John Byl has posted a critique of Don Page’s theistic multiverse:
Since Prof. Byl has a doctorate in astrophysics, he’s better qualified than most to evaluate the scientific merits of the theory.
i) Because a theistic multiverse is speculative, I don’t think Christians who are sympathetic to that position should erect a theological edifice over that conjectural foundation. At the same time, the denial of a theistic multiverse is equally speculative.
ii) Dr. Byl targets a scientific version of the multiverse, based on Everett’s interpretation of quantum mechanics. Since Page is propounding a scientific version of the multiverse, his model can be evaluated on scientific grounds.
iii) However, we need to distinguish between physical models of the multiverse, like Everett’s many-worlds version–and metaphysical models, like David Lewis’s concrete modal realism. Scientific criticisms of the former bounce off the latter. Byl’s post leaves the impression that by disposing of Page’s model, he has thereby done away with the multiverse tout court. But that’s clearly overstated.
iv) One conventional objection to the multiverse, which Byl lodges, is the unverifiable or unfalsifiable nature of the hypothesis. That raises a number of issues:
a) Proponents would say there’s indirect evidence for the multiverse. They’d say there’s evidence for quantum mechanics, and they’d say Everett’s interpretation is the best interpretation of quantum mechanics. Of course, that’s disputed, but that’s the argument.
b) On the face of it, postulating a multiverse is no more unscientific than postulating other theoretical entities, like quarks. The justification for postulating theoretical entities is their explanatory value. We shouldn’t stop at the level of observables. For one thing, what’s observable or unobservables varies depending on the state of our technology. What was unobservable in the 15C is observable in the 21C based on technological advances.
Likewise, take a diagnostician who’s trying to find out what’s wrong with a patient. Based on a battery of tests, something is objectively abnormal about the patient’s health. Suppose the diagnostician fails to detect the source. Still, it’s reasonable for the diagnostician to think something must be causing the patient’s medical problem, even if he can’t discover the source of the problem.
Similarly, when we reconstruct the past, we postulate things to fill in the gaps. If we unearth a partial skeleton, we interpolate the missing parts. We don’t assume the organism, when it was alive, had a partial skeleton.
c) Having said that, a problem with theoretical entities is that more than one kind of entity or combination of entities might be responsible for the effect. So the postulate will be underdetermined by the evidence.
v) Byl also objects to the way Page treats natural or physical laws. In fairness to Page, appeal to a natural law theodicy or stable environment is nothing new. And it has a grain of truth. For instance, mountain-climbers can’t expect God to suspend the “law” of gravity when they slip and fall.
That said, I agree with Byl that it’s easy to take this principle too far, as if God’s hands are tied once he initiates a system of second causes. But God doesn’t stand in awe of natural laws. They don’t inhibit divine action.
vi) It’s not entirely clear why Byl rules out a multiverse. Is he saying God is able, but unwilling to create a multiverse–or is he saying there is no multiverse because God is unable to create a multiverse? It seems to me that the latter represents an arbitrary restriction on divine freedom and omnipotence.
vii) Byl claims that, according to Scripture, God only created one world. However, there’s a danger of anachronism in that claim. Isn’t the universe to an ancient man what the multiverse is to a modern man? What did the “cosmic” references in Scripture mean to the original audience? Wasn’t their concept of the cosmos basically limited to the visible solar system? Naked-eye astronomy? No telescopes, spectroscopy, or radio astronomy. If you told them God created billions of other solar systems in billions of unobservable galaxies, would that count as one world or many worlds from an ancient perspective?
viii) Byl raises some theological issues that aren’t unique to a multiverse. One can raise similar issues if there’s intelligent life elsewhere in the universe. Aliens with a religious history particular to their own planet. Indeed, Byl has discussed that issue in the past.
ix) On a model of the multiverse like Everett’s, all physically possible outcomes are automatically realized. But on a metaphysical model, God can exercise discretion as to what possibilities will be exemplified.