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<Paper uid="C88-1052">
  <Title>Presuppositions as Beliefs</Title>
  <Section position="2" start_page="0" end_page="0" type="intro">
    <SectionTitle>
1 Introduction
</SectionTitle>
    <Paragraph position="0"> 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 &amp;quot;&gt;&gt;&amp;quot;, are one pa~'t of that information. Table 1 gives several examples of presupposition with their traditional analyses 1.</Paragraph>
    <Paragraph position="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.</Paragraph>
    <Paragraph position="2"> Other types of pragmatic inference include entailment, conversational implicature, and conventional implicature (see Levinson (1983) for detailed descriptions). Presuppositions 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.</Paragraph>
    <Paragraph position="3">  sentation of ouc approach.</Paragraph>
    <Paragraph position="4"> Horton (1987) reviews several theories, including those of Karttunen (1973, 1974), Karttunen and Peters (1979), Wcischedcl (1975, 1979), Gazdar (1979a, 1979b), Wilson and Sperber (1979), and Atlas and Levinson (1981). 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.</Paragraph>
    <Paragraph position="5"> * Shared Belief Assumption: If sentence S (or its utterance) presupposes proposition P, then all agents  involved share the prior belief that P is true.</Paragraph>
    <Paragraph position="6"> Weischedel and Gazdar are exceptions; e~tch of them attributes presuppositions to the speaker as either knowl-. edge or belief. However, we will show th~tt the beliefs of agents other than the speaker must be considered in order to correctly express many presuppositions. Our ai)proach is to treat presuppositions as beliefs, but a.lso to consider the beliefs of all agents involved in discourse.</Paragraph>
    <Paragraph position="7"> A second difl~culty has been in finding an adequate definition of presupposition. Many definitions state that the presuppositions of a sentence must be known prior to the utterance of that sentence to avoid infelicity. Some have the stronger constraint that the presuppositions must be mutually known by all participants. The following definition (Levinson 1983, 205) has these properties:</Paragraph>
  </Section>
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