I see two issues in formulating a response to this question. First, does the multiverse conflict with Christianity? Second, how does the multiverse impact apologetics? I have addressed the former question in a previous TNRTB so I will focus on the latter question here.
In order for a strictly naturalistic multiverse model to provide an adequate explanation for this universe and our existence, it must meet a number of requirements.
First, the multiverse model must be self-contained. Christianity argues that the universe has a beginning (and thus a cause, or Beginner) and that the universe exhibits design such that human life has a suitable habitat. A naturalistic model cannot exhibit a beginning or true design because that requires an external agent—a Beginner or a Designer. Thus, any multiverse model must explain the apparent design acknowledged by the scientific community without having any aspect of the model reflect fine-tuning.
Second, any successful multiverse model must account for all observations and data. In other words, any proposed multiverse model must naturally produce a region that looks like this observable universe. Additionally, any multiverse model must also make predictions about what scientists will detect in our observable universe. Otherwise, no scientific tests can verify or falsify the model because, by definition, the proposed multiverse forever lies beyond the reach of observations.
Third, the models must provide a mechanism that produces a sufficient variety of universes. A popular argument says that a monkey typing away for an enormously long time will eventually reproduce the complete works of Shakespeare. However, the argument is only true if the keyboard contains all the letters of the alphabet as well as any necessary punctuation. With a keyboard of vowels only, the monkey will never produce any readable work regardless of how long it types. Similarly, unless a multiverse model produces a sufficient variety of universes, it cannot explain the fine-tuning observed in the laws of physics, the fundamental constants, and the characteristics of Earth, Sun, Moon, planets, and galaxy.
Fourth, our universe must be one possible outcome in the multiverse model. Otherwise the model is like a keyboard with no “e.”
Fifth, and most importantly, life must be completely physical. Although this requirement flows from the first, it bears separate mention to highlight its importance. All multiverse models I have encountered so far implicitly make the assumption that life is completely physical. However, if human life has a nonphysical component, such as the image of God, then no amount of twiddling the laws of physics and rearranging the stuff of the universe will produce a human being without divine intervention.
In evaluating multiverse models, one must keep these requirements in mind. I think it reasonable for the naturalist to assume that inflationary cosmology could produce a large number of universes that operate under different laws of physics and that this universe is one of those universes. Although both of these assumptions need further verification, multiverse advocates have put forth models currently consistent with requirements three and four.
In contrast, I have shown how robust arguments demonstrate that the multiverse must still have a beginning. Thus a strictly naturalistic multiverse fails the first requirement.
Similarly, the idea of Boltzmann brains means that our universe appears odd in the multiverse. Remember, sentient life abounds in a naturalistic multiverse model. Either the existence of Boltzmann brains means that we are atypical observers or the multiverse-generating mechanism must be fine-tuned in order to not produce Boltzmann brains. Either way, our existence appears fine-tuned. Once again, the naturalistic multiverse fails the first requirement.
In the next two “Multiverse Musings” I want to address the second and fifth requirements. An important piece of evidence for the observable universe’s geometry as well as last month’s musings indicate that multiverse models may not pass requirement two.
I am almost 100% confident that a Level I multiverse exists. However, I would argue that the term “multiverse” in this context is somewhat of a misnomer. After all, the essential point of a Level I multiverse is simply that space does not end at the farthest reaches astronomers can observe. From a scientific perspective, a Level I multiverse fails requirement three. I am more ambivalent about the existence of a Level II multiverse. Mainstream scientific views on inflation provide some evidence for a Level II multiverse, although much more speculatively than Level I.
In the end, I don’t personally see any significant biblical problems with God creating a multiverse that accounts for some of the design aspects of our universe. On the other hand, even if the multiverse exists, it still poses significant problems for a strictly naturalistic view.
If you would like to see a question about the multiverse addressed in this forum, send it to firstname.lastname@example.org.