The renowned philosopher Jerry Fodor, a leading figure in the study of the mind for more than twenty years, presents a strikingly original t heory on the basic constituents of thought. He suggests that the heart of cognitive science is its theory of concepts, and that cognitive sc ientists have gone badly wrong in many areas because their assumptions about concepts have been mistaken. Fodor argues compellingly for an a tomistic theory of concepts, deals out witty and pugnacious demolition s of rival theories, and suggests that future work on human cognition should build upon new foundations.