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Wei_Dai comments on MWI, copies and probability - Less Wrong
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Comments (127)
Another way to think about this is that many of us seem to share the follow three intuitions about non-interacting extra copies, out of which we have to give up at least one to retain logical consistency:
_
Another possibility is to hold a probabilistic superposition of these three positions, depending on the relative strengths of the relevant intuitions in your mind.
Very nice! In this setting, my position is to give up both 2 (because I don't believe moral intuition works adequately to evaluate this situation) and 3 ("complexity of value" argument: even if we do value spatially separated copies, it's not at all in the same way as we value MWI copies), while accepting 1 (for moral intuition, quantum branches are analogous to probability, where normal/classical situations are concerned).
Is there any evidence for 1: "We value extra copies in other quantum branches"...?
Who does that? It seems like a crazy position to take - since those are in other worlds!
Rejecting a p(0.5) grenade is not "valuing copies in other quantum branches." It is simply not wanting to die. Making such a decision while not knowing how the probabilty will turn out works just the same classically, with no multiple copies involved. Evidently the decision has nothing to do with "valuing multiple copies" - and is simply the result of the observer's uncertainty.
Me. Valuing existence in as much Everett branch as possible sounds like one of the least arbitrary preferences one could possibly have.
How does it compare to wanting to make a large positive difference in as many Everett branches as possible?
Roughly equal up until the point where you are choosing what 'positive difference' means. While that is inevitably arbitrary it is arbitrary in a, well, positive way. While it does seem to me that basic self perpetuation is in some sense more fundamental or basic than any sophisticated value system I don't endorse it any more than I endorse gravity.
We can construct less intuitive setup. You have created 99 copies of self.
Then every copy gets fake grenade (which always gives $100). Original you get real grenade. After explosion/nonexplosion remaining "you"s are merged. Will you accept next grenade in that setup?
I would be fine with that - assuming that the copies came out with the extra money; that the copying setup was reliable, etc.
This apparently has little to do with valuing "extra copies in other quantum branches" though - there is no "Everett merge" procedure.
Can I sum it as: if you know that "backup copies" exist then it's OK to risk being exploded? Do you care for being backed up in all Everett branches then? Or is it enough to backup in branch where grenade explodes?
The usual idea of a "backup" is that it can be used to restore from if the "original" is lost or damaged. Everett worlds are not "backups" in that sense of the word. If a quantum grenade kills someone, their grieving wife and daughters are not consoled much by the fact that - in other Everett worlds - the bomb did not go off. The supposed "backups" are inaccessible to them.
Kirk and Scotty would say yes.
While for the purposes of this discussion it makes no difference, my understanding is that the "Everett branches" form more of a mesh if you look at them closely. That is, each possible state for a world can be arrived at from many different past states, with some of those states themselves sharing common ancestors.
Maybe - but that is certainly not the conventional MWI - see:
"Why don't worlds fuse, as well as split?"
Yes, entropy considerations make recombining comparatively rare. Much like it's more likely for an egg to break than to recombine perfectly. Physical interactions being reversible in principle doesn't mean we should expect to see things reverse themselves all that often. I doubt that we have a substantial disagreement (at least, we don't if I take your reference to be representative of your position.)
You don't seem to realise that under the many worlds interpretation, the probabilities of the different outcomes of quantum events correspond (roughly speaking) to the amplitudes assigned to different universes, each of which contains instances (i.e. 'copies') of you and everything else. In other words, under MWI there is no difference between 'wanting to maximize your quantum probability of survival' and 'valuing copies of yourself in future quantum branches'.
[Note that I've substituted the word future for other. Whether A = "you at time t0" cares about B and C = "two different copies of you at time t1", both of which are 'descendants' of A, is a somewhat different question from whether B cares about C. But this difference is orthogonal to the present debate.]
If you want to simply deny the MWI then fine but you should acknowledge that that's ultimately what you're disagreeing with. (Also, personally I would argue that the only alternatives to the MWI are either (a) incoherent like Copenhagen (b) unparsimonious like Bohm's interpretation or (c) contain unmotivated deviations from the predictions of orthodox quantum mechanics (like the GRW theory).)
The phenomenon has nothing to do with quantum theory. You get the same result if the grenade depends on a coin toss - and the grenade recipient is ignorant of the result. That is the point I just explained.
The behaviour isn't the result of valuing copies in other worlds - it is simply valuing your own existence under conditions of uncertainty. The same behaviour would happen just fine in deterministic classical universes with no copying. So, the phenomenon has nothing to do with valuing copies - since it happens just the same regardless of whether the universe makes copies or not.
OK, I'll try again, from the beginning:
What Wei Dai means by "valuing extra copies in other quantum branches" is two things:
Now, there's an argument to be had about whether (2) should be true, even assuming (1), but right now this simply muddies the waters, and it will be much clearer if we concentrate on (1).
So, A valuing his own continued existence means A wanting it to be true that B and C, his possible future selves (in different counterfactual worlds), are both alive. A would not be very happy with B being dead and C being alive, because he would say to himself "that means I have (e.g.) a 1/2 chance of dying". He'd much rather that B and C were both alive.
However, A might think like this: "If the Many Worlds Interpretation is true then it's wrong to say that either B or C but not both will exist. Rather, both of them exist independently in separate universes. Now, what's important to me is that my mind continues in some form. But I don't actually need both B and C for that to happen. So if Roko offered me $100 in exchange for the instantaneous, painless death of B I'd quite happily accept, because from my perspective all that will happen is that I'll receive the $100."
Presumably you disagree with this reasoning, right? Even if MWI is true? Well, the powerful intuition that causes you to disagree is what Wei is talking about. (As he says, giving up that intuition is the position of "quantum immortality".)
The fact that Wei states "the strong version" when "the weak version" would have sufficed is unfortunate. But you will completely miss the point of the debate if you concentrate solely on the difference between the two versions.
Er, what evidence exactly am I supposed to be updating on?
The supplied evidence for 1 ("We value extra copies in other quantum branches") seems feeble. Most people are totally ignorant of the MWI. Most people lived before it was invented. Quantum theory is mostly an irrelevance - as far as people's values goes. If - astonishingly - evidence of wavefunction collapse was ever found, people would carry on caring about things much as before - without any breakdown of morality - despite the loss of practially everything in other worlds. That thought experiment seems to demonstrate that most people care very little about copies of themselves in other worlds - since they would behave much the same if scientists discovered that those worlds did not exist.
Maybe there are somewhere a bunch of people with very odd values, who actually believe that they really do value copies of themselves in other worlds. I can think of at least one fellow who thinks like that - David Pearce. However, if so, this hypothetical silent mass of people have not stood up to be counted here.
Is that even in question? If these values (whatever they are in a given person) can be derived from some higher value, then they may not be arbitrary, but at some point you're either going to find a supergoal that all values derive from, or you're going to find two values that are arbitrary with respect to each other.
Finding the latter case sooner rather than later seems to match how humans really are, so unless you're willing to argue that humans have a supergoal, giving up 3 is a step that you've already taken anyway.