Why We Sleep?

This paper focuses on Pre-Aristotelian theories of sleep. Greek thinkers proposed various physical explanations of sleep, overall portraying sleeping as a form of cooling. According to the evidence available, most of them did not connect sleep with a state of fatigue and the resulting need of rest for the body. I examine the extent to which Pre-Aristotelian thinkers accounted for the restorative function of sleep, thus picturing sleep as a vital biological process for living things.