On 12 Aug 2017, at 04:12, Bruce Kellett wrote:
On 12/08/2017 3:22 am, Bruno Marchal wrote:
On 11 Aug 2017, at 13:40, Bruce Kellett wrote:
Are you telling us that P(W) ≠ P(M) ≠ 1/2. What do *you*
expect when pushing the button in Helsinki?
I expect to die, to be 'cut', according to the protocol. The guys
in W and M are two new persons, and neither was around in H to
make any prediction whatsoever.
Fair enough.
You think the digital mechanism thesis is wrong.
Correct.
There is a fundamental problem with your person-duplication thought
experiments. This is that the way in which you interpret the
scenario inherently involves an irreducible 1p-3p confusion. The
first person (1p) concerns only things that the person can
experience directly for himself. It cannot, therefore, involve
things that he is told by other people, because such things are
necessarily third person (3p) knowledge -- knowledge which he does
not have by direct personal experience. So our subject does not know
the protocol of the thought experiment from direct experience (he
has only been told about it, 3p). When he presses the button in the
machine, he can have no 1p expectations about what will happen
(because he has not yet experienced it). He presses the button in
the spirit of pure experimental enquiry -- "what will happen if I do
this?" His prior probability for any particular outcome is zero.
That is just plain false. The guy in Helsinki knows the protocol, and
he assumes Mechanism. So he knows that P(W) = P(M) , and that P(W) ≠
0, and P(M) ≠ 0, and P(X) for any X different from W and M is equal
to 0.
So when he presses the button in Helsinki, and opens the door to
find himself in Moscow, he will say, "WTF!". In particular, he will
not have gained any 1p knowledge of duplication. In fact, he is for
ever barred from any such knowledge.
Yes, that is the 3p/1p confusion that John Clark is doing. He told me
that the guy in Moscow says "I knew it", or I predicted it, by saying
that P(W & M) = 1.
You try to help John C., but you contradict his "theory" (which is
indeed based on the 1p/3p confusion).
If he repeats the experiment many times, he will simply see his
experiences as irreducibly random between M and W, with some
probability that he can estimate by keeping records over a period of
time. If you take the strict 1p view of the thought experiment, the
parallel with the early development of QM is more evident. In QM, no-
one has the 3p knowledge that all possible outcomes are realized (in
different worlds).
So, before pressing the button in H, his prior probabilities are
p(M) = p(W) = 0, with probably, p(H) = 1.
What?
(I recall that in H the person is annihilated).
On the other hand, if you allow 3p knowledge of the protocol to
influence his estimation of probabilities before the experiment, you
can't rule out 3p knowledge that he can gain at any time after
pressing the button. In which case, the 1p-3p confusion is complete,
p(M) = p(W) = 1, and he can expect to see both cities. In that case,
the pure 1p view becomes irrelevant.
W and M, as they have defined (they concern the experience of opening
a door and describing which city is seen) are incompatible experience,
and the protocol entails that P(W) = P(M). If P(M) = P(W) = 1, you get
a probability equal to 2. With the UD, eventually we will have a
notion of credibility in place of probability, but this does not
happen in the self-duplication protocol. You just cannot have P(M), or
P(W) = 1, because that is refuted directly by both copies, when asked
about their first person experience.
Bruno
Bruce
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