Stephen Everson presents a comprehensive new study of Aristotle's account of perception and related mental capacities. Recent debate about Aristotle's theory of mind has focused on this account, which is Aristotle's most sustained and detailed attempt to describe and explain the behaviour of living things. Everson places it in the context of Aristotle's natural science as a whole, showing how he applies the explanatory tools developed in other works to the study of perceptual cognition. Everson demonstrates that, contrary to the claims of many recent scholars, Aristotle is indeed concerned to explain perceptual activity as the activity of a living body, in terms of material changes in the organs which possess the various perceptual capacities. By emphasizing the unified nature of the perceptual system, Everson is able to explain how Aristotle accounts for our ability to perceive not only such things as colours and sounds but material objects in our environment.This rich and broad-ranging book will be essential reading not only for students of Aristotle's theory of mind but for all those concerned to understand the explanatory principles of his natural science.