The key to understanding Aristotle’s view is that the aim is included in the description of the action, and that it is the action as a whole, including the aim, that the agent chooses.
Let us say that out agent is a citizen-soldier, who chooses to sacrifice his life for the sake of a victory for his polis or city. The Greeks seem to think that is usually a good aim. Let’s also assume that our soldier sacrifices himself at the right time — not before it is necessary, perhaps, or when something especially good, say cutting off the enemy’s access to reinforcements, may be achieved by it. And he does it in the right way, efficiently and unflinchingly, perhaps even with style, and so on. Then he has done something courageous, a good action. Why has he done it? His purpose is to secure a victory for his city. But the object of his choice is the whole action — sacrificing his life in a certain way at a certain time in order to secure a victory for the city. He chooses this whole package, that is, to-do-this-act-for-the-sake-of-this-end — he chooses that, the whole package, as a thing worth doing for its own sake, and without any further end. “Noble” describes the kind of value that the whole package has, the value that he sees in it when he chooses it.
(Korsgaard, Self-Constitution: 10)
1. I am not entirely sure this metaphysics of action can help rationalize the claim that good actions are actions for their own sake (ibid: 9). Consider the following analogy: Suppose Jon wants to have a X because X has O as a part (e.g., a shiny surface). Actually, anything that has O as a part would do for Jon. But X happens to be around and he wants X for that. In this case, although O is part of X, Jon’s desire for X in virtue of O is not a case of Jon desiring X for its own sake, I presume. So, Korsgaard’s claim that the purpose of an action is a part of that action cannot help vindicate the claim that good actions are actions for their own sake.
2. Korsgaard’s account might overkill. If she is right, why aren’t all intentional actions actions for their own sake? Why the good actions alone?