Elliot, right, the best defense for categorical normativity is theism, but I guess I’m going to disagree with you there: I think that, the efforts of countless theologians notwithstanding, Plato really did nail that one. There is no way out of the Euthyphro dilemma. And if that were not enough, I am certainly no theist. So, again, ethical naturalism is the only viable option I can see.