QUASI-INDEXICALS AND KNOWLEDGE REPORTS

We present a computational analysis of de re, de dicto, and de se beli ef and knowledge reports. Our analysis solves a problem first observed by Hector-Neri Castaneda, namely, that the simple rule '(A knows that P) implies P' apparently does not hold if P contains a quasi-indexica l. We present a single rule, in the context of a knowledge-representat ion and reasoning system, that holds for all P, including those contai ning quasi-indexicals. In so doing, we explore the difference between reasoning in a public communication language and in a knowledge-repres entation language, we demonstrate the importance of representing prope r names explicitly, and we provide support for the necessity of consid ering sentences in the context of extended discourse (e.g., written na rrative) in order to fully capture certain features of their semantics .