositions as beliefs and considers the beliefs of all agents involved in the discourse. We show that treating presuppositions as beliefs makes it possible to explain phenomena that cannot be cxplainecl otherwise. 1 Introduction In addition 'I;o its literM meaning, a sentence or utterance conveys a host of indirect information that can be pragmatically in~rred. Presuppositions, whidl we mark ">>", are one pa~'t of that information. Table 1 gives several examples of presupposition with their traditional analyses 1. Roughly, a presupposition is a proposition that is conveyed by a sentence or utterance 2 but is not part of the main point, and must be consistent with the established context in order for that sentence or utterance to be felicitous. For example, the following is infelicitous because the second .,~entence presupposes that Angle quit, which contradicts the first sentence: (1) *Angle didn't quit. It's surprising that she quit. Other types of pragmatic inference include entailment, conversational implicature, and conventional implicature (see Levinson (1983) for detailed descriptions). Presuppo-sitions can be distinguistmd from other sorts of pragmatic inference by their unique behavior when the sentence from which they originate is negated. These basic ideas are generally agreed upon; however, their formalization into a theory of presupposition has been difficult. We will now introduce two problems and our approach to solving them. 1 Throughout this paper, we use the sentence itself a.q short form for its semantic representation, in order to avoid addressing the orthogonal issu*., of semantic representation. 2The sentence/utterance distinction will be made clear in the presentation of ouc approach. One problem is that many theories of presupposition iiaplicitly make the' following unrealistic assumptions s: • Truth Assumption: If sentence S (or its utterance) presupposes proposition P, then P is true. • Shared Belief Assumption: If sentence S (or its utterance) presupposes proposition P, then all agents involved share the prior belief that P is true. Weischedel and Gazdar are exceptions; e~tch …