Stathis Papaioannou wrote:
> Brent meeker writes:
>
>
>>>Let's not try to define consciousness at all, but agree that we know what it is
>>>from personal experience. Computationalism is the theory that consciousness arises
>>>as a result of computer activity: that our brains are just complex computers, and
>>>in the manner of computers, could be emulated by another computer, so that
>>>computer would experience consciousness in the same way we do. (This theory may be
>>>completely wrong, and perhaps consciousness is due to a substance secreted by a
>>>special group of neurons or some other such non-computational process, but let's
>>>leave that possibility aside for now). What we mean by one computer emulating
>>>another is that there is an isomorphism between the activity of two physical
>>>computers, so that there is a mapping function definable from the states of
>>>computer A to the states of computer B. If this mapping function is fully
>>>specified we can use it practically, for example to run Windows on an x86
>>>processor emulated on a Power PC processor running Mac OS. If you look at the
>>>Power PC processor and the x86 processor running side by side it would be
>>>extremely difficult to see them doing the "same" computation, but according to the
>>>mapping function inherent in the emulation program, they are, and they still would
>>>be a thousand years from now even if the human race is extinct.
>>>
>>>In a similar fashion, there is an isomorphism between a computer and any other
>>>physical system, even if the mapping function is unknown and extremely
>>>complicated.
>>
>>I don't see how there can be an isomorphism between any two systems. Without some
>>structural constraint that seems to throw away the "iso" part and simply leave a
>>morphism.
>
>
> The definition of the structural constraint is part of the isomorphism. Some isomorphisms are
> more economical than others, but there are no God-given isomorphisms or structural constraints.
> The limiting case is simply a lookup table mapping any arbitrary system to another arbitrary
> system. That this is inelegant does not make it invalid.
>
>
>>>That's not very interesting for non-conscious computations, because
>>>they are only useful or meaningful if they can be observed or interact with their
>>>environment. However, a conscious computation is interesting all on its own. It
>>>might have a fuller life if it can interact with other minds, but its meaning is
>>>not contingent on other minds the way a non-conscious computation's is.
>>
>>Empirically, all of the meaning seems to be referred to things outside the
>>computation. So if the conscious computation thinks of the word "chair" it doesn't
>>provide any meaning unless there is a chair - outside the computation. So it is not
>>clear to me that meaning can be supplied "from the inside" in this way. I think this
>>is where Bruno talks about "the required level of substitution" and allows that the
>>level may be the brain at a neural level PLUS all the outside world. So that within
>>this simulation the simulated brain is conscious *relative* to the rest of the
>>simulated world.
>
>
> I don't think it is right to say that the brain is *conscious* relative to the environment. It is
> intelligent relative to the environment, whether that means able to communicate with another
> conscious being or otherwise interacting with the environment in a meaningful way. Although
> we deduce that a being is conscious from its behaviour, and you can only have behaviour
> relative to an environment, only the being itself directly experiences its consciousness. This is
> the 3rd person/ 1st person distinction.
>
>
>>>I know
>>>this because I am conscious, however difficult it may be to actually define that
>>>term.
>>
>>But do you know you would be conscious if you could not interact with the world?
>>That seems doubtful to me. Of course you can close your eyes, stop your ears, etc
>>and still experience consciousness - for a while - but perhaps not indefinitely and
>>maybe not even very long.
>
>
> Maybe there is something about my brain that would render me unconscious if all outside
> input stopped, but that seems to me a contingent fact about brains, like the fact that I
> would be rendered unconscious if my oxygen supply were cut off. A hallucination is defined
> as a perception without a stimulus
Not really; it may just be a perception that doesn't match the stimulus, e.g. a
perception of Christ brought about by hearing certain piece of music.
>and there are millions of people in the world who have
> hallucinations all the time. Sometimes people are so overwhelmed by hallucinatory experiences
> that you could saw their leg off and they don't notice, which is in part how dissociative
> anaesthetics like ketamine work. If you like, you can say that consciousness is maintained by
> one part of the brain interacting with another part of the brain: one part is program, the other
> part data, or one part is computer, the other part environment. The point is, whatever you
> choose to call it, an isolated physical system can experience consciousness.
I won't insist, because you might be right, but I don't think that is proven. It may
be that interaction with the environment is essential to continued consciousness.
>>>The conclusion I therefore draw from computationalism is that every possible
>>>conscious computation is implemented necessarily if any physical process exists.
>>
>>That would seem to require mappings that are not isomorphisms.
>
>
> How do you define the non-isomorphic mappings?
Consider the physical process "tick tock tick tock..." There are only two states so
it can be isomorphic to "1010101..." or "abababa...". But it cannot be isomorphic to
a process "rock scissors paper rock scissors paper..." with three states. There can
be a mapping between them: there can be a mapping between "1" and the content of the
Oxford English Dictionary, but there's no "iso" about the morphism unless there is
some structure that is preserved by the mapping.
>>>This seems to me very close to saying that every conscious computation is
>>>implemented necessarily in Platonia, as the physical reality seems hardly
>>>relevant.
>>
>>It seems to me to be very close to a reductio ad absurdum.
>
>
> Like Bruno, I am not claiming that this is definitely the case, just that it is the case if
> computationalism is true. Several philosophers (eg. Searle) have used the self-evident
> absurdity of the idea as an argument demonstrating that computationalism is false -
> that there is something non-computational about brains and consciousness. I have not
> yet heard an argument that rejects this idea and saves computationalism. Personally,
> I would bet in favour of computationalism being true, but I cannot say that I am sure.
>
> Stathis Papaioannou
I would bet on computationalism too. But I still think the conclusion that every
physical process, even the null one, necessarily implements all possible
consciousness is absurd.
Brent Meeker
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Received on Fri Sep 08 2006 - 00:27:56 PDT