I think that what this objection is really getting at is the claim that it’s somehow arbitrary to adopt God’s nature as the Good. But every moral realist theory has to have an explanatory stopping point at which one reaches the ultimate good. Anyone who broaches a moral theory is entitled to identify whatever he wants as his ultimate explanatory stopping point. The question, then, will be, is the explanatory ultimate posited by some moral theory plausible? In the case of theism, taking God to be one’s explanatory ultimate is, I think, eminently plausible. For the very concept of God is the concept of a necessary, metaphysically ultimate being, one, moreover, that is worthy of worship. Indeed, He is the greatest conceivable being , and it is greater to be the Good than merely to reflect it. So the theist’s stopping point, in contrast to, say, the humanist’s, is not at all arbitrary or premature.