There's scarcely any empirical evidence for the multiverse, however, and it's popularity among naturalists seems to stem largely from its utility as a response to the powerful argument for a cosmic Designer based on the incredible improbability that a universe like ours, with astonishingly precise values of the parameters that form the fabric of the universe and make life possible, would exist at all as a result of chance.
If, however, there's an infinite array of different universes with different laws and parameters, then even astronomically improbable universes are certain to be among that infinite manifold. Thus, as amazingly improbable as a life-sustaining world is, one pretty much had to exist, given the existence of the multiverse and we just happen to be in it, or at least that's the argument.
Nevertheless, as philosopher Vincent Torley points out in a lengthy treatment of the multiverse at Uncommon Descent there's a perplexing difficulty for the naturalist who clings to the multiverse in order to avoid falling into theism. If the multiverse exists then not only does the improbable become certain, but so, too, does anything that is possible to occur under some set of physical laws. This would, of course, include miracles.
Miracles are, after all, exceedingly improbable events given the laws which appear to govern our world, but they're not logically impossible. It's possible that the laws of some universe are structured in such a way that allows for miracles on very rare occasions. Such a world must exist somewhere in the multiverse and perhaps we just happen to be in it.
The irony is that the naturalist rejects the miraculous because he rejects belief in the existence of God, but in order to sustain his non-belief in God he relies on a hypothesis, the multiverse, that makes miracles virtually certain to occur somewhere in the vast ensemble of worlds that comprises the multiverse.
Naturalism sees our universe as invariant. That is, the laws of physics hold everywhere and always. They're inviolable. Thus, miracles, for the naturalist, are physically impossible, but as Torley points out, in a multiverse where all physical possibilities are instantiated there should be universes in which the laws of physics fluctuate episodically, thereby permitting anomalous events like miracles, and these universes should be far more common than uniformitarian worlds in which the laws are invariant.
Here's Torley:
[B]ecause multiverses allow laws to vary bizarrely on rare and singular occasions, and because not all such variations are fatal to life, we can conclude that a life-permitting universe is far more likely than not to experience anomalous events (which some might call miracles), and that a life-permitting universe in which Biblical miracles occur is still more likely than one in which the laws and physical parameters of Nature are always uniform.We'll have more to say about the difficulty that embracing the multiverse hypothesis poses for a naturalistic worldview tomorrow.
Thus [the] belief that we live in in a universe where Biblical miracles occurred will still be more rational than the modern scientific belief that we live in a universe whose laws are space and time-invariant, because [these] universes are more common in the multiverse than law-invariant universes.