Pragmatic Reasoning, Defaults and Discourse Structure

In this paper we investigate the rational foundations of pragmatic reasoning. For specificity, we’ll use a particular theory of discourse interpretation that combines an account of rhetorical structure with dynamic semantics. In particular we argue for a rich, linguistic notion of discourse context which we compute by means of simple defeasible rules in a nonmonotonic propositional logic. These defaults are linguistic in nature but have access to nonlinguistic domains of world knowledge that are encoded in a more complex nonmonotonic logic. Our approach takes as basic the idea that compositional and lexical semantics produce an underspecified logical form and that there’s a level of linguistic pragmatic reasoning that resolves underspecifications where possible, thus producing a more complete logical form for interpretation. We argue here that this assumption is reasonable from the standpoint of a general theory of rationality and we investigate particular justifications for the various pragmatic principles that the theory adopts using a variety of game theoretic techniques.