 One worry about this argument is that it might overgeneralize. The “because” structure seems to be shared by other normative domains: it would be very odd to claim that a particular chess move was winning, or that a particular action was illegal, without being committed to their being some general explanation in terms of the rules of chess, or the relevant laws, that explains this particular fact. But our knowledge of the law and the rules of chess is empirical. So one might wonder what precisely prevents our knowledge of ethical principles being empirical as well.