I know twenty or thirty people who, given the chance, could come up with a vastly improved Aristotle. I count myself among this group, and if we had ever formed a committee to do the job, I know the assignment I would have wanted: inserting texts in which Aristotle says that as a given thing can survive without a certain characteristic, the characteristic is not essential to the thing.

Aristotle does, from time to time, invoke the survivability criterion, or what amounts to the same thing – most typically, in claiming that living things and their parts are essentially animate. And in the Metaphysics VII, 15, he criticizes those who would define the sun as “going round the earth”: “they err … by adding attributes after whose removal the sun would still exist.” On their view, if the sun were to stand still, it would no longer be the sun – a strange consequence, “for ‘the sun’ means a certain substance” [1040a28–33]. Outside of a biological context this sort of statement is rare, and at crucial junctures where a quick invocation of the survivability criterion would seem appropriate, Aristotle refrains.

In Metaphysics VII, 4, he addresses the question of whether an essence corresponds to “pale man” by asking whether “pale man” involves one thing's being said of another. How much easier it would have been to point out that, if the pale man spends some time in the sun, he will tan: that paleness is an attribute loss of which people survive each summer.