Bruno Marchal writes:
> Le 07-janv.-07, à 19:21, Brent Meeker a écrit :
>
> > And does it even have to be very good? Suppose it made a sloppy copy
> > of me that left out 90% of my memories - would it still be "me"? How
> > much fidelity is required for Bruno's argument? I think not much.
>
>
> The argument does not depend at all of the level of fidelity. Indeed I
> make clear (as much as possible) that comp is equivalent to the belief
> there is a level of substitution of myself (3-person) such that I
> (1-person) survive a functional substitution done at that level. Then I
> show no machine can know what is her level of substitution (and thus
> has to bet or guess about it).
>
> This is also the reason why comp is not jeopardized by the idea that
> the environment is needed: just put the environment in the definition
> of my "generalized brain".
>
> Imagine someone who say that his brain is the entire galaxy, described
> at the level of all interacting quantum strings. This can be captured
> by giant (to say the least) but finite, rational complex matrices. Of
> course the thought experiment with the "yes doctor" will look very
> non-realist, but *in fine*, all what is needed (for the reversal) is
> that the Universal Dovetailer get through the state of my generalized
> brain, and the UD will get it even if my "state" is the state of the
> whole galaxy, or more.
>
> If it happens that my state is the galaxy state AND that the galaxy
> state cannot be captured in a finite ('even giant) way(*), then we are
> just out of the scope of the comp- reasoning. This is possible because
> comp may be wrong.
This is right, and it is perhaps a consequence of comp that computationalists
did not brgain on. If the functional equivalent of my brain has to interact with
the environment in the same way that I do then that puts a constraint what sort
of machine it can be, as well as necessitating of course that it be an actual
physical machine. For example, if as part of asserting my status as a conscious
being I decide to lift my hand in the air when I see a red ball, then my
functional replacement must (at least) have photoreceptors which send a signal
to a central processor which then sends a motor signal to its hand. If it fails the
red ball test, then it isn't functionally equivalent to me.
However, what if you put the red ball, the hand and the whole environment inside
the central processor? You program in data which tells it is seeing a red ball, it sends
a signal to what it thinks is its hand, and it receives visual and proprioceptive data
telling it it has successfully raised the hand. Given that this self-contained machine
was derived from a known computer architecture with known sensors and effectors,
we would know what it was thinking by eavesdropping on its internal processes. But
if we didn't have this knowledge, is there any way, even in theory, that we could
figure it out? The answer in general is "no": without benefit of environmental interaction,
or an instruction manual, there is no way to assign meaning to the workings of a machine
and there is no way to know anything about its consciousness. The corollary of this is
that under the right interpretation a machine could have any meaning or any
consciousness.
You can't avoid the above problem without making changes to (standard) computationalism.
You can drop computationalism altogether and say that the brain + environment is not
Turing emulable. Or, as Bruno has suggested, you can keep computationalism and drop the
physical supervenience criterion.
Stathis Papaioannou
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Received on Mon Jan 08 2007 - 08:37:08 PST