Present-day behavioral and cognitive neuroscience is based on the idea that the conventional philosophical theory of the mind provides a reliable guide to the functional organization of the brain. Consequently, much effort has been expended in a search for the neural basis of such psychological categories as memory, attention, emotion, motivation, and perception. This book argues that (a) conventional psychological concepts originate from the philosophical speculations of ancient Greek philosophers, especially Plato and Aristotle; (b) there is serious doubt that these ancient philosophical analyses provide a reliable guide to the understanding of the human mind, human behavior, or the organization of the brain; and (c) that modern scientific studies of animal behavior provide a better guide to the study of the functional organization of the brain than is provided by conventional psychological concepts.