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vanesch said:This is always the same misunderstanding. There is ONE Bob's body, but there are, if you want, TWO Bob-experiences, one of which is the continuation of the original (and whether, or not, the other is "mindless" or "came into existence as a copy" doesn't really matter - but if you don't like the mindlessness, just consider it to be a "copy that came into existence"). It is the one that is the continuation of the original that follows the Born rule. Now, if you prefer that the other copies also are conscious (it that eases your mind), you can postulate for them what you want ; for instance that they will ALSO follow subsequently the Born rule. But all those considerations have no implications what so ever on any observable thing - so it is completely open to your personal preferences.
Apparently I didn't make clear what bothers me. I'm happy to set aside the silliness of there being two Bobs, one in each branch that occurs after Bob makes a measurement. And I concede that your idea of choosing, at random, by the Born rule, one of those branches for Bob's consciousness-token to follow, allows for a consistent picture from Bob's POV.
You suggest that if I'm unhappy with the mindless hulks, I should just add additional consciousness tokens during each branching. That's also not really what I was getting at, but wouldn't this become a serious flaw for this model then? Suppose Bob makes a measurement on some state such that there is 90% probability for outcome A and 10% for outcome B. Well, if I add the extra consciousness token, now both branches will with certainty contain such a token. In other words, it is now 100% certain that both outcomes are equally real, equally experienced by Bob. How are you going to then explain the meaning of those original 90/10% probabilities? Your way of giving such probabilities meaning in the original theory (there is a 90% chance that Bob's consciousness moves from an "i'm about to perform this experiment" state to a "i just performed it and got outcome A" state) is ruined by making all the subsequent branchings equally blessed by a token. Or do I misunderstand something?
Anyway, what was really bothering me about this was how fast and loose it plays with the idea of what "really happens". Basically, this notion is cashed out in this theory in terms of the consciousness tokens following one or the other of the branches. So, going back to the original one-token model, what "really happens for Bob" (i.e., what Bob actually experiences to be real) is (say) outcome A. And one can make a similar comment about what "really happened" for Alice. And then you want to tell this story about Alice and Bob getting together later to compare notes, and you want to claim that they agree just the right fraction of the time, so voila, we have a local explanation of the correlations. My point was just to flesh out with more clarity what exactly this involves. Usually MWI people talk as if it "merely" involves rejection of the idea that the outcomes on each side are definite. But look at the consequences of that: at the coffee shop, the "real outcomes" of Alice and Bob are *never compared*. And you can't get around having some notion of "real outcomes" becuase it's just an empirical fact that if a person makes one of these measurements, he finds himself afterwards believing that it had a definite outcome (a belief which is false according to MWI, but so what -- we can just use that belief to redefine "real"). So that's my point. It's not just that Alice is in the uncomfortable situation of being still in a superposition until she gets to the coffee shop, at which time all the superpositions are resolved and everything is OK. No. Rather, the "real" Alice goes to the coffee shop, but she never ends up having the intended conversation with the "real" Bob. They never meet (because, at least sometimes, their cs-tokens are in different branches). So the intended comparison of outcomes from the two sides never in fact happens.
I don't think this is a new point to you, and I certainly don't expect you to change your mind about MWI because of it. I just wanted to clarify for others how extreme a price you pay for going down this route.
As I said, if this disturbes you, then "create" new sentient minds during the split, it doesn't matter, as long as the *original* mind follows the Born rule - in fact, as long as YOUR mind follows the Born rule.
Yes, it does tend to come back to that solipsistic attitude, doesn't it? As long as all we're ever *really* talking about is my beliefs (how things "appear" to me, etc.) then the theory "works". But then unfortunately it no longer makes any sense to describe the theory as local. If everything I take to be an external world is really a (deluded) belief in my head, then it makes no sense to claim that causal interactions in the external world are always sub-luminal.
What counts is how the world APPEARS wrt a particular observer, and that's good enough, no ?
Not for me. But that's subjective. But the point we should in principle be able to agree about is this: claims about "locality" are literally meaningless if what the theory turns out to be fundamentally *about* is mere appearances/beliefs.
But you can have a perfectly normal conversation with a mindless hulk, or with a COPY of a sentient being, no ? BY DEFINITION, there is no difference in their behaviour. They will answer in the same way. How do you KNOW that your wife is not "a perfect copy of your wife" ?
With or without consciousness ?
Trust me, I know! :tongue2: