I think I agree it makes verificationism a bit more plausible if you already find Tegmark IV plausible.
Regarding the quantum multiverse—yes, I agree, that is the usual way of thinking about things, moreover the usual thinking is that most ordinary statements about the future are similarly indeterminate. On the other hand, this isn’t the usual thinking about the cosmological multiverse. In a quantum multiverse, universes literally branch, in a cosmological multiverse, universes merely diverge. So, assuming the usual views about these multiverses are correct, would Level IV be like the quantum multiverse or would it be like the cosmological multiverse?
I can see both ways, but on reflection, it seems more natural to say it’s like the quantum multiverse. On the cosmological picture, for every consistent mathematical structure, you’ve got a separate self contained world, and there can be a lot of duplicate structure across worlds, but there can’t be duplicate worlds. It seems to make a weird distinction between worlds and the substructures in worlds. On the quantum picture, you can think of the observer as a mathematical structure in its own right, that is instantiated in many different larger structures, and there’s no fundamental notion of “world”.
So fine, this gives you something like verificationism.
I’m not sure what you mean by cosmological multiverse.
Re distinction between branching and diverging—I think even without adopting verificationism, one can plausibly argue that that distinction is meaningless.
By cosmological multiverse, I mean Level I or II.
It is arguable that the distinction between branching and diverging is meaningless, or that Level I and II should be viewed as branching, but that is not the usual view.
I think it’s clear it’s not meaningless, and that those who think it’s meaningless just favor viewing every kind of splitting as branching. Let me explain:
To say the future branches, what I mean is that there is no fact of the matter what exactly will happen in the future.
To say the future diverges, what I mean, is that there is a fact of the matter about what will happen in the future, but that there are observers just like me who will observe a different future.
Either there is a fact of the matter what will happen in the future, or there isn’t (?!). It may indeed be the case that the concept of diverging is incoherent, in which case the only kind of splitting is branching. This is a heterodox view, however.
I think I agree it makes verificationism a bit more plausible if you already find Tegmark IV plausible.
Regarding the quantum multiverse—yes, I agree, that is the usual way of thinking about things, moreover the usual thinking is that most ordinary statements about the future are similarly indeterminate. On the other hand, this isn’t the usual thinking about the cosmological multiverse. In a quantum multiverse, universes literally branch, in a cosmological multiverse, universes merely diverge. So, assuming the usual views about these multiverses are correct, would Level IV be like the quantum multiverse or would it be like the cosmological multiverse?
I can see both ways, but on reflection, it seems more natural to say it’s like the quantum multiverse. On the cosmological picture, for every consistent mathematical structure, you’ve got a separate self contained world, and there can be a lot of duplicate structure across worlds, but there can’t be duplicate worlds. It seems to make a weird distinction between worlds and the substructures in worlds. On the quantum picture, you can think of the observer as a mathematical structure in its own right, that is instantiated in many different larger structures, and there’s no fundamental notion of “world”.
So fine, this gives you something like verificationism.
I’m not sure what you mean by cosmological multiverse.
Re distinction between branching and diverging—I think even without adopting verificationism, one can plausibly argue that that distinction is meaningless.
By cosmological multiverse, I mean Level I or II. It is arguable that the distinction between branching and diverging is meaningless, or that Level I and II should be viewed as branching, but that is not the usual view.
I think it’s clear it’s not meaningless, and that those who think it’s meaningless just favor viewing every kind of splitting as branching. Let me explain: To say the future branches, what I mean is that there is no fact of the matter what exactly will happen in the future. To say the future diverges, what I mean, is that there is a fact of the matter about what will happen in the future, but that there are observers just like me who will observe a different future.
Either there is a fact of the matter what will happen in the future, or there isn’t (?!). It may indeed be the case that the concept of diverging is incoherent, in which case the only kind of splitting is branching. This is a heterodox view, however.
So your claim that it’s not meaningless is basically just the negation of my third premise.