On 6/20/2019 9:09 PM, Bruce Kellett wrote:
On Fri, Jun 21, 2019 at 1:19 PM 'Brent Meeker' via Everything List
<[email protected]
<mailto:[email protected]>> wrote:
On 6/20/2019 5:56 PM, Bruce Kellett wrote:
From: *Bruno Marchal* <[email protected] <mailto:[email protected]>>
I don’t think your refutation of step 3 has been understood by
anyone.
If someone else want to argue that there is no indeterminacy in
the self duplication experience, he is welcome.
I think that some might challenge your interpretation of this
indeterminacy. This might not be exactly JC's objection to step
3, but, to my mind, it is a serious difficulty in its own right.
This comes from a recent podcast of a conversation between Sean
Carroll and David Albert:
https://www.youtube.com/watch?v=AglOFx6eySE
This is a long discussion, and the relevant parts of Albert's
objections to MWI and self-locating uncertainty come towards the end.
The essence of Albert's point is that in the duplication case,
you ask "What is the probability that you will find yourself in
Moscow (resp. Washington)?" Putting aside objections to the
non-specificity of the pronoun 'you', I think your answer is that
the probabilities are 0.5 for either city. Albert points out that
to reach this conclusion, you use some principle of indifference,
or point to some symmetry between the possible outcomes. Using
this symmetry, you claim that the probabilities must be equal,
hence 0.5 for each city. Now, says Albert, there is another
solution that also respects all the symmetries involved, viz., "I
have not idea what the probability is."
You can then easily argue that this is a better solution. Because
the probability 0.5 is not written in the physics of the
situation -- it comes entirely from the classical principle of
indifference. So Albert asks how you are going to verify this
probability experimentally -- as a large N limit, or something
similar. So you repeat the duplication N times on your
participants. i.e. after the original duplication you transport
the subjects back to Helsinki and repeat the duplication to
Washington and Moscow. You end up with 2^N copies, each of which
has a record of the N cities they found themselves in after each
duplication. You now ask each of them their best estimate of the
probabilities for W or M on each duplication. Of course, you then
get all possible answers, from 1/N for M to 1/N for W. Since,
withprobaility one, the will always be someone who found himself
in M each time, and similarly, someone who found himself in W
each time. Plus all other 2^ possible combinations of results.
But most participants will say they were in Washington
approximately N/2 times and Moscow N/2 times, in accordance with a
binomial distribution.
But I am not "most participants". I am just me, only one of me. I
could easily be the guy who sees 100% Moscow.
Not "easily" since seeing only Moscow has probability 1/2^N. And it's
not just you I need to convince. I need to write a paper showing that
my P(M)=P(W)=0.5 theory is supported and the statistics reported by the
participants do exactly that.
Brent
I am the one you have to convince, not those who saw different things.
Bruce
Brent
So who has the correct estimate of the probability for W or M on
each duplication? Clearly, the guy who says "I have no idea" has
a better grasp of the situation than the guy who confidently
claims, "The probability for M is 0.5, and similarly for W."
These probabilities are not written in stone, and any attempt at
an empirical determination of the probability will necessarily
yield all possible results.
This is the core problem with understanding the origin of
probabilities in MWI -- self-locating uncertainty is not good
enough when all outcomes occur with probability one.
Bruce
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