Over the course of the last twenty-five years, linguistic theory has established itself as providing one of the major routes towards an understanding of the human mind. With increasing precision we have been able to address the problem of articulating in detail the structured capacities the human mind brings to the problem of language acquisition. Along the way there have been doubters, much of the doubt having arisen because of the apparently unbridgeable gap the theory demands between the language user's capacity and the interaction of this capacity with more general cognitive skills. Such doubters as there were received little reassurance from looking at work on performance or language use, for there has been little more than speculative philosophy on the one hand (most notably by Paul Grice, 1975) and articulation of detailed processing mechanisms on the other (e.g. Fodor, 1978; Frazier, 1979; Frazier & Fodor, 1978), without any overall theory. J. A. Fodor (1982, 1983) has led the field in cognitive psychology with his representational theory of mind. But we have till now had no theory of the central cognitive mechanism. Relevance Theory (Sperber & Wilson, 1986) provides us with a contender. It makes specific claims about the central cognitive mechanism and about the relation of natural language to that central mechanism. Against this framework, we are at last able to formulate precise proposals about the grammar-cognition interface, and in so doing provide answers to the psychological reality questions which have gone unanswered for so long: What is the relation of grammars to utterance–interpretation? What is the nature of the link between grammars and the central cognitive mechanism? What is the relation between a speaker's knowledge of his language and his general knowledge?