The passage I will discuss in this paper, one of the best known in the Aristotelian corpus, occurs in Book I chapter 7 of the Nicomachean Ethics, and concerns the ergon, i.e. the function, of human beings. Aristotle argues that we have a function, that our happiness consists in fulfilling it, and that this function must be idion, i.e. it must be peculiar to us. On this basis, he asserts that our function cannot consist in being alive, nourishment, growth, or perception, for these activities are common to other species. Aristotle then arrives at his familiar conclusion that our function consists in the excellent use of reason.