Western philosophy has long been divided between empiricists, who argue that human understanding has its basis in experience, and rationalists, who argue that reason is the source of knowledge. A central issue in the debate is the nature of concepts, the internal representations we use to think about the world. The traditional empiricist thesis that concepts are built up from sensory input has fallen out of favor. Mainstream cognitive science tends to echo the rationalist tradition, with its emphasis on innateness. In Furnishing the Mind , Jesse Prinz attempts to swing the pendulum back toward empiricism. Prinz provides a critical survey of leading theories of concepts, including imagism, definitionism, prototype theory, exemplar theory, the theory theory, and informational atomism. He sets forth a new defense of concept empiricism that draws on philosophy, neuroscience, and psychology and introduces a new version of concept empiricism called proxytype theory. He also provides accounts of abstract concepts, intentionality, narrow content, and concept combination. In an extended discussion of innateness, he covers Noam Chomsky's arguments for the innateness of grammar, developmental psychologists' arguments for innate cognitive domains, and Jerry Fodor's argument for radical concept nativism.