On 24 Dec 2011, at 00:24, Russell Standish wrote:

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).

OK.




The argument cannot extend to an apparatus made of extended
multiversal objects, as the "inactive" parts are no longer
inactive.

They are still inactive in your relative branch. if not the level chosen by the doctor is not correct.




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!).

The problem is that to make your argument going through you need, as part as the computation, the activity in the other branches, being not emulable. This for preventing the remebdding of the argulent in a single reality, where Maudlin or MGA works.



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).

It is NOT an additional assumption. Comp says that whatever run my mind is Turing emulable. If you need a multiverse, it has to be Turing emulable by definition of comp.




Then this emulation can be run on a single classically
instantiated computer, and Maudlin's argument applies.

Yes. that's how I argue.



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.

But by definition of comp, and the UDA1-7, consciousness must supervene on that classical instantiated computer.






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.

That's different. This does not entail the reversal physics computer science/number theory. people using the brain in vat still assume that there must be universe and a brain. The brain in a vat, like the old dream argument, shows only that we cannot prove the existence of primitive matter. MGA shows that we cannot use the concept of primitive matter to explain, even just the appearance of primitive matter. It is useless. If matter happens to exist primitively, it would not be a epiphenomenon, as Stephen said, but an epinomenon! Which is a nice jargon for things like "invisible horse".




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".

Actually I do agree with you. but not all members of the jury agreed. To complete the reversal argument logically, that extra-complication seems to be necessary. The point in an argument consists in convincing others, not oneself.




The question of "What breathes the fire into the equations"
(Steven Hawking's question) is simply not meaningful.

Hmm... It is unclear. Wr have still to explain where qualia and primitive matter appearance come from. But we know now. it comes from the internal view that relative numbers can develop on arithmetical truth. That is illustrated in the mathematical part, with the classical theory of knowledge.






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.

It seems to me that those two paragraphs contradict themselves. After MGA we have to drop physical supervenience (called "supervenience" in the philosophy of mind literature). Of course, keeping comp (and abandoning primitive matter and physicalism), we have to use a form of comp-supervenience (and extract matter observation from that). This is what AUDA does in all details (even if it is a toy theology, perhaps). The logic of observation is given by the modality Bp & Dt & p, for p restricted with DU-accessibility (= sigma_1 arithmetical restriction).

Best,

Bruno




Cheers

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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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