Francis Beckwith's recent post Design, Theism, and Romans 1:20 has elicited a multi-faceted debate taking up, as of this writing, over 130 combox entries. In this post I want to focus on what I see as the most important sub-debate in that thread: that between the "theistic evolutionists" and advocates of intelligent-design theory (ID). Exchanges between Prof. Beckwith and Lydia McGrew afforded most of the substance of that sub-debate. Rather than rehearse its details, however, I shall frame the issue in a way I believe most conducive to progress.
ID presents itself as a scientific theory. It proposes that some features of living things can only be explained as products of intelligent design, and its proponents are confident that such a proposition is scientifically testable. For two reasons, though, I am not concerned with the question whether such confidence is justified. For one thing, I am not qualified to judge. But more important, I believe that the overarching philosophical question at stake would be left largely untouched even if ID were empirically well-confirmed.
I say "largely" but not "wholly" because the success of ID, if that were forthcoming, would at least be philosophically relevant. By showing that neo-Darwinism is scientifically inadequate as an explanation for the development of species, it would rightly cast doubt on the thesis of neo-Darwinian materialists that the origin of life itself can eventually be explained in non-teleological terms. And the ranks of those finding support for classical theism in ID would certainly be bolstered. But I do not share the confidence of ID theorists that things will take such a happy course; and even if they did, materialist neo-Darwinians could always emulate the old defenders of geocentrism by having recourse to epicyclical explanations for which they could claim predictive value. They could, that is, postulate that the pertinent features were designed by other material, if admittedly intelligent, beings. I have read that Richard Dawkins has already armed himself with such a comeback on the off chance that it turns out to be needed. Although it's hard to see how that postulate could be tested, it would in principle be testable.
But those aren't even the main reasons I disbelieve that ID can offer what most of its proponents seem to want: scientific evidence for classical theism. As I implied in my review of Georgetown theologian John Haught's book Is Nature Enough? Truth and Meaning in the Age of Science (2006), the very idea of seeking scientific evidence for classical theism is a category mistake. The aims, methods, and canons of natural science, though not immune to revision, remain just as they are whether or not classical theism is true. There is no scientific work for an appeal to a "God of the gaps" to do.
A more promising tack, I believe, would be to show that natural science does not, because it cannot, answer a certain question that its results make it reasonable to raise: why are the laws of nature, whatever they are, what they are? Natural science entails discovering causal regularities and subsuming them under higher-order causal regularities. Those are what natural science uses to explain and predict observable events. Within its proper sphere, it does so quite successfully; it might conceivably come up with a confirmable "Theory of Everything," where the quantifier ranges over physical things. And the nested set of causal regularities such a theory would present would just be "the laws of nature." But that doesn't rule out the question why the-totality-of-things-that-change, or what Wittgenstain termed "the sphere of what happens," exists.
Call that totality 'T'. Granted we do not know its full extent, and may never know it short of the Eschaton, T certainly exists. The question why T exists is meaningful because we cannot rule out that T embodies the intention of something it does not comprise, and is in that sense telic. We could rule out that possibility, and thus render the question meaningless, only by premising scientism: the thesis that only what can be known by means of modern science, and thus without recourse to final (and formal) causes, can be known at all. Yet, for reasons that needn't be explained, no scientific argument for scientism can be given. Scientism is a philosophical option for which, I've suggested, the arguments are essentially moral arguments. Given the full range and depth of human experience, those arguments are not particularly persuasive. And once one realizes that the question why T exists admits only a teleological answer if it is answerable at all, then a successful ID could be taken as evidence that the question is quite reasonable to raise. A true and non-trivial answer to that question would also afford an answer to the question why the laws of nature are as they are.
A successful ID would not and could not provide the answer to either question; but it would provide a good reason to admit both—a better reason, I should think, then Dawkins' saving-the-appearances hypothesis would be for excluding them. Here, "theistic evolutionists" would be on terra firma they could share with ID theorists. But only if ID proves itself scientifically cogent.