I recently got into a conversation with an apologist who used the "real infinities can't exist argument", and specifically was saying that it is impossible to have an infinite past. It essentially says that with an infinite past, you can't get to the present moment. I've explained before what the problem with this argument is, but that's not my focus today. For this article, I want to assume that the argument is valid and see what would follow.
The argument concludes that there must be a beginning. Granted, we all agree that this universe had a beginning at the big bang, the question is what came before that? What started that big bang? Many say that one possibility is a multiverse, or perhaps a contracting and expanding universe. This argument says that even given those possibilities, it is impossible for them to go backward in time forever. Whatever it is, it must start somewhere. Whether it is at the big bang, at an earlier iteration of our expanding and contracting universe, or at the beginning of the multiverse, there has to be an uncaused cause somewhere. They are, of course, happy to place God in this spot.
But I would argue that we have gained nothing here. By the exact same argument which says the multiverse can't go back infinitely into the past, God can't either. When I pointed this out, the apologist said that it doesn't apply to God because he's immaterial. The problem with this line of logic is the "no infinite past" argument never mentioned material. It either applies to matter and to God, or it fails for both. If God can be infinite, then their argument is invalid and it is possible that a multiverse could be infinite as well. If infinities are not possible then God has to have a beginning and he needs an explanation just as well as the first universe/multiverse.
"God is eternal, he's outside of time." This is the other response I hear a lot to this line of argumentation. I'll be honest, I'm not completely sure what that even means, but I don't think it matters if I do. If God can be outside of time, why can't other things be as well? Perhaps the multiverse is "outside of time". No matter what angle they take here, the apologist is basically trying to construct a problem for the multiverse but leaving a trap door for their God to solve that problem. As far as I can tell, this will inevitably lead to the multiverse itself fitting through that same trap door. Their only recourse seems to be to special pleading by simply insisting that only God can fill that role.