Physicist Stephen M. Barr has fired the latest broadside in the contentious debate over what science tells us about the existence of God. His book Modern Physics and Ancient Faith presents a case that developments in physics and related fields give support to the idea of a cosmic designer and indeed fit well with the Judeo-Christian tradition.

I have long followed the science-and-religion debate, and have been quite critical of arguments similar to Barr's. In particular, a 1999 article of mine in Reason magazine looked skeptically at claims that the laws of physics are "fine tuned" for human existence. More recently, at TCS, I gave a generally favorable review to physicist Victor Stenger's skeptical book Has Science Found God? (I disagreed, however, with Stenger's view that science provides strong grounds for atheism.)

Modern Physics and Ancient Faith (University of Notre Dame Press) is the most impressive statement I have seen of the thesis that science has found indications of the divine. Barr, a professor of physics at the University of Delaware's Bartol Research Institute, presents a thought-provoking discussion that ranges across physics, cosmology and mathematics. He refrains from overblown claims of proof, instead asserting that scientific advances of the past century comport better with the expectations of religious believers than with those of scientific materialists. Barr also shows a willingness to grapple with skeptics' objections. The book can be read profitably for its discussions of various scientific topics, leaving aside whether one agrees with the overall argument.

That argument, however, has serious flaws and limitations. For one thing, Barr sees evidence of design in the mathematical symmetries that physicists increasingly have discerned in the laws of nature. The special theory of relativity, for example, involves "space-time rotation symmetry," meaning the laws of physics and the speed of light look the same to all observers. But such symmetries arise from simplicity and indeed are seen by some physicists (such as Stenger) as signifying a lack of design. A universe that contained nothing but empty space would have perfect "space rotation symmetry" and "time translation symmetry." Would that empty universe be indicative of design?

Barr also asserts, as do many physicists, that the laws of physics are "beautiful." And such beauty, he writes, suggests "the mind of an artist at work that is far above the level of our own minds." Yet some scientists, such as astrophysicist Mario Livio, perceive at least some of the beauty of physical laws as arising precisely from their indifference to human affairs and lack of contrivance, the opposite of Barr's emphasis. My layman's opinion is that beauty in physics is in the eye of the physicist beholder.

Central to Barr's argument is the apparent "fine tuning" of the laws of physics. Various physical parameters, such as the strength of the electromagnetic force or the mass of the proton, seem to be set at just the right levels to allow life to exist. If they were different, we wouldn't be here. Does this mean that the universe was created for us? There are numerous problems with reaching such a conclusion. For one thing, the parameters seem to be just right for life as we know it; it could be that other types of universes would be suitable for other types of life. Moreover, it is hard to get an intelligent sense of what the universe would be like with different parameters. What if one changes not only electromagnetism but also gravity and other forces? Short answer: Who knows?

Many physicists speculate that there exist multiple universes (or multiple regions of our own universe) across which the parameters vary. This, in fact, is a common counterargument to the notion of fine tuning. Barr responds that, even if so, having such a rich multiplicity as to make life possible would itself be indicative of design. But that is questionable. If there exist, say, 700 trillion universes (or regions) and only one or a few of them are inhabited, should we assume the whole ensemble was set up to foster life? By Barr's standard, it seems that only if life were utterly impossible in all universes would there be a lack of evidence for design.

Barr rightly distinguishes between two types of design arguments: cosmic design arguments that focus on overall features of the universe; and biological design arguments that focus on characteristics of organisms. He propounds cosmic design, but also asserts that scientists have been too dogmatic in rejecting biological design. Yet what Barr, like many other design theorists, fails to recognize is that these two types of design are in tension with each other. If the laws of physics are fine tuned for life, then it is no surprise that life will evolve without further intervention. If intervention in biology is needed, that suggests the original fine tuning was inadequate in some way.

In the book's latter chapters, Barr focuses on questions of mind and free will. Following philosopher John Lucas and scientist Roger Penrose, he argues that the mathematical theorems of Kurt Gödel suggest that the human mind is not "just a computer." Barr argues that quantum mechanics provides an opening for free will by overthrowing determinism and predictability, and also suggests that the role of the observer in some interpretations of quantum mechanics suggests there is an immaterial aspect to the human mind. (Barr confuses matters by writing that an emphasis on consciousness is part of the "orthodox" interpretation of quantum mechanics. It would be more accurate to say it is an unorthodox interpretation that arose from ambiguities in the orthodox view.)

Barr presents an interesting discussion of these highly contentious matters. He is correct in noting that Heisenberg's uncertainty principle and Gödel's undecidability theorems were not reckoned with by materialists of a century ago. Still, even if Barr is right about mind and will (a big if), this would go only so far in bolstering his thesis about indications of God. One can believe, with existentialist philosophers such as Jean-Paul Sartre, that free will exists but God does not. One can also believe, as have Calvinists and others, that God exists but free will does not. The question of whether the human mind is replicable by a computer also does not strictly divide between theists and atheists.

But a larger problem for Barr is that even if one accepts his argument that the laws of physics suggest a designer, it is far from clear that this would be the God of the Judeo-Christian tradition. One could just as easily - indeed, more easily - argue that it is the God of deism, who created the world but takes no role or interest in it. The laws of physics, even if designed, seem thoroughly impersonal; they do not distinguish, as far as we can tell, between good people and bad, or adherents of different religions. Moreover, the miracles in the Bible are not readily explained by the laws of physics; on the contrary, they are regarded as miracles precisely because they contravene physical laws.