My brother gave me Lee Smolin's polemic against string theory for Christmas. I now have to read in 2 minute bursts, but I finally finished it.
Smolin's basic point is that string theory has predicted no experimental result, and on its own account it is a highly incomplete precursor to a deeper "M theory" that no one has actually formulated. He makes a good case that its continued domination of theoretical physics is because of the political economy of the university, not its promise as a research program.
Obviously, I can say no more than that the man sounds plausible. If I can get more out of it than that, it is on points he raises in passing. For instance, à propos the Summers controversy, he testifies that in his experience, gender and racial biases are common in hiring decisions in physics.
He doesn't like the Copenhagen interpretation of quantum mechanics which so intimidated we philosophy students who couldn't understand it when I was a lad, and it is from him that I learned von Neumann's supposed proof that no hidden deterministic variables could explain quantum results was disproved by David Bohm.
Most interesting to me is his discussion of the "anthropic principle". As it has become clearer that string theory leads to a "landscape" of possible universes, the idea that the basic physical structure of the world can be explained on the basis that otherwise our existence would be impossible has become highly respectable.
The anthropic principle lends itself to at least two metaphysical interpretations. One is that God so ordered things because embodied intelligence was part of his plan. The other is that there is an infinitude of universes with other structures beyond the possibility of causal interaction with us, but we only observe one in which we could exist. These alternatives would have been familiar to the ancients. It seems clear that no experiment could decide between them - that the choice is one of preference and speculative argument - and therefore beyond science.
Smolin deplores the explanatory use of the anthropic principle, and I think he is right to do so. Whatever we use to explain is itself unexplained. If science gets to the point where it takes our existence as the explanans, rather than the explanandum, it is conceding a rather major defeat. Why should it do so unless it has absolutely no other choice? I agree with Smolin that positing an infinitude of causally-isolated worlds -- while perhaps true -- isn't science, because in principle no experiment could shed light on it one way or the other.
The best objection to Intelligent Design theory is similar to Smolin's objection to the anthropic principle. An intelligent (but inscrutable) designer explains everything and therefore nothing. No experiments are suggested: as John Derbyshire pointed out, it can't discover anything, Neither are science -- both are statements that science can't do something when we don't really know until it tries. Since science has discovered lots of stuff in the past, and shows no sign of slowing down, this seems like unwise defeatism. Smolin's plea to put resources behind other approaches that do not need the anthropic crutch therefore seems like a sensible one. (Perhaps a version of string theory can be developed that won't need it either.)
Of course, Smolin admits that his expectation that a theory in which our world comes out of the math, and not out of our (unexplained) presence will be developed is a matter of faith. It is perfectly possible that no such theory exists, or that it will never be discovered by human beings. But he'd say his faith is a healthy one for the scientific community, while a belief in string theory willing to sacrifice basic scientific method is an unhealthy faith.
Viewed as a philosophical proposition, rather than a rival scientific theory (as Daniel Larison wishes it would be), Intelligent Design does well especially if Smolin's faith is ultimately found to be justified. For if the world comes right out of the math, then we still have the mystery of how the physical can be so amazingly described by an intellectual construct like math. The unexplained fact is that facts can be explained, that they manifest an intelligible order. Here's a mystery that I doubt science could ever explain.