Is there a highest good? Aristotle famously thinks so. There is something that is the human thing to do, says he. That thing can be done well or poorly, and the happy person is the one who does it well.
There’s a way of agreeing with Aristotle while missing his point. You might take the highest good to be something like the ultimate justification for action. For anything you do, or anything you do willingly and in good conscience, there is a string of ‘Why?’ questions we could ask you. Why did you tell him the truth? Because you value truth-telling more than convenience. Why do you value truth-telling so? Because it enables honesty and trust among people. Why do you care about those things? Because they make harmonious relationships possible. And so on, until you get to the end of your answers. The last answer you can give, at the end of questions, will be an answer with reference to the highest good: that is simply the human thing to do, the thing that is good for us. This last answer is the final, ultimately justifying reason for doing what you do. The highest good is highest because it is the ultimate reason.
You can think of the same progression in reverse. You want to know what to do in a given situation. Think of the choices available to you, then find the one that is connected to the highest good in a string of reasons for action. The highest good is highest because it is the final justification in your reasons for action.
No doubt, if there is a highest good for human beings, it would make sense to criticize and justify our action with reference to it. But this kind of scenario—reasoning about what to do, or about why you were right to do what you did—is the not the kind of situation in which Aristotle’s notion of the highest good is at home. The reasoning-first understanding of the highest good misses the point because it puts reason in first place. Aristotle’s arguments and doctrines about the good are not (in the first place) about the kind of reasoning we should engage in (although this topic is of course important to him), but about what kind of beings we are. The question What is a correct progression of practical reasoning? is a legitimate question for Aristotle, one that is connected to his idea of the highest good. But the question to ask before that is, What is a human being? The highest good is the highest human good. Only when we understand ourselves will we know how to reason.
