Le 08-janv.-07, à 14:27, Stathis Papaioannou a écrit :

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.

Up to here I do agree.

The corollary of this is that under the right interpretation a machine could have any meaning or any consciousness.

I don't think that this corollary follows. Unless you are postulating a "physical world" having some special property (and then the question is: what are your axiom for that physical realm, and where does those axioms come from). Even in classical physics, where a point can move along "all real numbers", I don't see any reason such move can represent any computation. Of course I consider a computation as being something non physical, and essentially discrete, at the start. The physical and continuous aspect comes from the fact that any computation is "embedded" into an infinity of "parallel" computations (those generated by the UD). Brent says that the "evil problem" is a problem only for those who postulate an omniscient and omnipotent good god. I believe that somehow a large part of the "mind/body" problem comes from our (instinctive) assumption of a basic (primitive) physical reality.

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.

I am OK with this ('course).



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