This work is designed to make Aristotle's neglected but fascinating writings on sleep and dreams accessible in translation to modern readers, and to provide a commentary with a contemporary perspective. It considers Aristotle's theory of dreams in historical context, especially in relation to Plato. It also discusses neo-Freudian interpretations of Aristotle and contemporary experimental psychology of dreaming. Aristotle's account of dreaming as a function of the imagination is examined from a philosophical perspective. The work is revised and corrected version of the North American edition.