Reflective Equilibrium, Moral Realism

A reader named jdsm made this comment on my post about reflective equilibrium:

I'm curious as to how you defend your utilitarianism given that you seem to accept ethics itself has serious problems. If your starting intuition is that we all seem to want happiness, that's a far cry from saying happiness is \"good\". It is just saying it is desirable.

jdsm is responding to my comment, recognizing that it's not easy to see why intuitions should be given any weight at all when forming (moral and other) theories. There are a few quick responses that I think are important: (1) I've never tried to "prove" utilitarianism using a universal desire for happiness as a first principle. Those arguments have been made throughout the history of ethics, and are correctly regarded by most as more or less garbage. (2) In my defenses of utilitarianism in my blog, I've been defending the theory against arguments that are based in moral intuition. I have not really been trying to argue against the person who doesn't believe in ethics (or in the use of intuitions in ethics). This is because the comments that got me started on utilitarianism in the first place assumed moral realism. (3) A parallel case will demonstrate that it's not absurd of me to continue thinking in terms of utilitarianism, even though I'm not entirely solid on the basis of moral realism. I believe that there are very old general skeptical concerns that have yet to be answered. Two excellent and famous examples will suffice -- Descartes's argument that we can't know anything about the external world, and Hume's argument that there is no justification for belief in the principle of induction. Both arguments, I think, have never been adequately refuted. But that doesn't mean we shouldn't do physics anyway. Likewise, I believe it is appropriate to work on a moral theory, even if one hasn't yet justified morality in general. If I eventually discover something about morality that is incompatable with what I've been assuming (such as, for example, that it doesn't exist), then obviously I'll take back everything I've said about utilitarianism being true. But I'm not going to wait around until I'm positive that ethics is justifiable before thinking any further, any more than I'd want science to come to a screeching halt until somebody figures out how to justify induction. If it'll make you feel better, think of all my moral theorizing as a giant conditional. "If moral realism is true and something like reflective equilibrium is an appropriate tool for the discovery of moral truths, then I hold the following beliefs and use the following arguments."