Aristotle’s answer to, “Is not all slavery a violation of nature?”

From POLITICS by Aristotle, 350 BC:

There is no difficulty in answering this question, on grounds both of reason and of fact. … For that some should rule and others be ruled is a thing not only necessary, but expedient; from the hour of their birth, some are marked out for subjection, others for rule. … Again, the male is by nature superior, and the female inferior; and the one rules, and the other is ruled; this principle, of necessity, extends to all mankind. … It is clear, then, that some men are by nature free, and others slaves, and that for these latter slavery is both expedient and right.