Aristotle, Physics Book II (Ch 1-3); Book III (Ch 1-3; 6-9)

Now exactly in the same way the body, which like the axe is an instrument – for both the body as a whole and its several parts individually have definite operations for which they are made – just in the same way, I say, the body, if it is to do its work, must of necessity be of such and such a character, and made of such and such materials. ................
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