The version of the design argument on which Paley rests his case begins with certain features of organisms. Other versions start from the observation, in Hume’s phrase, that the entire universe is “one great machine, subdivided into an infinite number of lesser machines.” And one of these other versions has received a great deal of attention in the recent philosophical literature: the so-called fine-tuning argument. The fine-tuning argument is also in Natural Theology, although Paley is not usually credited in contemporary discussions. There are, Paley says, an “infinite number of possible laws” that could have governed material objects (in particular, the heavenly bodies), and out of “a boundless variety of suppositions which were equally possible,” and despite “a thousand chances against conveniency,” the laws that do in fact obtain are “beneficial.” The universe, in other words, is fine-tuned for life. The remarkable fact that the universe is so hospitable needs an explanation, and isn’t the hypothesis of a designer the best one?
One might object that explanation has to stop somewhere. The eye is not a credible candidate for a stopping point, but perhaps the basic physical laws are the sorts of things that have no explanation. If so, the fine-tuning argument does not get started. But let us (perhaps generously) admit that an explanation is required: why, we may ask, is the universe apparently made for life?
The fine-tuning argument did not appear in Darwin’s Black Box, but it has a starring role in Behe’s latest book, The Edge of Evolution. One of the most extensive discussions of the argument in the philosophical literature is John Leslie’s Universes, and—as the title hints—a rival explanation of fine-tuning is that our universe is only one of many universes, just as our sun is a single twinkle in the sidereal plenitude. If universes exist in “boundless variety,” each with a distinct set of basic physical laws, then the fact that the laws of our universe are “beneficial” would seem to be nothing to get excited about.
This “multiverse hypothesis” stands to the fine-tuning argument for God’s existence as Darwinism stands to Paley’s biological design argument: it is an alternative “no-design” explanation of the data. If the fundamental organizing principle of modern biology is pitted against a rival hypothesis that receives no serious consideration in professional journals, the outcome is not in doubt. But if the alternative to design is cosmological speculation (by philosophers, no less!), the contest looks to be back on a much more equal footing.
Dawkins, then, makes a significant concession when he turns in The God Delusion to the fine-tuning argument. He replies in exactly the same way he does to Paley, by arguing that the multiverse hypothesis should be preferred over the “God hypothesis,” because the former is considerably more “simple.” Well, maybe—but unlike the Darwinian reply to Paley’s argument, this point is eminently debatable. And in any case, the idea that the multiverse hypothesis could provide any kind of explanation of why our universe is fine-tuned is controversial.
Hume suggests a more convincing rebuttal. His two objections apply equally well to the fine-tuning argument for the existence of God. First, the fine-tuning argument is silent on the number and attributes of any designers. Further, it is quite unclear what the designer or designers could be like, which contrasts the fine-tuning argument unfavorably with the biological design argument. At least we may intelligibly hypothesize about the designers of the eye—perhaps a race of extraterrestrials visited the earth about half a billion years ago to manufacture the early prototypes. But if any sense can be made of agents creating the totality of space-time, it cannot be by comparison with familiar artisans like watchmakers, quilters, and pastry chefs, who do their work at particular times and places according to ordinary causal laws.
Hume’s second objection is that there is no reason to favor the (unspecific, and perhaps not even intelligible) design hypothesis over the (also unspecific) hypothesis that fine-tuning can be explained in some other way. How could we be in a position to rule out all the no-design alternatives? Hume sketchees a number of possibilities (including an ancient version of the multiverse hypothesis), of which perhaps the most interesting compares the structure of the universe to structures found in mathematics. The explanation of arithmetical structure, as any “skilful algebraist” will tell you, is not to be found either in “chance or design,” or the hypothesis of a multiplicity of other structures, but instead in the “nature of . . . numbers.” Likewise, perhaps “the whole economy of the universe is conducted by a like necessity, though no human algebra can furnish a key, which solves the difficulty.”
And I think Alex Byrne ends his article quite appropriately:
If a persuasive argument for the existence of God is wanted, then philosophy has come up empty. The traditional arguments have much to teach us, but concentrating on them can disguise a simple but important point. As Anselm and Paley both recognized, the devout are not exactly holding their collective breath. For the most part, they do not believe that God exists on the basis of any argument. How they know that God exists, if they do, is itself unknown—the devout do not know that God exists in the way it is known that dinosaurs existed, or that there exist infinitely many prime numbers. The funny thing about arguments for the existence of God is that, if they succeed, they were never needed in the first place.
Read the full article here.