I think there’s a difference between A) making an argument for something that relies on untestables, and B) assuming some untestables and seeing what they would imply if true. I read this post more as the latter, though you could read it as the former as well.
Also, while MWI and the mathematical multiverse hypothesis seem untestable, I thought the lower levels of Tegmark’s hierarchy were testable? I remember Tegmark citing various kinds of empirical evidence in favor of his levels I and II, and also seem to recall hearing of later experiments that would have been evidence against level II (but I know very little physics, so I might have misunderstood those experiments).
The OP does not say “let’s assume that...”, but rather references the multiverse offhandedly, like it’s a fact, without even specifying which of the many multiverse models it uses.
As for Tegmark I and II, it is not clear whether the chaotic inflation model will be testable some day. Certainly our current understanding of quantum gravity is woefully insufficient to even make an educated guess as to whether and when and how it can happen. By then I expect that even the multi-level picture itself will be considered naive and outdated.
I think there’s a difference between A) making an argument for something that relies on untestables, and B) assuming some untestables and seeing what they would imply if true. I read this post more as the latter, though you could read it as the former as well.
Also, while MWI and the mathematical multiverse hypothesis seem untestable, I thought the lower levels of Tegmark’s hierarchy were testable? I remember Tegmark citing various kinds of empirical evidence in favor of his levels I and II, and also seem to recall hearing of later experiments that would have been evidence against level II (but I know very little physics, so I might have misunderstood those experiments).
The OP does not say “let’s assume that...”, but rather references the multiverse offhandedly, like it’s a fact, without even specifying which of the many multiverse models it uses.
As for Tegmark I and II, it is not clear whether the chaotic inflation model will be testable some day. Certainly our current understanding of quantum gravity is woefully insufficient to even make an educated guess as to whether and when and how it can happen. By then I expect that even the multi-level picture itself will be considered naive and outdated.