On Fri, Dec 23, 2011 at 11:15:36AM +0100, Bruno Marchal wrote:
> 
> On 22 Dec 2011, at 23:48, Russell Standish wrote:
> 
> >On Thu, Dec 22, 2011 at 03:53:09PM +0100, Bruno Marchal wrote:
> >>
> >>When I say that the movie is thinking, it is in the frame of both
> >>comp *and* the physical supervenience thesis, and it is to get the
> >>reductio ad absurdum.
> >
> >OK - but how does supervenvience cause the reductio in this case? Or
> >is it COMP that causes the reductio? Or must it be the conjunction. I
> >don't understand.
> 
> It comes with the conjunction. The physical activity is shown to be
> arbitrary for the execution of an algorithm. This shows that if we
> keep comp, we cannot associate consciousness with the physical
> activity, but with the "causal" (in the computer science term)
> pattern which makes the computation, at the correct level.

Maudlin's argument demonstrates that in a classical universe, we can
convert any computation into what is essentially a recording + a bunch
of physically inert parts. We reason that disabling, or removing, the physically
inert parts cannot possibly affect the conscious process being
emulated, ie the apparatus with the parts disabled or enabled are
physically equivalent, therefore either the recording is conscious (which is
assumed to be a priori absurd), or supervenience is false
(conscious states differ with no real physical change).

The argument cannot extend to an apparatus made of extended
multiversal objects, as the "inactive" parts are no longer
inactive. But it does require the supervenience to be extended across
multiple multiverse branches in a way that hasn't been made precise (but
presumably not magic!).

Bruno's argument is that the multiverse can be emulated (well this is
an additional assumption to COMP ISTM, but I am happy to grant
it). Then this emulation can be run on a single classically
instantiated computer, and Maudlin's argument applies. But all that
shows is that consciousness cannot supervene on that classically
instantiated computer - it doesn't say anything about supervenience on
the original Multiverse.


> From a logical point of view, we can add a primitive matter as
> necessary, like we can add a God, or a primitive consciousness. What
> the argument shows is that comp makes those things playing no role
> from the first person points of view of the machine. 

This is quite true, but I don't see how that comes from the MGA. It
can be quite easily demonstrated by use of the compiler theorem, or
perhaps more accessibly by "Brain in a Vat" thought experiments -
where it can be shown that it is impossible to know anything about
"primitive" matter - any matter capable of universal computation will do.

And if universal computation is the only necessary property, then we
can just as well use an immaterial system such as PA as our "primitive
matter". The question of "What breathes the fire into the equations"
(Steven Hawking's question) is simply not meaningful.



> So why to add
> something we know nothing about (that kind of gap-explanation
> concept) when they can have no perceptible role. Occam does the
> rest.
> 

Agreed. As I said, I never had a problem with the conclusion, just the
argument.

Also, I am concerned about any disproof of physical supervenience
(regardless of the primitivity question), as supervenience is an
important ingredient for the Anthropic Principle, and ISTM necessary
to avoid the Occam catastrophe.

Cheers

-- 

----------------------------------------------------------------------------
Prof Russell Standish                  Phone 0425 253119 (mobile)
Principal, High Performance Coders
Visiting Professor of Mathematics      hpco...@hpcoders.com.au
University of New South Wales          http://www.hpcoders.com.au
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