Bruno Marchal wrote:

> Maudlin build first a digital machine, let us call it M, which do a
> computation PI (Maudlin's name for it) which we suppose does correspond
> to a genuine consciousness experience (for example some remembering of
> the taste of cocoa).

At this point we don't know whether the conscious experience is
supposed to:

1) inhere in the computation independent of physical instantiation
 or
2) inhere in some subset of the physical activity of the machine that
is supposed to be 'relevant' for the computation

It seems that what is intended under 2) must be *any* physical activity
that could be construed as 'implementing' this computation, since
syntactically equivalent hardwares aren't constrained to any particular
set of physical activities.

> Suppose that during the running of that particular computation PI, the
> register r1, ...r67 are never used. Maudlin argue that if consciousness
> is attached to the physical activity relevant for the computation, we
> can retrieve those unused part of the computer, without changing the
> consciousness experience.

OK, under either assumption 1) or 2) above.

> He shows then that he can managed to build a version of M,
> proto-olympia (say) which has almost no physical activity at all when
> he follows the PI computation.

But this will only preserve the conscious experience under the prior
assumption of its invariance to physical activity. If this invariance
is false we have a third possibility:

3) consciousness inheres in *specific* physical activities (and
consequently physically-instantiated comp is merely 'syntactic
simulation')

Under this assumption, changing the physical details of the
implementation might have any arbitrary effect whatsoever on the
original conscious experience.

> Proto-olympia  is *physically* accidentally correct for PI, but no more
> counterfactually correct.

We don't know what effect the lack of counterfactuality would have on
the conscious experience. None, if 3) is correct.

> Then Maudlin reintroduces the unused parts, the Klaras, which
> reintroduces the counterfactual correctness, WITHOUT ADDING any comp
> relevant physical activity (if not, it would mean the level is
> incorrect(*)).

Again, under 3) this wouldn't affect the conscious experience if the
relevant physical invariance is preserved.

So comp + physical supervenience (phys-sup) would force
> us to associate any consciousness experience to any physical processes.

Under 3) it would force us to associate specific conscious experiences
to specific physical processes, at the correct (physical) substitution
level.

> And that would kill comp! So sup-phys -> NOT comp, or equivalently comp
> -> NOT sup-phys.

Under 3) it would kill comp as a theory of the invariance of
consciousness to physical activity. It would be possible for a physical
process that was conscious to be turing-emulable, but for the conscious
experience to be non-invariant to different instantiations of such
emulation. This would follow from the inherence of consciousness in
*specific* physical activities. I'm speaking here of comp as
instantiated in a *physical* machine, and consequently this is no
different to the claim that you can't drive a comp-emulated car down to
the shops (at least not the ones *outside* of the machine). The car you
need for your trip is non-invariant to turing-emulation.

This is essentially the point I attempted to establish in my original
'anti-roadmap' post. Assumption 3 claims that 'conscious' activity must
inhere in specific causal sequences seamlessly spanning the machine and
the world outside it. Without this, it is difficult to see how
'consciousness' could be causally relevant to the intentional
interaction of the machine with its environment.

As conscious machines ourselves we understand very well the difference
between the car we dream of (the 'emulated' Ferrari) and the one we
actually drive (the VW we causally interact with).

David

> Le 03-sept.-06, à 05:07, Stathis Papaioannou a écrit :
>
> > The dynamism part can be provided by a simple physical system such as
> > the idle passage of time.
> > If you allow for parallel processing you don't need much time either.
> > This leads to a situation whereby
> > every computation is implemented by universe with a single electron
> > enduring for a nanosecond, for
> > example. I can't quite see how to get rid of the electron, but
> > Maudlin's and Bruno's conclusion from
> > this seems to be that it is absurd and implies that the mental does
> > not actually supervene on the physical.
>
>
> I think you mix the Mallah Putnam implementation problem, related to
> the idea that any piece of matter could compute, and Maudlin's thought
> experiment showing the incompatibility of the physical supervenience
> thesis (that consciousness should supervene on the physical activity of
> a computer running the computation) and computationalism (that
> consciousness is invariant for a digital functional substitution made
> at some level).
>
> Maudlin build first a digital machine, let us call it M, which do a
> computation PI (Maudlin's name for it) which we suppose does correspond
> to a genuine consciousness experience (for example some remembering of
> the taste of cocoa).
> Suppose that during the running of that particular computation PI, the
> register r1, ...r67 are never used. Maudlin argue that if consciousness
> is attached to the physical activity relevant for the computation, we
> can retrieve those unused part of the computer, without changing the
> consciousness experience.
> He shows then that he can managed to build a version of M,
> proto-olympia (say) which has almost no physical activity at all when
> he follows the PI computation.
> Proto-olympia  is *physically* accidentally correct for PI, but no more
> counterfactually correct.
 So comp + physical supervenience (phys-sup) would force
> us to associate any consciousness experience to any physical processes.
> And that would kill comp! So sup-phys -> NOT comp, or equivalently comp
> -> NOT sup-phys.
> We still have notions of computational supervenience, where persons and
> consciousness are associated to relative number theoretical relations.
>
> Bruno
>
> (*) This explains also why, AT THIS STAGE, to move on a physical
> multiverse would not help (Russell's Standish move), unless it makes US
> non computable, but that would be equivalent to abandoning both comp
> and the quantum (given that quantum mechanics is quantum turing
> emulable).
> 
> http://iridia.ulb.ac.be/~marchal/


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