On 15/07/2016 12:38 am, Bruno Marchal wrote:
On 14 Jul 2016, at 02:11, Bruce Kellett wrote:
On 13/07/2016 11:36 pm, Bruno Marchal wrote:
On 11 Jul 2016, at 13:49, Bruce Kellett wrote:
On 11/07/2016 9:31 pm, Bruno Marchal wrote:
*Holiday Exercise:*
A guy undergoes the Washington Moscow duplication, starting again
from Helsinki.
Then in Moscow, but not in Washington, he (the one in Moscow of
course) undergoes a similar Sidney-Beijing duplication.
I write P(H->M) the probability in H to get M.
In Helsinki, he tries to evaluate his chance to get Sidney.
With one reasoning, he (the H-guy) thinks that P(H-M) = 1/2, and
that P(M-S) = 1/2, and so conclude (multiplication of independent
probability) that P(H-S) = 1/2 * 1/2 = 1/4.
But with another reasoning, he thinks that the duplications give
globally a triplication, leading eventually to a copy in W, a copy
in S and a copy in B, and so, directly conclude P(H-S) = 1/3.
So, is it 1/4 or 1/3 ?
Neither. The probability that the guy starting from Helsinki gets
to Sydney is unity.
Try to convince the guy who gets to Beijing, or the one who stayed
in Washington. He knows that the probability evaluated in Helsinki
was not P(Sidney) = 1.
We start with John Clark in Helsinki, so P(JC ~ H) = 1. By
construction, after the duplication and so on, P(JC ~ W) = P(JC ~ S)
= P(JC ~ B) = 1. (I use '~' as a shorthand for 'in' or 'sees'.)
In the 3-1 view, that is correct.
There is no such thing as "the 3-1 view" distinct from the first person
view. That is just a piece of jargon that you made up to cover the fact
that you have assumed a distinction where none exists.
But in my posts I insist that "W", "M" denotes the experience of
opening the door or the reconstitution box, and writting in the
personal diary which cities is seen. In that case, obviously, P(W),
P(S) and P(B) cannot be all equal to one as W, S and B are
incompatible event.
These are not incompatible events: there are three physical bodies, one
in each city. Your definition of personal identity depends only on
memories (backed up by personal diaries if necessary). With this
definition, and the protocol described, the bodies in W, S, and B are
all the same person. So it is JC who sees W, JC who sees S, and JC who
sees B. They are all the same person, so the correct prediction is that
JC will see all three cities. If you now introduce a difference between
the copies, then they become different persons, and the correct
prediction would be that JC (who sees H) will see no further cities
because he no longer exists.
JC in Helsinki knows the protocol, so he can easily see that these
are the correct probabilities. So, as I said, the probability that
the guy starting from Helsinki gets to Sydney is unity. Any other
interpretation of this scenario involves an implicit appeal to
dualism -- there is "one true JC" that goes through these
duplications, and he can only ever end up in just one place.
Not at all. By comp we agree that they are all the true JC, and that
they all see, taken together, all cities. But the question is about
the personal events lived by the H-guy after he will push the button,
and that makes the events (1p-events) incompatible.
As I said above, the events are not incompatible. You are relying on an
intuition formed in a world without person duplication. Yourclaim that
they are incompatible relies on an implicit dualism -- there is only one
"true" JKC.
As John Clark has correctly pointed out, your intuition and formalism
simply does not work in the presence of person-duplicating machines.
It works very well, but you need to distinguish between the outsider
view: all JC see all cities, and each personal views obtained, which
are incompatible.
You simply borrox John Clark confusion between the 3-1 views and the
1-views.
There is no such thing as the 3-1 view -- that is just a piece of jargon
invented to save your argument. It does not correspond to any true
distinction.
There is no single 1p view -- there are three possible 1p views in
the triplication scenario.
Right. The point is that from the first person perspective, those
1-views are logically incompatible.
No they are not. They all refer to the experience of John Clark, as
defined by you.
So, again, John Clark is right when he says that JC ~ H will see
three cities (W, S, and B) after the experiment is completed.
yes, he is right, but only on the 3-1 view on those 1-views, not on
the 1-views seen by the 1-views, which are incopatible, and which was
what the prediction asked was all about.
See above. I think you have given the correct explanation in one of your
replies to John Clark:
"We have testimony from John Clark that John Clark saw Moscow and not
Washington, and that John Clark saw Washington and not Moscow, and by
computationalism, those experience cannot be lived together, and both
John Clark have differentiated into different person, despite being the
same old Helsinki guy. We have the testimony from both John Clark that
they got one bit of information."
The crucial point in what you say here is that John Clark from Helsinki
has differentiated into different persons. But you then contradict this
by claiming that they are still the same person ("the same old Helsinki
guy"). So your position is clearly incoherent, they can't be both the
same person and yet be different persons.
Actually, the insight that, despite the copying process, different
persons have been created, is the key to unravelling all the confusion
that this issue has generated. It is your base theory of personal
identity that has been shown to be inadequate. The closest continuer
theory, with new persons in the case of ties, is the theory best able to
cope with all of this.
If, as you claim, he will see only one city, you have to have some
dualist 'nut or core' that survives in only one of your copies.
Of course not. Just do the tought experience, and consider all
1-views, as seen from each of them.
Do you agree that if you are promised a cup of coffee in both W and in
M, you can bet in Helsinki that you will get a cup of coffee with
certainty? if yes, it is the same for the question "how many city will
the H-guy seen, from its personal pov, after pushing the button?". The
answer is "only one city", or "I will drink a cup of cofffe in ONE
city with P = one, but I cannot know which one".
Of course, as I said some time ago, the easiest resolution of you
logical conundrums is that JC ~ H does not survive, and that there
are three new persons, one in each city, so the probability that JC
in H will see Sydney is exactly zero.
Then you predict that you will not survive either with a simple
(non-duplicating) teleportation, or with a brain transplant, and we
die ar each instant. That is OK (G and G* concures, but again, it is
in a 3p picture, contradicted by the 1-views, boith intuitively, and
mathematically.
How contradicted mathematically? It is quite a common view among
philosophers of mind that a new person is created in teleportation
(Captain Kirk in 'Star Trek' is killed and replaced by a copy when
teleported). This is not an incoherent view, so you can't just assert
that your view is the only correct one. One can survive very well
without assuming computationalism.
Bruce
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