Abstract

This dissertation concerns the special cognitive significance of thoughts expressed with indexical terms, terms such as "I", "now", and "this". Indexical terms are given a structural definition in terms of context-sensitive semantics and a functional definition in terms of their capacity to express thoughts which identify and locate individuals "from a perspective", a manner of identification essential for prompting action. ;The dissertation includes two main projects. The first is to argue that indexically expressed thoughts are of limited accessibility, i.e., that such thoughts about an index are thinkable only at that index. The second is to argue that the special informativeness of indexically expressed thoughts lies not just in their distinctive content, but in this limit on their accessibility. ;To establish the thesis of limited accessibility, I need to argue against the narrow classification of thought contents advocated by methodological solipsism. I offer a scheme which preserves many of the intuitions motivating the solipsistic classification, but which classifies content broadly. ;The content of an indexically expressed thought is distinguished from that of its eternal but co-referential counterparts and is shown to be of limited access without introducing special concepts of individuals or of being present to associate with "I" or "now". ;The content assigned to indexically expressed thoughts is a species of propositional, semantic content, not functional role content. The account of the cognitive significance of these thoughts cites features of the semantic content to explain the behaviors generated, thus avoiding a bifurcation of traditional notion of belief between representational and functional classification of mental states. ;The limited accessibility account is compared to rival accounts of the cognitive significance of indexicals, including approaches which focus on the indexical expression, token-reflective semantics, special senses, the act of affirming, and the variability of truth value of sentences containing indexical terms