Here is the argument from morality in laid out deductively:
- Objective moral values cannot exist other than in the mind of god
- Objective moral values really do exist (and we all know it)
- :. God exists. QED.
While the argument is valid in form, it is unsound because neither of its premises have been established. The second premise involves an implicit move from “We can all agree that certain actions are never morally justifiable” to “Moral values therefore exist apart from human minds.” How this move (from inter-subjective consensus to non-subjective reality) may be made is never made clear, it is merely assumed that the first premise implies the second. Perhaps there is a rational argument to be made here, but from what I’ve seen, neither W.L. Craig nor C.S. Lewis (who popularized an earlier form of this argument) have ever bothered to do so. It must be noted here that no amount of dramatic hand-waving about horrific atrocities should be considered an argument in support of premise two, however much it stirs the heart.
The first premise is even more troublesome, as it assumes firstly that objective moral values are a coherent concept, and that they must exist (if at all) in the mind of some sort of transcendent being. Here we run into two objections each of which may be avoided by reading one’s Plato. The first is that you become irreversibly impaled upon one of the horns of the Euthyphro dilemma as soon as you assert that moral truths are objectively true in the same sense as mathematical truths, as Craig does. Such an assertion commits you to the view that morality is non-contingent upon the desires and values of any particular deity, however powerful and transcendent it may be, and thereby implies that Craig first premise is necessarily false. In order for that premise to work, “objective moral values” must mean “whatever moral values are subjectively preferred by god” which is sophistry of the highest order.
The second problem with the first premise is that there is not necessarily a logical contradiction to be had in the concept of moral propositions subsisting in something like the Platonic realm of the forms in which ideas exist independently of minds. Skeptics may object that ideas simply cannot exist apart from minds, but this is an objection rooted in induction from everyday experience, not unlike the observation that minds do not exist apart from brains. Once you start arguing in favor of transcendent, timeless and bodiless minds, you forfeit the ability to object based on our own (material and spatiotemporal) experience of how minds and ideas really work for us down here on Earth.