>From: "Bostrom,N (pg)" <N.Bostrom.domain.name.hidden>
>Jacques Mallah wrote:
> I don't know how closely Nick has followed this list.
>
>Not very closely, unfortunately. Regarding "quantum immortality", my view
>is that if MWI is true, we have to reinterpret "x desires that p" as "x
>desires that p-branches should have a high amplitude". With this simple
>translation, we may continue as if nothing had happened.
So I take it you don't believe in "quantum immortality" or the "RSSA".
>http://www.escribe.com/science/theory/m560.html you say: [snip] You also
>said in that post you weren't sure how to combine the QM probabilities with
>the SSA, but in your last post to RS you seemed reconciled to doing so.
>
>Consider first a partially analogous case, where we assume MWI is false.
>Suppose there are a trillion planets (analogous to different branches on
>the wavefunction), and an Adam and an Eve doing the experiment on each of
>these planets. On the vast majority, no deer turns up, but on one in ten
>thousand planet, the trick works. Now, if Adam knows that this is the
>setup, then he should not think that the trick will work. The reason is
>that the no outsider requirement is not satisfied: to apply SSA with a
>reference class consisting only of the humans living on his planet would be
>wrong. Once we take the reference class to contain all these actual
>observers living on some planet or other, then it is easy to see that
>applying SSA will not give Adam any reason to think that a wounded deer
>will appear.
Right.
>If this is a good analogy to the MWI-case, then the paradox would not arise
>under that assumption. But that is not clear to me at all. For the branches
>of the wavefunction aren't simply so many different actual worlds, but they
>come with a measure. I take it that we need to assume that this measure is
>related to SSA by assigning sample densities to observer-moments that is
>proportional to the measure of the branches on which they are living.
Right.
>This means that observers living on small-measure branches will only weakly
>contribute to the violation of the no outsider requirement; that is, if one
>of the alternative hypotheses under consideration is only true on branches
>which have a small measure, then the no outsider requirement can for all
>practical purposes be regarded as satisfied.
>
>Therefore, if Adam is uncertain whether his world is one where the
>deer-branch has a high or a low amplitude (but thinks that with 99,99%
>probability it has a low amplitude), then when he considers his position,
>he gets reason to think that the deer-branch has high amplitude, since that
>would concentrate a greater sampling weight on observers that are observing
>what Adam observes. (On the other hand, if Adam were certain about the
>shape of the wave function, then the above argument would not show that he
>should think that he will next observe a wounded deer. But why assume that
>Adam knows the shape of the wave function? If he doesn't, then it seems to
>me that my paradox obtains also in the context of the MWI.)
Here's the point you seem to be missing. Suppose, without the MWI, he
would know that on a usual day a deer is 1% likely to turn up. But since
this is not a usual day, but the day that will determine whether he gives
rise to a race, he would think a deer probably will turn up which then means
he won't reproduce. (And not reproducing would give his own case more
effective probability, which is why he thinks it's likely.)
If he believes the MWI however, then he knows there is a branch where a
deer turns up and one where it doesn't. He knows that for a usual day the
effective probability of a deer turning up is about 1%. Since he has no
reason to believe the laws of nature are specially configured to correlate
the amplitude of the wavefunction's branches with his actions (especially
since such correlation would be hard to reconcile with QM), he will still
believe the effective probability of a deer turning up is just 1%.
In addition, in QM there will be many branches even before that day. So
it's also true that branches will exist, with about equal amplitude to his
own where e.g. maybe the weather was different and he chose a different day
to go "deer hunting", where the Earth has two moons, or indeed where the
first man's name was Jack, etc.
These sort or branches do act exactly like regular old alien worlds for
this purpose. Thus even if someone hands him a spin 1/2 particle, state
unknown, he should not consider it just to have some wavefunction which he
could apply the "Adam paradox" to like a classical coin; he must also
consider the already parrallel branches where the equivalent particle has
some other wavefunction, and there are other versions of him there to see
it.
{If he was really ahead of his time, and foreshadowing this list he did
consider the hypothesis that what is called on this list a White Rabbit
exists in the laws of nature, such that the deer and him really are
specially correlated, and if he were to calculate it the way I would, he
would have to consider this possibility to be lower in probability (compared
to the assumption that there is no such WR) by 2^(-l), where l is the length
in bits of the extra information that would need to be encoded into the laws
of physics in order to create such a correlation.}
>I mean that few people would think that SSSA-R stands or falls with MWI.
>Just as it is no good reply to the Adam&Eve paradox that Adam and Eve
>probably never existed, so it also seems to be unsatisfactory to dismiss
>the paradox by saying that it doesn't obtain if MWI happens to be true.
Agreed. As I've already said, the sense of "paradox" is really just a
product of faulty intuition about an atypical case.
> In the 'coin toss' case, the answer is obvious.
>
>Yes, but different answers appear to be obvious to different people.
In this case I really can't imagine why. It's a straightforward
application of Bayesian probability theory.
>>The main motivation is that it avoids certain consequences
>that most people regard as highly counterintuitive and unacceptable.
>
>Well, I've already stated that I regard those consequences as obvious
>and intuitive.
>
>So you accept that Adam should think that a wounded deer will turn up?
>(Let's assume here for the sake of the argument that MWI is false.) You
>would probably be the only person who thinks that that is obvious and
>intuitive.
If the MWI is known to be false, and it is known that there are really
no other planets / universes / intelligent races on that planet / etc., and
if it is known that there will be a one to one correspondence between
whether the wounded deer turns up and whether he gives rise to billions of
descendants, then he should believe that the deer will probably turn up
because that hypothesis predicts his own situation while the hypothesis that
he will reproduce does not.
Of course that's a one time thing. If he tried it too often, then he
certainly would have to reproduce eventually. Knowing that, he wouldn't
even think it would work the first time.
And I do find the premise that he can be certain that no type of MWI can
be true hard to swallow. (As I've said previously on this list, the AUH is
not experimentally falsifiable; as I see it, Occam's razor always favors
it.)
>I would follow any advice I would give to Adam if I were
>in his situation.
>
>It's quite interesting to know that there is someone who would do that. I
>though I would for a while, but after thinking more about this and making
>the situation vivid to my imagination, I came to the conclusion that this
>seemed crazy and that if there were any consistent way of avoiding it, then
>it should be avoided.
Maybe if you keep thinking about it more and more, your beliefs will
swing back again. And if still more, then swing again.
>Of course, everything I say in the thesis is compatible with accepting R=Ru
>(i.e. setting the reference class equal to the class of all observers)
>provided one is also willing to accept the Adam&Eve paradox.
You still haven't presented any way to determine the proper "reference
class". I suggest you use the logical approach: include all observers.
- - - - - - -
Jacques Mallah (jackmallah.domain.name.hidden)
Physicist / Many Worlder / Devil's Advocate
"I know what no one else knows" - 'Runaway Train', Soul Asylum
My URL:
http://hammer.prohosting.com/~mathmind/
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Received on Tue Aug 01 2000 - 17:25:44 PDT