Another Problem With the Moral Argument: Moral reductions and mental reductions

When I tell theists that I am both an atheist and a moral realist, the most common response is "How do you ground morality?" Over time I've realized this question is a very poor one for a number of reasons, but maybe the most interesting is that any argument one might abstract from it would actually hurt theism. The idea, supposedly, is that atheists cannot ground morality (or draw a metaphysical reduction) in anything within their ontology, but theists can. And so by comparing how the two world views are able to handle the existence of moral entities and given the assumption that there are in fact moral entities, the theist thinks that his world view comes out on top. Immediately one might wonder, why must moral entities be grounded in anything anyway? Why can't they simply be what we conceive them to be, why must there be more to the picture? In other words, why is it that to rationally believe in the existence of objective right and wrong, we must be able to identify something within our ontology that rightness and wrongness are non-trivially identical to? The only answer I've ever heard is that moral entities are just metaphysically queer, and so unless we can identify them with something that isn't so strange, we ought to reject their existence. I have serious doubts about this answer: whatever metaphysical queerness there is in moral entities, it must be just intrinsically a part of the concept of morality or else we could easily strip off the queer parts and keep the rest. And indeed I think this is the case; typically it's the objective normativity that is considered metaphysically queer, and to strip that from morality would seem to destroy the concept of morality entirely. Yet if whatever we reduced moral entities to had the same queerness about it (e.g. was also objectively normative), then that would simply call for further grounding. And so either the grounding doesn't actually explain anything interesting, or it's simply not needed (as we can just strip away the queerness without the reduction), or it destroys morality (since the queerness was an essential part that is now lost by the reduction).

Nevertheless, let's just suppose that a rational person will either find something to ground morality in, or reject morality all together. This does not bode well for theism. Why? Because there are other things that the theist might want to believe in that have an air of queerness about them or intuitively call for grounding, like minds. And what is our currently best reductionist theory of mental states? It is that mental states reduce in some way to brain states. And so if the theist is going to charge the atheist with ignoring our currently best reduction of obligations to divine commands (supposing that is, in fact, the best current theory), then the atheist can just as easily retort that the theist is ignoring our currently best reduction of minds to brains. But if the theist were to even entertain this reductive theory of minds, he would have a very serious problem on his hands. God is, after all, an unembodied mind and thus on this theory would be impossible.

Now maybe there's some grounding principle the theist could come up with that is both plausible enough, and only calls for the grounding of morality and not for the grounding of minds, but I can't see what that could possibly be. Until the theist is able to flesh out such a principle, though, the question of "How do you ground objective morality?" will ultimately bite them back with even more force.