"On the Soul" is a philosophical treatise written by Aristotle in the 4th century BC. The book is focused on the nature of the soul and its relationship to the body, as well as the various faculties of the soul such as perception, thought, and desire. The majority of the book is devoted to the discussion of the various faculties of the soul. Aristotle examines perception, memory, imagination, and thought in detail, and argues that these faculties are interconnected and form a hierarchy of cognitive processes. He also discusses the role of desire in human behavior, and how it relates to the other faculties of the soul. Read in English, unabridged.