Re: all of me or one of me

From: Marchal <marchal.domain.name.hidden>
Date: Tue Apr 13 01:41:10 1999

Gilles H:
>In fact there is no precise definition of what is a macroscopic world in
>MWI. This is one of the major difficulties of the theory; however it is
>logical to consider that two different macroscopic worlds have by
>definition negligible interference terms, which makes the conventional
>interpretation of QM work (reduction of the wave packet). Interference
>terms are important only at the microscopic level.[...]

Bruno M:
OK, but MWI has been invented so that there is no need to distinguish macroscopic from microscopic. This is made still clearer in the decoherence approach.
The term world is also ambiguous. In the MWI if I measure the spin
of an electron which is in a superposition of spin states, I will just put
myself in a macroscopic superposition states, and Everett (+ Hartle, Omnes, etc.) provides a phenomenological explanation why it is difficult to exploit macroscopic interference. But it is really not the MACRO/MICRO distinction which play a role here: it is much more the ISOLATE or CLOSED versus OPEN which makes the difference. Isn't it ?

GH:
>> BM:
>>Remember that with comp we are by definition informatical (in the
>>classical sense) entity, and we are (from a third person point of view)
>>100% exactly duplicable. (In the same sense that you can make *in
>>principle* a perfect copy of the 10E100 first decimal of PI).
>
> GH:
>...but not of PI in a finite time. Of course as we already discussed the
>universe could be discrete. But you cannot make an exact copy of it at its
>finest level (ie Planck scale) with a machine embedded in it.
>The point is that when you say "we are informatical", you probably mean
>that, like a computer, our computational structure can be described with
>much less information than our physical one. That's why we can built
>perfectly reproducible computers, and we can duplicate them with very
>different physical structures.

BM:
That is indeed the point. By the comp hypothesis I mean there is a level
of description such that I survive duplication at that level. I don't know
if comp is true. It is my working hypothesis. What I try to show is that
if comp is correct then, independently of the correctness of QM, we get an
"everything phenomenology (which could very well include "continuous observable" as I was tentatively explaining to Juergen in some post).

GH:
>But it can well be (and it is very probable) that the brain is not like our
>simple computers...

BM:
I agree with "it can well be". I don't think it is very probable.
I mean I don't see why you think it is very probable. The brain is a very hot and stable physical system.
But honestly I don't care. If comp is true, it is a theorem that comp
CAN be consistently asserted false.
I would care if you give me a kind of definite argument that the brain is in some relevant way a continuous non digitalisable object. In that case comp would be proved to be false. If you do that I will believe in physics and abandon the comp approach to the mind-body problem. But today I don't see the slightest evidence in that direction. I take QM as a very strong experimental confirmation of the immaterialist comp hypothesis(°).

GH:
>And in fact the brain is no more
>informatical in the first sense, because it may well be that you need the
>complete description of its physical state. So unlike our artificial
>computers, its evolution is NOT simpler than the evolution of any physical
>system. And if you have to go to the quantum level ,(even worse, to the
>Planck scale!) you are facing a practical impossibility: it is (even in
>principle) impossible to measure the complete quantum state of a single
>system, and a fortiori to reproduce it (just because the complex value
>Psi(x,t) can not be an observable). And as we already discussed you will be
>lead to simulate the whole environment (ie visible Universe) at this level,
>which is also impossible...

BM:
I am sure you are consistent here, and it could be you are correct too,
at least in your conclusion. But the fact that the complete state Psi(x,t)
is not reproducible or measurable is not relevant. The UD* platonistically reproduce it at all digitalisable level by definition; and I have given reason to think that that is enough to explain how the everything feature emerge.

GH:
>As you well know, it is impossible to prepare a macroscopic system in any
>coherent superposition because of the environment induced decoherence. So
>your joke experiment is really impossible (the scientist is either mad or a
>lier!).
>What is possible of course, and very simple, is to prepare you in some
>state like
> (1/sqrt(|a_1|^2 + |a_2|^2)°*
> [a_1*|you in-hell>|world with you in-hell> + a_2*|you in-paradise>|world
>with you in-paradise>]
>
>simply by measuring the spin of a polarized electron on a conveniently
>chosen axis (with relative probability a1/a2) and decide to send you in
>hell or paradize following the result. Of course as your states are
>incoherent you are back to simple probability calculus and the choice is
>obvious.

BM:
OK. But what is your point here ? Globally, we still have a multiplication of our state whith copy of me in hell and copies of me in paradise, in some proportion.

GH:
>What I meant is that if you think you die, your selfishness is useless. You
>only need a minimal amount of altruism to choose B. If you are a pure
>selfish man, you won't care about your choice.

BM:
I don't understand. If I choose A, I expect myself to go in Hell with
high probability. Why shouldn't my "selfish ego" care ?

GH:
>Ok, Bruno may be you would choose B. What about if, despite my promises,
>you are not completely confident in my capability of creating the other
>999999 copies? (I assume of course that once in the box, you are totally
>unaware of what happens really in the other boxes. As is well known, we
>will forget everything in paradise!)

BM:
You are changing the hypothesis of the thought experiment. I suppose here that you are capable of generating the 999999 exact copies.

GH:
>May be this thought experiment is a proof that COMP (understood as the
>possibility of creating an EXACT copy of yourself) is false?

BM:
I have already answer that. The thought experiment shows only that comp is unprovable and unbelievable (this aspect of the thought experiment can be
described with modal axiomatisation of belief,with some reasonable sense of "believable": ...).
You only succeed in convincing me that you don't find comp believable.
But I tell you: no consistent machine can be sure of the correctness of comp. Some machine can bet on it. And my purpose is to explain to "these machines" that if they bet on comp, they must explain the deterministic and local feature of our neighborhood from the high mechanist (UD*-like)
indeterminism and non locality. And that would provide an explanation of the lawfullness of our experiences.

Cheers, Bruno.

(°) To be sure I take the "Q" of QM as an experimental confirmation (not proof!) of comp. To be honest, the "M" of QM remains a rather big mystery.
For a mechanist, the "mechanical action" remains a rather curious think.
With comp the weird aspect of QM appears natural, the non-weird aspect of QM becomes weird!
I am not sure Wei Dai or Schmidhuber "little-program" explanation is enough
here.
I have some hope that Roy Frieden's work will help. But I am afraid that Frieden take "space" and "time" (or space-time) for granted.
Received on Tue Apr 13 1999 - 01:41:10 PDT