Le 06-oct.-06, à 19:51, Brent Meeker a écrit :

> Stathis Papaioannou wrote:
>> Bruno Marchal writes:
>>> Le 04-oct.-06, à 14:21, Stathis Papaioannou a écrit :
>>>> Maudlin's example in his paper is rather complicated. If I could
>>>> summarise, he states that one
>>>> of the requirements for a conscious computation is that it not be 
>>>> the
>>>> trivial case of a recording, a
>>>> machine that plays out the same physical motion regardless of input.
>>>> He then proposes a second
>>>> machine next to one which on its own is just a recording, such that
>>>> the second machine comes into
>>>> play and acts on the first machine should inputs be different. The
>>>> system as a whole now handles
>>>> counterfactuals. However, should the counterfactuals not actually
>>>> arise, the second machine just
>>>> sits there inertly next to the first machine. We would now have to 
>>>> say
>>>> that when the first machine
>>>> goes through physical sequence abc on its own, it is just 
>>>> implementing
>>>> a recording and could not
>>>> possibly be conscious, while if it goes through the same sequence 
>>>> abc
>>>> with the second machine sitting
>>>> inertly next to it it is or could be conscious. This would seem to
>>>> contravene the supervenience thesis
>>>> which most computationalists accept: that mental activity supervenes
>>>> on physical activity, and further
>>>> that the same physical activity will give rise to the same mental
>>>> activity. For it seems in the example
>>>> that physical activity is the same in both cases (since the second
>>>> machine does nothing), yet in the
>>>> first case the system cannot be conscious while in the second case 
>>>> it
>>>> can.
>>> This is a nice summary of Maudlin's paper.
>>>> There are several possible responses to the above argument. One is
>>>> that computationalism is wrong.
>>>> Another is that the supervenience thesis is wrong and the mental 
>>>> does
>>>> not supervene on the physical
>>>> (but Bruno would say it supervenes on computation as Platonic 
>>>> object).
>>>> Yet another response is that
>>>> the idea that a recording cannot be conscious is wrong, and the
>>>> relationship between physical activity
>>>> and mental activity can be one->many, allowing that any physical
>>>> process may implement any
>>>> computation including any conscious computation.
>>> Why? The whole point is that consciousness or even just computation
>>> would supervene on *absence" of physical activity.
>>> This is not "on *any* physical activity. I can imagine the quantum
>>> vacuum is "full of computations", but saying consciousness supervene 
>>> on
>>> no physical activity at all is equivalent, keeping the comp 
>>> assumption,
>>> to associate consciousness on the immaterial/mathematical 
>>> computations.
>>> This shows then why we have to explain the relative appearance of the
>>> "physical stuff".
>> It is consistent with Maudlin's paper to say consciousness supervenes 
>> on no
>> physical activity - i.e. on computation as Platonic object - but it 
>> is also consistent
>> to say that it supervenes on a recording, or on any physical 
>> activity, and that
>> perhaps if there were no physical universe with at least a single 
>> quantum state
>> there would be no consciousness. Admittedly the latter is inelegant 
>> compared to
>> the "no physical supervenience" idea, but I can't quite see how to 
>> eliminate it
>> completely.
>> Stathis Papaioannou
> But note that Maudlin's argument depends on being in a classical world.

I don't see this. Maudlin's assumes only that consciousness can be 
attributed to a "classical" computation. Its reasoning would work even 
in the case the brain would be a quantum computer. The reason for that 
is that quantum computations are classically turing emulable.
Church thesis has not been violated by the rise of the quantum turing 
machine, as David Deutsch already explained in his seminal paper on 
quantum computation.

> The quantum
> world in which we live the counterfactuals are always realized with 
> some probability.

And I guess that is why Russell Standish believes that the Maudlin type 
of argument could be just an argument in favor or the (physical) 
multiverse (like UDA could be as well in that case). But this does not 
follow because if the counterfactuals are needed to be simulated, it 
would just mean, assuming comp, that the level of emulation has not 
been correctly chosen. Just redo Maudlin's thought experiment with his 
program PI being a quantum program simulated by a classical Olympia if 
you want to be sure of this.



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