The problems are twofold. First, both Paleyan “design arguments” and ID theory take for granted an essentially mechanistic conception of the natural world. What this means is that they deny the existence of the sort of immanent teleology or final causality affirmed by the Aristotelian-Thomistic-Scholastic tradition, and instead regard all teleology as imposed, “artificially” as it were, from outside. I devoted a couple of recent posts to explaining in some detail the differences between these approaches to teleology (here and here). And I emphasized that one of the objections the Aristotelian-Thomistic (A-T) tradition has to the mechanistic denial of final causality is that it makes efficient causality unintelligible. Causes and effects become “loose and separate”; any effect or none might in principle follow upon any cause. This not only paves the way for the paradoxes of Hume, but (more to the present point) undermines the possibility of showing how the very fact of causation as such presupposes a sustaining First Uncaused Cause. The metaphysically necessary connection between the world and God is broken; in principle the world could exist and operate just as it does apart from God. The most we can say is that this is so improbable a hypothesis that it can safely be ruled out; for as Paley and Co. assure us, it is far more likely that an extremely powerful and intelligent “designer” put together the “machine” that is the universe.
The second problem is that Paley and Co. conceptualize this designer on the model of human tinkerers, attributing our characteristics (intelligence, power, etc.) to him in a univocal rather than an analogous way (to allude to a crucial Thomistic distinction explained in a previous post). To be sure, “design arguments” also emphasize that the differences between human artifacts and the universe indicate that the designer’s power and intelligence must be far vaster than ours. But we are necessarily left with a designer conceived of in anthropomorphic terms – essentially a human being, or at least a Cartesian immaterial substance, with the limitations abstracted away. The result is the “theistic personalism” (as Brian Davies has labeled it) which has displaced classical theism in the thinking of many contemporary philosophers of religion.
“OK,” you might say, “so the arguments in question do not get us with certainty all the way to the God of classical theism. So they only get us part way, and only with probability. That’s something, isn’t it?”
Well, no, actually it isn’t. Suppose you are a Christian, and suppose I gave you a powerful argument for the existence of Zeus, or of Quetzalcoatl. Would you run out and wave it defiantly in the faces of your New Atheist friends? Presumably not; it would be less a vindication than an embarrassment. To be sure, such an argument wouldn’t necessarily be incompatible with Christianity. You could always interpret Zeus or Quetzalcoatl as merely an unusually impressive created being – a demon, say, or an extraterrestrial. Indeed, that’s how you should interpret them if they are real, because whatever Zeus or Quetzalcoatl would be if they existed, they would not be divine in the classical theistic sense of “divine.” On classical theism, there doesn’t simply happen to be one God, as if only one applicant bothered responding to the "Creator needed; long hours but good benefits" job ad; there couldn’t possibly be more than one God, given what God is. Anything less than Being Itself or Pure Act, anything less than That Than Which No Greater Can Be Conceived, anything less than that which is absolute divine simplicity, absolutely incomparable, would simply not be God. There is no such thing as “almost” being God; it’s all or nothing. But precisely for that reason, while to prove the existence of Zeus or Quetzalcoatl would not be to disprove God’s existence, neither would it advance you one inch to proving it. It would be completely irrelevant.
Same thing with the arguments of Paley and Co. You do not get from them – not one inch, not one degree of probability – to the God of classical theism, of Athanasius, Augustine, Anselm, and Aquinas, of the Creeds and councils of the Church, the “I am who am” of Exodus. What you get instead is something like the Ralph Richardson Supreme Being character from Time Bandits. Really really powerful? – no doubt about it. Super smart too – wouldn’t want to play Trivial Pursuit against him! A snappy dresser. But not God. Because a god apart from whom the world might in theory exist anyway – as a mechanical conception of nature entails – is not, cannot be, the God of classical theism. Nor can a god who is powerful and intelligent in just the way we are, only more so.
Or as the analytical Thomist philosopher Christopher F. J. Martin amusingly puts it in his very fine book Thomas Aquinas: God and Explanations:
The Being whose existence is revealed to us by the argument from design is not God but the Great Architect of the Deists and Freemasons, an impostor disguised as God, a stern, kindly, and immensely clever old English gentleman, equipped with apron, trowel, square and compasses. Blake has a famous picture of this figure to be seen on the walls of a thousand student bedrooms during the nineteen-seventies: the strong wind which is apparently blowing in the picture has blown away the apron, trowel and set-square but left him his beard and compasses. Ironies of history have meant that this picture of Blake’s is often taken to be a picture of God the Creator, while in fact Blake drew it as a picture of Urizen, a being who shares some of the attributes of the Great Architect and some of those of Satan.
The Great Architect is not God because he is just someone like us but a lot older, cleverer and more skilful. He decides what he wants to do and therefore sets about doing the things he needs to do to achieve it. God is not like that. As Hobbes memorably said, "God hath no ends": there is nothing that God is up to, nothing he needs to get done, nothing he needs to do to get things done. In no less lapidary Latin, Aquinas said "Vult ergo Deus hoc esse propter hoc; sed non propter hoc vult hoc". In definitely unlapidary English we could say: The set-up, A-for-the-sake-of-B is something that God wants; but it is not that God wants B and for that reason wants A. We know that the set-up A-for-the-sake-of-B is something that God wants, because it is something that exists, and everything that exists, exists because of God’s will. But it is simply profane to think that you can infer from that the unfathomable secrets of the inside of God’s mind and will. Acorns for the sake of oak trees, to repeat an example of Geach’s, are definitely something that God wants, since that is the way things are. But it is not that God has any special desire for oak trees (as the Great Architect might), and for that reason finds himself obliged to fiddle about with acorns. If God wants oak-trees, he can have them, zap! You want oak trees, you got ’em. "Let there be oak trees", by inference, is one of the things said on the third day of creation, and oak trees are made. There is no suggestion that acorns have to come first: indeed, the suggestion is quite the other way around. To "which came first, the acorn or the oak?" it looks as if the answer is quite definitely "the oak". In any case, what’s so special about oak trees that God should have to fiddle around with acorns to make them? God is mysterious: the whole objection to the great architect is that we know him all too well, since he is one of us. Whatever God is, God is not one of us: a sobering thought for those who use "one of us" as their highest term of approbation.
The argument from design fails, then, because [as Martin argues earlier in the book] it is an argument from ignorance, because it confuses the final and efficient modes of explanation, and because even if it succeeded it would not prove the existence of God but of some Masonic impostor. But like other bad arguments, its defeat and death has left it to wander the world like a ghost, oppressing the spirits of those who are looking for other and better arguments. (pp. 181-2)
Needless to say, to worship Urizen or Ralph Richardson is not to worship God. But then, to devote enormous amounts of energy to defending arguments which could only ever get you to Urizen or Ralph Richardson would seem an odd enterprise for those whose interest is in promoting the worship of God. This is part of the problem with Paley-style “design arguments” and ID theory, at least insofar as the latter is thought to give support to theism. Even if they are successful – and my own view is that they are at least better than Martin gives them credit for – they distract attention from arguments which really do establish the existence of God. Worse, they lead people to a false conception of God – God as an anthropomorphic tinkerer, God as a cosmic Boy Scout or Santa Claus, a god-of-the-gaps, a scientific posit on all fours with quarks and selective pressures.
“But ID arguments raise serious questions about Darwinism!” Maybe so, and that is not unimportant. But my interest here is in the question of what sorts of arguments establish the existence of the God of classical theism. And to challenge Darwinism, even to refute Darwinism, would not be to establish classical theism. Indeed, it would not even be to refute naturalism. For, the pretenses of its less astute advocates notwithstanding, naturalism is a metaphysical theory, not an empirical one; and it is always possible for a naturalist to throw up his hands at Darwinism’s failure to explain this or that, and insist on general metaphysical grounds that there must nevertheless be some other naturalistic explanation or other out there, even if we have not or cannot discover it. That is in effect the approach taken by wiser naturalists – not Darwinian religious fanatics like Dawkins, Dennett, and Co., but more sober and serious theorists like David Stove, Jerry Fodor, Thomas Nagel, and Noam Chomsky, none of whom thinks Darwinism has come anywhere close to a complete naturalistic explanation of biological phenomena.
That is not to say that I think naturalistic metaphysics is believable even for a moment. It isn’t. But the point is that the dispute concerns basic metaphysics, not empirical science. Where the dispute over theism, specifically, is concerned, it is a waste of time to try to beat the naturalists at their own game, viz. empirical theorizing on the basis of a mechanistic conception of nature. That sort of thing will only ever get you at best to very remote, unusual, even extremely unexpected and impressive – but still perfectly natural – phenomena. It will not get you in the slightest toward God, because God is not one natural object among others, not even the most powerful and intelligent natural object, not even an immaterial natural object. (From a Scholastic point of view, “natural” does not entail “material” – angels and demons are immaterial, but still part of the natural, created order. Nor does the entailment seem to hold even from a naturalistic point of view, given e.g. that Quine is perfectly happy to countenance abstract objects if they are necessary to make sense of empirical science.)
The trouble with Paley-style arguments, then, is not that they are bad science – they may or may not be, depending on which ones we are talking about – but that they are bad theology. If you assume otherwise, then perhaps – as J. B. Phillips put it in a different context – your god is too small.