On 14 Jul 2016, at 21:36, Brent Meeker wrote:
On 7/14/2016 7:38 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. 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.
But they're not incompatible, they just happen to different
(physical) beings.
But JC agrees that those two different physical being are both the
same person as the Helsinki person. As a person cannot be, in that
protocol, two persons at once from the 1p view, and as the next 1p
view is the object of prediction, the P *are* incompatible.
If not, in QM, we should always predict all outcome at once, which is
clearly refuted by the experience.
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,
But there is no the true JC in a world with duplicating machines or
an Everettian multiverse.
They are all the true JC, with the interpretation of the pronouns on
which everybody has agreed, even ... 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.
I thought the hypothesis was that there is no guy in Helsinki after
he pushes the button?
Then step one is false already. We did agree, even JC, that the W and
M guys are both witnessing that the H-guy did survive the
duplications, which follows from step 1 (surviving a simple
teleportation (annihilation + reconstitution).
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.
I don't see the confusion. There are three 1-views.
But only one cities is seen by all involved 1-view, and that is what
the question was about. So to predict that "I will see all cities" is
a correct 3-1 description, but false for the prediction on the 1-views
seen by each 1-view.
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.
Which proves that, given computationalism and duplicating machines,
there is no such thing as THE first person perspective.
They are all THE first person views, when we interview the resulting
copies. If not, there is no Proba in Everett-QM.
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.
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".
Depends on what you mean by "I". You could also say "I will drink
coffee in both cities with P=1."
That is again the correct 3-1 description, but that is not what is
asked, or it is refuted by all 1-views from their personal pov, and
the H-guy knows that in advance.
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 is it contradicted mathematically.
Because the math, and simple intuition, explains that W, M, S are
incompatible 1-views. Nobody will ever see more than one city with
those protocols. As the H-guy knows that in advance, he knows that he
will survive, from any of its possible accessible 1-views, in one
city, and indeed, both copies will confirm this.
Of course it is contradicted physically, i.e. physical theory is
based on various continuities in space and time.
Looking at the more realistic quantum realization of this
triplication scenario, we can formulate that as follows. We
prepare a spin-half atom with spin along the x-axis, then pass it
through an S-G magnet oriented along the y-axis, getting two
possibilities, which we can call up and down. We then take the up
channel and pass that through a further S-G in the x-direction,
getting two further possibilities of left or right.
Let us perform this experiment many times and count the number of
particles in each of the three possible final states (down, left,
and right). If this is a real laboratory experiment, in which
detection of a particle in any channel leads to irreversible
decoherence and the formation of a separate world containing just
that result, we will find approximately half the particles end up
in the down state, and approximately a quarter in each of the left
and right states. This gives the most reliable estimate of the
real probabilities for the outcome from the given initial state.
If you take the MWI view, then you get one down, one left, and one
right in every run of the experiment, so the probability for each
outcome is unity. In order to get probability of 1/4 for left,
say, you have to detect the absence of a particle in the down
state (so that the particle is certainly in the up state) for
which the probability is 1/2.
Actually, your preferred answer -- that the probability P(H->S) =
1/3,
?
I explained that P = 1/4 is more plausible, unless the guy remains
asleep at the Moscow transit.
is possible only in a fully dualist model. You are essentially
claiming that as the scenario puts John Clark's in all three
cities, it is purely a random chance that selects one of them to
be the "true" John Clark -- a dualist "core" is assigned to one of
these copies purely by chance.
On the contrary, I have always insisted that all three of them are
equally real and conscious, and equal in the right to claim they
were the H-guy.
But just put yourself in their places: they all feel like if a
selection has occurred. The same when you measure a spin in QM, the
indterminacy comes from the realisation of all the alternatives,
without invoking dualism, like in Copenhagen.
This is the problem with probabilities in the MWI -- how do you
interpret probabilities when all possible outcomes occur with
probability one?
The probabilities concern the relative first person experiences.
Computationalism guaranties that there will be only one outcome.
You are simply talking nonsense, here. "Relative first person
experiences"? Relative to what?
In our protocol, relative of being the helsinki guy.
The scenario, and computationalism guarantees that there will be
all three outcomes.
In the 3-1 view, that is correct, but like John Clark, you dismiss
that the question is about the experience which will be left, as
seen by the experiencer himself (herself). Those are incompatible
alternatives. Nobody will live those experiences at once. each of
them will feel like being in once city, with honorable
doppelgangers in the other city or cities.
If there is only one "1p" experience, then that can only be chosen
dualistically.
Not at all. the beauty of computtaionalism, is that it explains why
we feel like there is a dualism, but we know that it is an illusion
due to the duplication of the diaries, which cannot contains
statements like "I open the door and saw W and M blurred into one
experience". for that, you need to add telepathy and spooky action
at a distance.
If there is duplication (triplication) then your intuitions break
down. I have to say it -- John Clark has been right all along.
John Clark has confused the 1-views and the 3-1-views all along,
and you just borrow its confusion, I'm afraid.
That confusion is of course the confusion that if we pursue lead to
the elimination of the 1-view, like with the eliminativist
materialist (Churchland, Dennett, ...), which is just the
aristotelian technic to put the mind-body problem under the rug,
since a long time (but not done by Aristotle Himself, only by the
non rigorous successors.
Not the elimination, but the recognition that it is not a unique
thing or substance.
But that is enough to get the subjective, 1p, indeterminacy.
And if it can be duplicated then it no long makes sense to talk
about THE first person.
There is THE first person view in W, which is the one lived by the guy
in front of me when I do the verification in M, and there is THE first
person view in M, which is the one lived by the guy in front of me
when I do the verification in W. For both H-guys (the HM-guy and the
HW guy)it is THE view they got after pushing the button, and that is
THE 1-view we tried to predict in Helsinki. The computationalist knows
in advance that he remains unique from its personal 1p view in such
experience (by comput.)
Bruno
Brent
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