Re: Probability

From: Bruno Marchal <>
Date: Thu, 6 Nov 2008 17:54:05 +0100

On 06 Nov 2008, at 02:37, Thomas Laursen wrote:

> Hi everyone, I am a complete layman but still got the illusion that
> maybe one day I would be able to understand the probability part of MW
> if explained in a simple way. I know it's the most controversal part
> of MW and that there are several competing understandings of
> probability in MW, but still: none of them make sense to me! If every
> line of history is realized then how can any line of history be more
> probable than any other?

Wolf's answer is probably correct, but certainly incomplete. If you
take QM (without collapse) norma distribution and measure can be
extracted from Gleason theorem. Born rule can be deduce from first
person indeterminacy or more politically correct variant through
decison theory (like Deutsch and Wallace). It is a whole field. My
point in this list consists to show that if you assume the mechanist
thesis (like Everett) then even if Deutsch proposal works it is not
enough to justify the probabilities. There is a big work which remains
to be done, but it has the advantage of taking into account the non
communicable part of the experiments (usually known as "the
experience"). But there are more abherant histories to evacuate (like
infinities in field theories).

Anna Wolf's answer can be wrong in case physics is eventually purely
discrete, in which case probabilties should arise from pure relative
proportion based on dircrete relative partitioning of the multiverse.
I think the comp hyp excludes this though, like I think M theory, as
far as I grasp something there, too. Loop gravity, if literally true,
could lead to such ultimate discretization or provide models.

For each position of an electron in your brain there is a (quantum)
computational history going through that state, and probabilities are
eventually all related self-indiscernibility relations (if it is

Bruno Marchal

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Received on Thu Nov 06 2008 - 11:54:27 PST

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