Aristotle’s Theory of Sleep Viewed by Modern Science
Aristotle was the first philosopher in the Western tradition to develop a comprehensive scientific theory of sleep, outlined in his treatise On Sleep and Wakefulness. Contrary to the opinion of most popularisers and historians of science, his theory was neither naïve nor erroneous but brilliantly anticipated some modern ideas about the essence, causes, and purpose of sleep. This paper takes a close look at the text of Aristotle’s treatise to compare his views on formal, final, material, and efficient causes of sleep with the latest findings of modern somnology. The paper shows that the ancient philosopher was able to answer many questions that remain unresolved in the current sleep research. Aristotle defined the essence and purpose of sleep, established its difference from other unconscious states of the animal, predicted the presence of sleep in all species of animals and proved the necessity of sleep for their survival. Moreover, he correctly described the anatomy and physiology of sleep, discovering the existence of a single source of sleep-wake states, dividing sleep into different phases, and revealing the self-regulating sleep mechanism associated with metabolic processes constantly occurring in the body.