 The paradigmatic strategy for deriving ethical consequences from claims about structural features of the human life form is the Platonic and Aristotelian ergon or function argument. The first premise of Aristotle’s version (Nicomachean Ethics 1097b–1098a) connects function and goodness: if the characteristic function of an entity of a type X is to φ, then a good entity of type X is one that φs well. Aristotle confers plausibility on the claim by using examples such as social roles and bodily organs. If the function of an eye as an exemplar of its kind is to enable seeing, then a good eye is one that enables its bearer to see well. The second premise of the argument is a claim we encountered in  section 1.4  of this entry, a claim we can now see as predicating a structural property of human life, the exercise of reason. According to this claim, the function or end of individual humans as humans is, depending on interpretation (Nussbaum 1995: 113ff.), either the exercise of reason or life according to reason. If this is correct, it follows that a good human being is one whose life centrally involves the exercise of, or life in accordance with, reason.