Re: Misc.

From: Marchal <>
Date: Thu Jan 28 03:16:29 1999

Hi James, Hi Everythingers,

>Bruno, I will think about who might translate your fine thesis.

Thank you very much.

>Bruno, you want to say mater is a subset of mind, wheras I said
>mind was a subset of matter. This is a semantic point. I adopt
>your terminology if you prefer.
>Bruno, Russell, Jacques - you correct me where I ask what is
>50% of infinity. OK, I'm wrong on this. But this measure stuff
>and 'instantiating' discussion is a red herring.

I'm afraid I don't agree, but you are very coherent : the question "is
matter a subset of mind or is mind a subset of matter ?" is not a
question of terminology, and this is a reason why the measure stuff
discussion is not a red herring.

May be I should ask you first what you really mean by matter, and what
you mean by mind, but what I want to say is simply this. A priori there
is more computationnal states (and histories) than quantum computationnal
states (and histories).
And you cannot (both with MWI, or mechanism) associate your consciousness
with a machine state (history), you must associate it with with an
infinite set of states (histories). [This is not an obvious statement :
it has been seen independently by myself 1988, Maudlin 1989, and clearly
Hal Finney has seen that point in this very discussion list, it is here
that counterfactuality intervenes]


If you belief that matter is fundamental, and if you belief QM is correct
(all this is a little mysterious for me) then to explain the apparent
working of our prediction (in laboratory and in everyday life) you need
to solve a measure problem. Indeed you must find a (relative) measure on
the accessible quantum histories. That work has been partially completed
by people like Everett, Graham, Gleason, Finkelstein, Hartle, Griffith,
Omnes, etc. The completion, if not the completability of that work is
still controversial.


Now, if you belief mind is fundamental, and if you belief COMP is correct
(where COMP = the belief that you can survive a finitely describable
substitution of yourself), then to explain the apparent working of our
prediction (in laboratory and in everyday life) you need to solve a much
more complex measure problem. Indeed you need to justify both the
classical AND the quantum probabilities from the "mechanist"
indeterminism. That is you must find a (relative) measure on the set of
accessible computationnal histories. And this is a priori a bigger set
than the set of quantum histories. The nice thing is that a success here
would provide an answer to the question "where does the law of physics
come from ?". (This can also be seen as an application of the weak
anthropic principle on number theory).

Put in another way : with QM you have many "worlds", but, a priori, not
as many than with COMP. With COMP I think we must justify, in a purely
non empirical way, why the vast majority of computationnal state we are
living seems to be quantum computationnal state.
And because computer science and number theory are an highly non trivial
corpus of truth, there are hope that such a task can be completed. If the
task is shown logically impossible then COMP would be definitely refuted.
If the task would be completed, then, we get a real and definitive (with
COMP!) theoretical reduction of physics to computer science, including an
explanation why we believe there is a (lawfull) universe.

I feel I agree a lot with Hal Finney and Wei Dai on these questions,
except that I don't attribute any meaning to absolute probability of
being me, only to conditionnal probability of staying me, ... For
exemple, It seems obvious to me that the doomsday argument will not apply
neither with COMP, nor with MWI. Nevertheless, I believe that Leslie
argument can work with NOT-COMP in a "Newtonian and unique" universe.
And it seems to me that I agree with Jacques M on a lot of points, except
I do not understand why he seems so reluctant to Quantum Suicide. With
COMP, even if QM happens to be completely false (I doubt that!), we
still survive "COMP suicide".

A+ Bruno
Received on Thu Jan 28 1999 - 03:16:29 PST

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