Sleep (n.) unbroken from first day to last, for a thousand years, would be no different from the life of a plant.
Sleep (n.) is why for half their lives the good are no better than the bad — though even in sleep, the dreams of the good are better than those of the bad.
Sleep (n.) is a privation of waking — the same organ that lets us perceive is the one that sleeps.
Sleep (n.) belongs neither to pure mind nor to mere bodies: a god does not sleep and neither does a stone.
Sleep (n.) is powerlessness born of too much waking: no creature can keep actualizing its powers forever.
Sleep (n.) is a tie laid on the senses; waking is its loosening.
Sleep (n.) must always be breakable: a sleep from which one could not wake would not be sleep.
Sleep (n.) is not the senses each shutting down, but their master sense being seized — which is why all of them go dark at once.
Sleep (n.) is like epilepsy, and in a sense actually is a seizure of that sort.
Sleep (n.) is heat retreating inward: the eyelids droop as the outer body cools, while the feet and the core stay warm.
Sleep (n.) is Aristotle's model of mere potential: a life asleep from start to finish has life, but no one would call it happy.
Sleep (n.) shows that the happy are no better off than the wretched for half their lives — which is why Aristotle left the nutritive part of the soul out of virtue.