Well, personally I’d say not much. But I’m pretty Bayesian—or more accurately, I believe that much of the meaning of probability statements as used in scientific theories is a committment to, or recommendation of, certain decisionmaking (”betting”) behavior.

In this situation, though, it’s important to note that I’m paraphrasing my recollection of what Alan said, and he may not have used the word “predicting”. Maybe understanding, explaining, or maybe just something like “I’m interested in the frequencies with which things occur, not in betting”. I think this is the tip of an iceberg of philosophical difference about the role of probability in scientific theories, between me and those physicists attracted to the idea that quantum probability is about frequencies. There do seem to be a lot of people who think, to put it in a relatively plausible-sounding way, that probability in science is about an attempt to describe, in a compact way, the frequencies with which various properties are associated with each other, given that we can’t do so with deterministic laws of invariable association. They just want to describe, at a somewhat coarse-grained level, features of the block universe such as what fraction of portions of the universe with property A also have property B.

What’s the difference?