I wrote the post in order to get a hole in the logic of the Sequences fixed. And the argument I presented was chosen in order to be as simple and convincing as possible: the existence of a whole class of interpretations that are unaddressed in the Sequence, and which exist at approximately the same level of qualitative plausibility as many worlds, when judged by the pre-Copenhagen standards of mathematical physics.
You’re also wrong about my “real objections”, in two ways. The way you put it was that I want consciousness to be explained by something quantum, and MWI kills this hope. But in fact my proposition is that consciousness is based on entanglement—on a large tensor factor of the quantum state of the brain. MWI has no bearing on that! MWI is entanglement-friendly. If some other version of quantum theory says there’s entanglement in the brain, that entanglement will still be present in many-worlds. (Retrocausal theory is actually much less entanglement-friendly, because it generally doesn’t believe in wavefunctions as physical objects.) My philosophy-of-mind objections to MWI-based theories of personhood have to do with MWI tolerance of vagueness regarding when one person becomes two, and skepticism that a branching stream of consciousness is even logically possible.
But more importantly, the other criticisms of MWI that I make are just as “real”. I really do consider a large fraction of what is written in support of MWI, to be badly thought out, describing ideas which aren’t a physical theory in any rigorous sense. I really do think that the only reasonable way to explain the Born probabilities is to exhibit a multiverse in which those are the actual frequencies of events, and that this is not the case for 99% of what is written about MWI. I really do think that the problem posed for MWI by relativity is not properly appreciated.
Despite all this, I’m willing to engage with MWI a little because it still has some microscopic chance of being true, and also because it does have roots in the formalism. I believe the way to the answer does not just involve pluralism of research, but active hybridization of interpretations, especially at their points of contact with the mathematical theory.
I wrote the post in order to get a hole in the logic of the Sequences fixed. And the argument I presented was chosen in order to be as simple and convincing as possible: the existence of a whole class of interpretations that are unaddressed in the Sequence, and which exist at approximately the same level of qualitative plausibility as many worlds, when judged by the pre-Copenhagen standards of mathematical physics.
You’re also wrong about my “real objections”, in two ways. The way you put it was that I want consciousness to be explained by something quantum, and MWI kills this hope. But in fact my proposition is that consciousness is based on entanglement—on a large tensor factor of the quantum state of the brain. MWI has no bearing on that! MWI is entanglement-friendly. If some other version of quantum theory says there’s entanglement in the brain, that entanglement will still be present in many-worlds. (Retrocausal theory is actually much less entanglement-friendly, because it generally doesn’t believe in wavefunctions as physical objects.) My philosophy-of-mind objections to MWI-based theories of personhood have to do with MWI tolerance of vagueness regarding when one person becomes two, and skepticism that a branching stream of consciousness is even logically possible.
But more importantly, the other criticisms of MWI that I make are just as “real”. I really do consider a large fraction of what is written in support of MWI, to be badly thought out, describing ideas which aren’t a physical theory in any rigorous sense. I really do think that the only reasonable way to explain the Born probabilities is to exhibit a multiverse in which those are the actual frequencies of events, and that this is not the case for 99% of what is written about MWI. I really do think that the problem posed for MWI by relativity is not properly appreciated.
Despite all this, I’m willing to engage with MWI a little because it still has some microscopic chance of being true, and also because it does have roots in the formalism. I believe the way to the answer does not just involve pluralism of research, but active hybridization of interpretations, especially at their points of contact with the mathematical theory.