1. Aristotle’s Nicomachean Ethics

2. Eudaimonia Argument Nagel’s Contribution
E1 A thing’s good is determined by that thing’s function (ergon).
E2 The function of x is determined by what x does that nothing else does.
E3 A thing is a good x if (and to the degree that) it performs the function of x well.
E4 Man is the only creature that reasons.
E5 Therefore the function of man is to reason.
C Therefore a thing is a good man if (and to the degree that) it reasons well.
Nagel’s Contribution
In order to reason well, man must live well.

3. Virtue Theory Argument
V1 Man lives well by being a virtuous man (a state of character).
V2 A virtuous man is one who has and exercises the virtues.
V3 Man gets and exercises the virtues by doing what a virtuous man would do in the circumstances.
V4 Therefore one becomes a virtuous man by doing what a virtuous man would do in the circumstances.
C Therefore a man lives well by doing what a virtuous man would do in the circumstances.

4. Modern Virtue Theory Approach
An action is right if it is what a virtuous agent would do in the circumstances.
A virtuous agent is one who acts virtuously—who has and exercises the virtues.
A virtue is a character trait a human needs to flourish or live well (i.e. to reach eudaimonia)