In the Nicomachean Ethics, Aristotle appears to use an elegant short argument to attack Plato's doctrine of the good, which argument equally appears to attack Aristotle's own doctrine of the good. I consider these two questions: First: Why does Aristotle reverse the judgment of Socrates/Plato on the issue: Which is better - things that are good in themselves, or things that are both good in themselves and good for their consequences? Second: Why does Aristotle attack Plato's doctrine that the Form (...) of the Good is the chief good, with an argument that appears to threaten his own view that eudaimonia is the chief good? I think the answers to these two questions are related. The elegant short argument in question I call "Aristotle's Fast Argument." After apologizing for criticizing views held by friends of his, Aristotle deploys the Fast Argument as a clincher to cap off his refutation of Plato's view that the Form of the Good is the chief good: "And one might ask the question, what in the world they mean by 'a thing itself', if in man himself and in a particular man the account of man is one and the same. For in so far as they are men, they will in no respect differ; and if this is so, neither will there be a difference in so far as they are good. But again it will not be good any the more for being eternal, since that which lasts long is no whiter than that which perishes in a day.". I explore this sketchily presented Fast Argument. I consider why Aristotle may think it is valid and why he does not seem to realize that, on readings that make it effective against Plato's view, his Fast Argument also seems to apply to his own view that eudaimonia is the chief good. This is what I will call "Aristotle's Dilemma." If the Fast Argument is interpreted too narrowly, its point about the whiteness of a white thing being independent of its duration will not apply to the goodness of the Form of the Good. If it is interpreted broadly enough to undermine the claim of the Form of the Good to be the chief good, it will equally undermine that claim for eudaimonia. Finally, I discuss some of the things Plato and Aristotle say about the chief good, and comparable things Immanuel Kant says about the good will. I draw some speculative conclusions that focus on the importance for Aristotle of the goodness of the chief good not being at risk. (shrink)