Science has flourished for three hundred years in the West, and has been in many ways a marvelous blessing to the world, but it may nevertheless soon find itself on life support. Ironically, the agent of its potential senescence is the rejection of a couple or three metaphysical assumptions that many credit with having given it its robust vigor and success in the first place.
The assumptions I refer to are these: 1. The conviction that science should limit itself to the study of natural, physical causes, and 2. that the theories it propounds should be based on physical, empirical evidence. Those theories, moreover, should 3. have the quality of being in principle falsifiable - that is, there should be a way to test the theory and a conceivable result of that test which, if it obtained, would show the theory to be false. Whatever hypotheses cannot meet these criteria - e.g. religious, ethical, epistemological, or aesthetic theories - belong to philosophical inquiry and reside outside the boundaries of science.
That's been the prevailing view ever since the Enlightenment, but there's sympathy in some scientific and philosophical precincts today for quietly doing away with both the need for empirical evidence as well as the falsifiability criterion, and the reasons for this, or at least a couple of them, are interesting.
Some scientists, for instance, think these criteria are too confining and, worse, they lead to unhappy metaphysical conclusions about the existence of God.
Specifically, some (many?) philosophers and scientists want desperately to legitimize multiverse hypotheses as legitimate science because if our universe is the only one that exists the conclusion that it is intentionally designed becomes virtually inescapable. As you might imagine, this ineluctability makes metaphysical naturalists (atheists) quite uncomfortable. As Bernard Carr, a cosmologist at Queen Mary University of London puts it, it's either the multiverse or God. Those are the only two live options.
The reason the multiverse seems necessary to save naturalism is that cosmic fine-tuning is so compelling (see video below), and the probability of a universe as incredibly fine-tuned as ours existing is so infinitesimally tiny, that if one wishes to avoid the conclusion that a supernatural Designer exists, or even the weaker but still important conclusion that the universe affords much evidence that such an intelligence exists, one has to hold that there's an infinite array of worlds in which every possible universe is actual. If so, then in an infinity of worlds every possible world has a probability of one, including our world. This would mean that the cosmic fine-tuning may be no big deal.
Thus, the multiverse is seen as the best way on offer to rescue naturalism from the theists. But the problem is there's no physical evidence that such a plethora of worlds really does exist, only that their existence is possible, nor is there any way to test or falsify the claim that this ensemble of worlds does exist. Thus, many philosophers and scientists argue, the multiverse theory is not a scientific hypothesis at all. It's metaphysics, just like religion, ethics, etc.
This "reduction" of the stature of the theory won't do, because if it's not a "scientific" theory it won't have any particular authority or claim on people's minds, so what's the solution? If the hypothesis doesn't meet the criteria of science then one solution is to drop the inconvenient criteria altogether so that science becomes simply whatever it is that scientists do. But this makes science something other than what it's been for three centuries. It robs it of its distinctive character and transforms it, as I said, into an exercise in metaphysics, just like religion.
There's another way science seems to be losing its distinctive character, and we'll look at that tomorrow.