On 12/08/2017 12:23 pm, Stathis Papaioannou wrote:
On 12 August 2017 at 12:12, Bruce Kellett <[email protected]
<mailto:[email protected]>> 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. 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.
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. 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.
The subject directly experiences the details of the experimental
protocol, through hearing or reading about it. All knowledge is 1p;
information from the external world comes to me via my senses and
affects my knowledge.
You render the 1p-3p distinction meaningless.
Bruce
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