William Lane Craig has given the following argument for years:
[I]f there is no God, then what’s so special about human beings? They’re just accidental by-products of nature which have evolved relatively recently on an infinitesimal speck of dust called the planet Earth, lost somewhere in a hostile and mindless universe, and which are doomed to perish individually and collectively in a relatively short time. On the atheistic view, some action, say, rape, may not be socially advantageous and so in the course of human development has become taboo. But that does absolutely nothing to prove that rape is really morally wrong. On the atheistic view, if you can escape the social consequences, there’s nothing really wrong with your raping someone. And thus without God there is no absolute right and wrong which imposes itself on our conscience.
If find the argument strikingly odd. I really mean what I just said, it’s not code for calling the argument “obviously wrong”. The argument has a sort of dream-like or fairy tale logic to it, like “if you blow out the lamp the kingdom will fall”. The basic insight is that “what is physical” is divided from “what is normative/ moral” in such a way that one cannot derive the one from the other. Very well. But then why is it that moral or normative being needs to be reduced to a divine cause? Why not just say that moral and physical being are different and that’s that? The most striking way to illustrate this might be to turn the argument around: take the normative as a given, insist that one cannot derive physical being from it, and then say that this suffices to prove that God must be the cause of physical being. If this argument is radically defective, why is Craig’s argument any better?
Craig can get away with arguments like this since there is a background premise that everyone is assuming: either naturalism or supernaturalism is true, but our ideas of the natural are so hopeless that Craig is allowed to merely point out something that is different from physical being and immediately conclude that this not only proves the existence of the supernatural, but even that being which is the greatest possible in the supernatural order. But this says far more about the weakness of our account of nature than it does about the power of the moral argument. Craig does have a valuable point, namely that the physical cannot exhaust the real. But this does not prove the existence of God or even make such existence reasonable, it more removes one impediment to the existence of God, namely, the refusal to allow any non-physical reality. Moral experience allows us a way to see that the physical cannot exhaust the real (so does our experience with mathematical things) but one needs to do a great deal more work before this can speak to the fundamental point of disagreement between theism and atheism.
The problem is that given our hopeless understanding of nature, atheists are backed into corners they don’t need to get backed into and theists are left powerless to do anything with the god they think they have found.