On Dreams
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. Content Aristotle explains that during sleep there is an absence of external sensory stimulation. While sleeping with our eyes closed, the eyes are unable to see, and so in this respect we perceive nothing while asleep. He compares hallucinations to dreams, saying "...the faculty by which, in waking hours, we are subject to illusion when affected by disease, is identical with that which produces illusory effects in sleep." When awake and perceiving, to see or hear something incorrectly only occurs when one actually sees or hears something, thinking it to be something else. But in sleep, if it is still true that one does not see, hear, or