On 16/07/2016 4:28 pm, Bruno Marchal wrote:
On 15 Jul 2016, at 02:07, Bruce Kellett wrote:
On 15/07/2016 9:42 am, Jason Resch wrote:
I printed the following "Duplicate Questionnaire" and gave one to
both John-Washington, and John-Moscow. The questionnaires each had 8
questions:
1. What city did you last recall being in?
2. How many cities do you see now?
3. What is the name of the city you see before you?
4. True/False: You see two cities right now:
5. True/False: The prediction that you see Washington was:
6. True/False: The prediction that you see Moscow was:
7. True/False: The prediction that you see Washington and Moscow was:
8. True/False: The prediction that you see Washington or Moscow was:
When I gave the questionnaire to John-Washington, he filled out the
following answers (in bold):
1. What city did you last recall being in? *Helsinki*
2. How many cities do you see now? *One*
3. What is the name of the city you see before you? *Washington*
4. True/False: You see two cities right now: *False*
5. True/False: The prediction that you see Washington was: *True*
6. True/False: The prediction that you see Moscow was: *False*
7. True/False: The prediction that you see Washington and Moscow
was: *False*
8. True/False: The prediction that you see Washington or Moscow was:
*True*
When I gave the questionnaire to John-Moscow, he filled out the
following answers (in bold):
1. What city did you last recall being in? *Helsinki*
2. How many cities do you see now? *One*
3. What is the name of the city you see before you? *Moscow*
4. True/False: You see two cities right now: *False*
5. True/False: The prediction that you see Washington was: *False*
6. True/False: The prediction that you see Moscow was: *True*
7. True/False: The prediction that you see Washington and Moscow
was: *False*
8. True/False: The prediction that you see Washington or Moscow was:
*True*
Both Johns expressed deep regret over insulting people on the
Everything list, most especially Bruno. It turned out neither
John-Washington's, nor John-Moscow's prediction that they would see
both cities was true from their own first person points of view.
But you have introduced a distinction between John-W and John-M that
is not present in the original protocol. Remember that the criterion
of personal identity you are working with is based on person memories
(verified by a personal diary if necessary). Both copies of John have
these memories and these diaries, so they both have equal claims to
be John. "John", as this duplicated person, predicts with certainty
that he will see W, and that he will see M, so he predicts that he
will see both cities.
Yes, but only one in all 1p views accessible, and the question is on
the future 1p view, not on the 3-1 views, for the same reason that
when we look at 1/sqrt(2)(up + down) in the {up, down} base we can
predict with certainty that we will see either up, OR down and never
both at once.
I have said several times that probability is a problem for the
Everettian or MWI view. This is not a problem of defining a measure over
a possible infinite number of worlds -- though that is certainly a
problem that has not really been solved -- but the main difficulty lies
in the observation that probability makes little sense in a situation in
which everything possible does happen. So there is no workable notion of
probability in the Everettian multiverse.
Standard quantum mechanics gets around this in a fairly straightforward
way: the "other worlds" in which alternative outcomes occur are
disjoint, with no possible future interaction with the world in which we
find ourselves. Such alternative outcomes can thus be safely ignored
because they can have no possible effect on the observer or on his
future evolution. Decoherence ,and the irreversibility of completed
experimental outcomes, thus reduce QM to an effective collapse situation
-- there is no physical collapse, but FAPP the other worlds have
vanished from existence.
The fact that this appears odd is that our conventional intuition is
essentially dualist -- we think that there is a central core that is
the "real me" that gives me my continuing sense of personal identity.
This intuition breaks down when you have duplication of persons.
Then computationalism, and Everett QM breaks down. Computationalism
guaranties that whoever you will become, it is lived and felt as one
unique person in one city, or you bring some telepathy of a kind not
possible with computationalism with the protocol discussed.
Everett breaks down only if you try and imagine that the observer
actually lives in the multiverse. But he does not -- the observer only
ever observes one world. He might be uncertain as to which world he will
inhabit in the future (which experimental outcome he will observe), but
this does not introduce the paradoxes of person duplication in one world.
As you say in another post, computationalism depends on the breakdown of
transitivity for personal identity: M is the same as H; W is the same as
H; but M is not the same as W. Given this, you have all sorts of
problems with the nature of personal identity -- maybe it is not a modal
concept! I will talk more about this in reply to your other post.
Bruce
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