Recall that Edward Witten, another Fields medal winner and the guru of the string theorists, has deduced from the mathematical structure of string theory that the 21st century mathematics will be dominated by string theory, raising the eyebrows of his less predictive colleagues. Only people without any intuition and without any knowledge of contemporary theoretical and mathematical physics can suggest that string theory can't make predictions.I commented that this is a feeble example of a prediction, and Motl responded:
Dear Roger, it is by no means the only example.
String theory predicts supersymmetry below the Planck scale, 6 or 7 extra dimensions below the Planck scale, the detailed properties of all particles and interactions as a function of a finite set of discrete input parameters, black hole thermodynamics in agreement with Hawking calculations including infinitely many corrections to these black holes, possible properties of axions, candidates for dark matter, and so forth, and so forth.
String theory is the dominant idea underlying theoretical physics and much of mathematics, and it will be increasingly so as this century and millenium continues. It is the only framework different from ad hoc effective field theories that can be used to organize new insights that will be seen in the future and the only framework that can be used to make predictions beyond effective field theory.
I think that string theory will continue to be an influential branch of Mathematics, but it has not made any predictions about the physical world. Nothing below the Planck scale is observable. Supersymmetry makes some predictions, but the reasons for and against believing in supersymmetry have little to do with string theory.
String theory certainly does not predict "the detailed properties of all particles and interactions" as it doesn't even predict any properties of any particles. The axion is a speculative candidate for dark matter, but it didn't come from string theory and string theory has little to say about it. If it turns out that axions do not exist, then the string theorists will be unfazed.
If Motl really had some observable predictions, he'd be posting them, and not just abusing those who disagree with him.
Update: Motl's response is to say, "whole classes of string theory do predict axions" and to call me a creationist. No, I am not a creationist. The article tries to give properties of axions in order to solve the cosmological dark matter problem, but those properties contradict what the cosmologists say is necessary.
It is amazing how sensitive string theorists are about whether their work is scientific. I think that Motl brings up creationism so that he can say that they are more scientific than the creationists. That is not saying much. If he were really doing scientific work, then he would just point to it, and drop the silly name-calling.