On 31 Aug 2009, at 11:28, marc.geddes wrote:
>
>
>
> On Aug 31, 8:10 pm, Bruno Marchal <marc....domain.name.hidden> wrote:
>> On 31 Aug 2009, at 03:50, marc.geddes wrote:
>
>>
>>> This assumes that qualia are completely determined by the wave
>>> function, which (since Bohm is non-reductionist) I'm sure he'd
>>> dispute. The wave function only predicts physical states, it does
>>> not
>>> neccesserily completely determine higher-level properties such
>>> qualia
>>> (although of course qualia depends on low-level physics). If the
>>> wave
>>> function DID completely determine the qualia, your example would
>>> indeed contradict Bohm - but Bohm already admits he's non-
>>> reductionist.
>>
>> Well, meaning that he is non computationalist. No problem, in free
>> country.
>
> I don't know - does non-reductionist mean non-computationalist? I
> hope not. Non-reductionist just means not all the high-level
> properties of a system are determined by the lower-level properties.
> I'm assuming its still all computational.
>
It has to be non-comp. If not he has to accept that my doppelganger
has experience like you and me, guven that the branch implements the
paralel computation. Bohm is non sensical with comp. Everett is really
just QM + comp, and indeed, it is comp alone (assuming QM is correct).
Now, machanism, after Emil Post-Gödel & Co., can be explained to be
the less reductionist theory possible, as I argue often with John.
>
>>
>>
>>
>>> A weakness of MWI is that it does not describe the reality we
>>> actually
>>> see - additional steps are needed to convert wave function to human
>>> observables - Bohm makes this clear, MWI just disguises it. Even in
>>> MWI, additional unexpected steps (Born probabilities derivation etc)
>>> are needed to convert wave function to what we actually observe.
>>
>> I am not sure. Bohm has to use an unknwown and unspecified (but very
>> vaguely) theory of mind.
>> The MWI has to use only comp (a modern version of a very old theory
>> of
>> mind).
>> (Then I point on the fact that if we take comp seriously the SWE has
>> to be justified from numbers only, but that is nice because it points
>> to a further simplification of the theory).
>
> But the wave function does not describe the reality we actually
> observe -
> that needs additional steps. Bohm just makes his explicit,
> but MWI has them too (needs an additional step to convert wave
> function to Born probabilities, MWI itself doesn't explain why for
> instance we aren't aware of the other branches and don't see
> superpositional states - needs additional theory of mind of some sort
> too).
Everett insists and other have make this more precise that the
probabilities emerge as first person constructs, and comp juutsifies
those first person construct, without assuming QM.
Everett QM confirms comp, up to now.
Everett explains why we don't feel the split, why we cannot see or
interact with the other branches, and provides the correct probability
(quesi directly with Gleason theorem + frequentist proba).
And his the most parcimonious, à-la-Occam theory of nature.
Bohm needs non-comp, and an utterly weird theory of matter, with
hidden particles having necessarily unknown initial condition. All
that for transforming my quantum doppelganger into zombie.
Bohm-De Broglie is a sane reaction in front of Bohr-heisenberg fuzzy
irrealism, or von Neumann-Wigner dualism, but has been made useless
with Everett discovery that we really don't need a wave collapse. You
can derive from the SWE only, why people appears and develop beliefs
in classical reality.
The only (strong) critics you can do to Everett, is that he iis using
comp, and UDA+MGA shows that if QM is empirically correct, then QM has
to be derived purely arithmetically.
Comp makes elemntary Arithmetic the theory of Everything.
>
>
>
>
>>
>>> But MWI has the same problem, it just states it in different
>>> terms, in
>>> MWI all worlds exist, but which one will we actually observe? In
>>> Bohm, only one world is there, but which of the paths in the wave
>>> function is it?
>>
>> Not at all. The question "which world" is reduced to the question
>> "why
>> W" or "Why M" in an WM self-duplication experiment, or to the child
>> question "why do I feel to be me and not my brother". Comp justifies
>> why universal machine have to ask such question, and why they cannot
>> answer them, and why they can explain that such question have no
>> answer when assuming comp.
>> Bohm has to make special an observable (position), to threat away
>> locality, to introduce hidden variables, and a supplementary
>> equation,
>> which describe necessarily hidden things.
>>
>> Bruno
>>
>
> See above, MWI needs supplementary theories too to convert wave
> function into observables (things like procedure for deriving Born
> probabilities etc), in practice position needs to be singled out to
> make measurements.
Not at all. This is the point made clear by Zurek, and the decoherence
theory. Everett theory does not need to sibgle out a base against the
other. The position base singles out itself.
>
> Main problem with Bohm is the non-locality,
and non computationalism. And this makes its theory more reductionist
than computationalism.
> but on the other hand its
> picture of the world is much clearer
I have work on comp to understand what is matter, because the naïve
conception leads to many difficulties, both with QM, but also with
comp, and even by itself (try to define matter without matter, for
example).
The reappartion of particles would be a problem for comp, and a
problem for those who does not believe in particles.
> and doesn't require huge
> quantities of unobservables (alternative universes).
This is a quality of the theory. Not only because it confrims the comp
many dreams, but because a unique physical universe would have been
arguably an ontological aberration.
In any case, Everett is a step by physicist toward comp, and in comp,
at the ontic level, we need the least ontology possible: numbers (with
+ and *). All the rest can be explained, and *is* explained by the
discurses of self-observing universal machine.
> I'd rate the two
> interpretations about equally good (50-50 toss up). Will read your
> links on locality and think over the example more.
Don't hesitate to dig on those issues. No doubt that Bohm provides an
interesting and indeed coherent non local and non computaionalist
theory.
But it looks for me as a sophisticate attempt to dodge the mind-body
problem, and to make very complex, with his non covariant potential,
what is really much more simple (the SWE).
Bruno
http://iridia.ulb.ac.be/~marchal/
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Received on Mon Aug 31 2009 - 15:51:08 PDT