In Book I of his Nicomachean Ethics (NE), Aristotle defines happiness, or eudaimonia, in accordance with an argument he makes regarding the distinctive function of human beings. In this paper, I argue that, despite this argument, there are moments in the NE where Aristotle appeals to elements of happiness that don’t follow from the function argument itself. The place of these elements in Aristotle’s account of happiness should, therefore, be a matter of perplexity. For, how can Aristotle appeal to elements (...) of happiness not entailed by his argument for what happiness involves? I will examine two instances that exemplify the sort of appeal to outside elements that I have in mind. The first deals with Aristotle’s reference, in NE, I, 8, to certain goods—ancestry, children, beauty—goods unrelated to man’s function or his fulfillment of it, but nevertheless required for his happiness. The second instance involves pleasure. Aristotle makes various arguments, both in Books I and X of the NE, that tie pleasure to the activity of the soul, and the function argument in turn. However, none of these arguments succeeds in demonstrating that pleasure would necessarily follow from this activity. Taken together then, these two examples demonstrate the extent to which Aristotle’s definition of happiness is more inclusive than his function argument permits. (shrink)