there’s no coherent concept of ‘world’ left to debate.
Good! Maybe we’re on the same page there. “World” is not part of the theory and is not a well-defined concept, in my opinion.
now you need to make ‘mind’ a rigorous concept
Hmm, I guess I would propose something like “the complete history of exactly which neurons in a brain fire at which times, to 1μs accuracy, is a mind, for present purposes”. Then I would argue that different “minds” don’t exhibit measurable quantum interference with each other, or we can say “different minds are in different worlds / branches” as a casual shorthand for that, if we want. And there is a well-defined (albeit complicated) way to project the universal wavefunction into the subspace of one “mind”, in order to calculate its quantum amplitude, and then you can apply the Born rule for the indexical calculation of how likely you are to find yourself in that mind. Something like that, I guess. I haven’t thought it through very carefully, I just think something vaguely like that could work, with a bit more effort to iron out the details. I’m not sure what’s in the literature, maybe there’s a better approach...
Good! Maybe we’re on the same page there. “World” is not part of the theory and is not a well-defined concept, in my opinion.
Hmm, I guess I would propose something like “the complete history of exactly which neurons in a brain fire at which times, to 1μs accuracy, is a mind, for present purposes”. Then I would argue that different “minds” don’t exhibit measurable quantum interference with each other, or we can say “different minds are in different worlds / branches” as a casual shorthand for that, if we want. And there is a well-defined (albeit complicated) way to project the universal wavefunction into the subspace of one “mind”, in order to calculate its quantum amplitude, and then you can apply the Born rule for the indexical calculation of how likely you are to find yourself in that mind. Something like that, I guess. I haven’t thought it through very carefully, I just think something vaguely like that could work, with a bit more effort to iron out the details. I’m not sure what’s in the literature, maybe there’s a better approach...