I confess I don’t really understand what problem this is attempting to show us, that explains why we shouldn’t think of duplication and probability as alike and why Stuart has become less keen on “many worlds” approaches to QM. I mean, it describes some questions one can ask, and (so far as I can see) then just gestures towards them and invites us to feel bad about those questions. It seems like I’m missing a step in the argument.
Certain duplication is not the exact same thing as probability. But who ever said it was?
It is, however, somewhat like probability, and I don’t see anything in this post that should change anyone’s opinion about that.
It seems as if what Stuart says about “the thread of conscious experience” is intended to be an argument against the Everett interpretation, but I don’t understand why. There’s nothing consciousness-specific about quantum measure (or about probability); there is some sense in which, if mutually exclusive and exhaustive events A and B happen with measures 0.1 and 0.9 respectively, “9x as much of you” ends up in the B-worlds as in the A-worlds, but what does this mystical thread-of-experience language gain for us? It seems to me that these differences in measure are relevant precisely because they correspond to differences in probability, and e.g. I care 10x more about what happens to me in futures that are 10x as likely. Is there supposed to be something illegitimate about that?
It is, however, somewhat like probability, and I don’t see anything in this post that should change anyone’s opinion about that.
How “somewhat”? The kind of behaviour I’m talking about—flipping the lever and letting your copy deliver the message—violates the independence axiom of expected utility, were duplication a probability.
As for why I’m less keen on MWI, it’s simply that I see a) duplication is not a probability b) duplication with a measure doesn’t seem any different to standard duplication, and c) my past experience causes me to see measure as (approximately) a probability.
Hence, MWI seems wrong. You probably disagree with a) or b), but do you see the deduction?
Again, I’m not saying that (“in-universe”) duplication is exactly the same as probability, and neither is everyone else. Duplication is like probability in, e.g., the following sense: Suppose you do a bunch of experiments involving randomization, and suppose that every time you perform the basic operation “pick one of N things, all equally likely, independently of other choices” what actually happens is that you (along with the rest of the universe) are duplicated N times, and each duplicate sees one of those N choices, and then all the duplicates continue with their lives. And suppose we do this many times, duplicating each time. Then in the long run almost all your duplicates see results that look like those of random choices.
I can, of course, see the inference from “in-universe duplication is not essentially the same as probability” + “in-universe duplication is essentially the same as cross-universe duplication” + “MWI says cross-universe duplication is essentially the same as probability” to “MWI is wrong”, at least if the essentially-the-same relation is transitive. But I disagree with at least one of those first two propositions; exactly which might depend on how we cash out “essentially the same as”.
(I’m not sure whether the paragraph above is exactly responsive to what you said, because you didn’t say anything about the distinction between in-universe and cross-universe duplication, which to me seems highly relevant, and because I’m not sure exactly what you mean by “duplication with a measure”. Feel free to clarify and/or prod further, if I have missed the point somehow.)
I confess I don’t really understand what problem this is attempting to show us, that explains why we shouldn’t think of duplication and probability as alike and why Stuart has become less keen on “many worlds” approaches to QM. I mean, it describes some questions one can ask, and (so far as I can see) then just gestures towards them and invites us to feel bad about those questions. It seems like I’m missing a step in the argument.
Certain duplication is not the exact same thing as probability. But who ever said it was?
It is, however, somewhat like probability, and I don’t see anything in this post that should change anyone’s opinion about that.
It seems as if what Stuart says about “the thread of conscious experience” is intended to be an argument against the Everett interpretation, but I don’t understand why. There’s nothing consciousness-specific about quantum measure (or about probability); there is some sense in which, if mutually exclusive and exhaustive events A and B happen with measures 0.1 and 0.9 respectively, “9x as much of you” ends up in the B-worlds as in the A-worlds, but what does this mystical thread-of-experience language gain for us? It seems to me that these differences in measure are relevant precisely because they correspond to differences in probability, and e.g. I care 10x more about what happens to me in futures that are 10x as likely. Is there supposed to be something illegitimate about that?
How “somewhat”? The kind of behaviour I’m talking about—flipping the lever and letting your copy deliver the message—violates the independence axiom of expected utility, were duplication a probability.
As for why I’m less keen on MWI, it’s simply that I see a) duplication is not a probability b) duplication with a measure doesn’t seem any different to standard duplication, and c) my past experience causes me to see measure as (approximately) a probability.
Hence, MWI seems wrong. You probably disagree with a) or b), but do you see the deduction?
Again, I’m not saying that (“in-universe”) duplication is exactly the same as probability, and neither is everyone else. Duplication is like probability in, e.g., the following sense: Suppose you do a bunch of experiments involving randomization, and suppose that every time you perform the basic operation “pick one of N things, all equally likely, independently of other choices” what actually happens is that you (along with the rest of the universe) are duplicated N times, and each duplicate sees one of those N choices, and then all the duplicates continue with their lives. And suppose we do this many times, duplicating each time. Then in the long run almost all your duplicates see results that look like those of random choices.
I can, of course, see the inference from “in-universe duplication is not essentially the same as probability” + “in-universe duplication is essentially the same as cross-universe duplication” + “MWI says cross-universe duplication is essentially the same as probability” to “MWI is wrong”, at least if the essentially-the-same relation is transitive. But I disagree with at least one of those first two propositions; exactly which might depend on how we cash out “essentially the same as”.
(I’m not sure whether the paragraph above is exactly responsive to what you said, because you didn’t say anything about the distinction between in-universe and cross-universe duplication, which to me seems highly relevant, and because I’m not sure exactly what you mean by “duplication with a measure”. Feel free to clarify and/or prod further, if I have missed the point somehow.)