Abstract

The concept of common ground---a set of propositions common to speaker and hearer that is presupposed in conversation---is fundamental to most treatments of communication. However, relatively little work has been done on the contribution of indexical and demonstrative utterances to common ground. Because the beliefs expressed by these utterances seem to be inherently perspectival, it is not clear whether or in what we sense we should think of these utterances as generating "mutual" beliefs. Yet there is clearly a sense in which we do have a mutual understanding of the beliefs they communicate, and of reasoning based on such beliefs. My dissertation describes the content communicated by demonstrative and indexical utterances in a way that is suitable for the rational reconstruction of inferences involving demonstrative and indexical beliefs and for defining what becomes mutual when such utterances occur. ;I argue that natural language belief ascriptions, causal accounts of content, structured propositions, and purely descriptive accounts of content are all either unsuitable for the task, or only accomplish part of it. I develop a rudimentary artificial language for articulating this content. It enables us to define conditions of various kinds on doxastically possible contexts, where "contexts" are essentially centered worlds. IP also incorporates reference to demonstrative intentions and their objects in a way that permits them to be explicitly represented and systematically related to descriptive conditions on sets of contexts . The cognitive content represented is conceived as a set of doxastically possible semantic values---essentially knowledge of semantic value---rather than itself a semantic value In the third chapter I use IP to define what it is for demonstrative and indexical beliefs to be shared and mutual, and give indicate the role they might play in a goal-based account of the planning and interpretation of utterances. In the last chapter I use IP to argue that an interpretation of Richard's steamroller problem in terms of a de re/de dicto ambiguity is superior to its rivals