On Aug 31, 8:10 pm, Bruno Marchal <marc...@ulb.ac.be> 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.


>
>
>
> > 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).




>
> > 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.

Main problem with Bohm is the non-locality, but on the other hand its
picture of the world is much clearer and doesn't require huge
quantities of unobservables (alternative universes).  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.
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