H. P. Grice virtually discovered the phenomenon of implicature (to denote the implications of an utterance that are not strictly implied by its content). Gricean theory claims that conversational implicatures can be explained and predicted using general psycho-social principles. This theory has established itself as one of the orthodoxes in the philosophy of language. Wayne Davis argues controversially that Gricean theory does not work. He shows that any principle-based theory understates both the intentionality of what a speaker implicates and the conventionality of what a sentence implicates. In developing his argument the author explains that the psycho-social principles actually define the social function of implicature conventions, which contribute to the satisfaction of those principles. This challenging book will be of importance to philosophers of language and linguists, especially those working in pragmatics and sociolinguistics.