On Dreams (Ancient Greek: Περὶ ἐνυπνίων; Latin: De insomniis) is one of the short treatises that make up Aristotle's Parva Naturalia. The short text is divided into three chapters. In the first, Aristotle tries to determine whether dreams "pertain to the faculty of thought or to that of sense-perception." In the second chapter, he considers the circumstances of sleep and how the sense organs operate. Finally, in the third chapter he explains how dreams are caused, proposing that it is the residual movements of the sensory organs that allow them to arise.