I think the argument of Part 1 is a good one, but it does not quite establish its conclusion: While it is highly likely, given IBE, that chance is not the true account of the regularity of the universe, metaphysically necessary causal connections are not the only alternative. Indeed, in some cases they are seemingly not even a possible alternative. For quantum mechanics tells us, on most of its interpretations, that many of the most basic regularities in nature are probabilistic. Unless we’re prepared to posit “probabilistic necessities”—i.e., that it could be necessary that something happens only in a certain percentage of cases—many of the regularities described by quantum mechanics cannot be necessary. So how could we explain them?
If we accept theism, there is a way. God, being all powerful, could surely act in such a manner that certain things happen only with a certain frequency, not all the time. But God, according to theists, is not merely some convenient metaphysical explanatory posit. He is a personal being. While perhaps not having a psychology like ours—God probably doesn’t think discursively, with one thought following after another—He is nevertheless an agent who acts for the sake of ends. Provided that those ends include creating a word that is regular—perhaps because only such worlds are hospitable to life or sentience—it would be extremely probable, or even certain, that such a world would be actual.
Now, if we consider the matter in terms of “epistemic possibility”, there are many “possible Gods”, or “ways God could be”. A great deal of them would have no desire to create worlds that are regular. I don’t know of any good arguments to the effect that such “Gods” couldn’t have existed, so we can’t rule them out a priori. Instead, I think a theist should insist that given our actual evidence we aren’t justified in believing in them, because it is only if we posit a God who desires to create a world that exhibits regularities, albeit probabilistic ones, that we have reason to suspect such a world to be actual. If there is such a God we certainly have a better account than we would have if we thought such regularities were merely “an outrageous run of luck”. So the observed regularities in nature do cry out for explanation, but on this view their probabilistic nature favors a theistic account. Given the constancy of God’s nature and purposes, we are can confidently expect them to persist in the future. The above account, if true, would not constitute an airtight proof that the inductive schema of Part 1 is reliable, but I think it would give us a good (though defeasible) reason to accept it.
But all is not well. In Part 3 I’ll examine a couple objections to this account.