Abstract

Paul Grice coined the term "implicature" in his 1967 William James Lectures. A speaker implicates a proposition if it is part of what he or she communicates, but not part of what he or she literally says. For example, when you direct a stranger to a gas station, you implicate that it is open. This is communicated, but not literally said. The only viable theory of implicature in the philosophical literature is Grice's own theory, which appeals to a "cooperative principle" and a set of "maxims" to explain implicatures. The first chapter of this dissertation argues that Grice's theory does not produce detailed and testable predictions. The remaining three chapters develop a "plan-based theory of implicature", using ideas from computational linguistics. In Chapter Two, I consider the general problem of plan recognition, developing a representation for plans and rules for reasoning about them. Chapter Three discusses the key concept "a speaker's plan", and applies it to several of Grice's examples. Chapter Four extends the analysis to conversations whose point is to construct a domain plan