On 12 August 2017 at 12:12, Bruce Kellett <bhkell...@optusnet.com.au> 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.

Stathis Papaioannou

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