Kyle Cupp at Vox Nova was critical of an argument by Peter Kreeft that God is the foundation of the moral law. Part of Kyle’s critique involves playing down the fact that Kreeft is not making a moral argument but a cosmological argument, but there are still interesting questions that arise around the argument in question.
1.) Kreeft appeals to the moral law as unchangeable and eternal, but it is questionable if St. Thomas would call moral laws eternal in a meaningful way (i.e. beyond the sense that everything is eternal in the mind of God, if it’s given God exists). It is hard to see why the moral laws we know would be any more eternal than the Pythagorean theorem that we know, and in Thomistic theory, the latter is not eternal nor immutable. As the objections in the articles linked to make clear, this is a point of dispute between Thomas and Augustine. Gilson does a particularly impressive job making a harmony between the two accounts in Chapter V of his Christian Philosophy of St. Augustine (esp. pp 68 and following.).
2.) The idea of a “basis” or “foundation” or “source” of morality seems to be an effect of morality conceived of as obligation or law, followed by the idea that any mutable, contingent laws must participate in an immutable one (in this sense, Kreeft’s argument is just a concrete application of the ideas used in cosmological arguments, bolstered by the fact that we [i.e. Anglophones in the contemporary world] seem to have an easier time perceiving the dependence that mutable or variable laws have on unchanging one, or the dependence of positive law/right on natural law/right) St. Thomas, on the other hand, viewed the source of morality as the ultimate goal or end or action, and he gave arguments for why only the creator could be such a goal. This makes for a very different sort of theistic argument from moral facts, one where God becomes the foundation of morality because he is the goal of human life.
3.) It’s interesting that Kreeft (or Craig, who gives a similar argument) does not appeal to conscience, as Newman did when he gave much the same argument. Even as recently as Gaudium et Spes this sort of argument would have made conscience basic and fundamental. I wonder if we’ve grown wary of appeals to conscience.