Stathis Papaioannou wrote:
>On 2/20/07, Jesse Mazer <[EMAIL PROTECTED]> wrote:
> >
> >
> > >I would bet on functionalism as the correct theory of mind for various
> > >reasons, but I don't see that there is anything illogical the 
> > >that consciousness is substrate-dependent. Let's say that when you rub
> > two
> > >carbon atoms together they have a scratchy experience, whereas when you
> > rub
> > >two silicon atoms together they have a squirmy experience. This could
> > just
> > >be a mundane fact about the universe, no more mysterious than any other
> > >basic physical fact.  What is illogical, however, is the "no causal
> > effect"
> > >criterion if this is called epiphenomenalism. If the effect is purely 
> > >necessarily on first person experience, it's no less an effect; we 
> > >not
> > >notice if the carbon atoms were zombified, but the carbon atoms would
> > >certainly notice. I think it all comes down to the deep-seated and very
> > >obviously wrong idea that only third person empirical data is genuine
> > >empirical data. It is a legitimate concern of science that data should 
> > >verifiable and experiments repeatable, but it's taking it a bit far to
> > >conclude from this that we are therefore all zombies.
> > >
> > >Stathis Papaioannou
> >
> > One major argument against the idea that qualia and/or consciousness 
> > be substrate-dependent is what philosopher David Chalmers refers to as 
> > "dancing qualia" and "fading qualia" arguments, which you can read more
> > about at . As a thought-experiment,
> > imagine gradually replacing neurons in my brain with functionally
> > identical
> > devices whose physical construction was quite different from neurons
> > (silicon chips emulating the input and output of the neurons they
> > replaced,
> > perhaps). If one believes that this substrate is associated with either
> > different qualia or absent qualia, then as one gradually replaces more 
> > more of my brain, they'll either have to be a sudden discontinuous 
> > (and it seems implausible that the replacement of a single neuron would
> > cause such a radical change) or else a gradual shift or fade-out of the
> > qualia my brain experiences...but if I were noticing such a shift or
> > fade-out, I would expect to be able to comment on it, and yet the
> > assumption
> > that the new parts are functionally identical means my behavior should 
> > indistinguishable from what it would be if my neurons were left alone. 
> > if we suppose that I might be having panicked thoughts about a change in
> > my
> > perceptions yet find that my voice and body are acting as if nothing is
> > wrong, and there is no neural activity associated with these panicked
> > thoughts, then there would have to be a radical disconnect between
> > subjective experiences and physical activity in my brain, which would
> > contradict the assumption of supervenience (see
> > ) and lead to
> > the
> > possibility of radical mind/body disconnects like rocks and trees having
> > complex thoughts and experiences that have nothing to do with any 
> > activity within them.
> >
> > Jesse
>  It's a persuasive argument, but I can think of a mechanism whereby your
>qualia can fade away and you wouldn't notice. In some cases of cortical
>blindness, in which the visual cortex is damaged but the rest of the visual
>pathways intact, patients insist that they are not blind and come up with
>explanations as to why they fall over and walk into things, eg. they accuse
>people of putting obstacles in their way while their back is turned. This
>isn't just denial because it is specific to cortical lesions, not blindness
>due to other reasons. If these patients had advanced cyborg implants they
>could presumably convince the world, and be convinced themselves, that 
>visual perception had not suffered when in fact they can't see a thing.
>Perhaps gradual cyborgisation of the brain as per Hans Moravec would lead 
>a similar, gradual fading of thoughts and perceptions; the external 
>would not notice any change and the subject would not notice any change
>either, until he was dead, replaced by a zombie.
>Stathis Papaioannou

That's an interesting analogy, but it seems to me there's an important 
difference between this real case and the hypothetical fading qualia case 
since presumably the brain activity associated with inventing false visual 
sensations is different from the activity associated with visual sensations 
that are based on actual signals from the optic nerve. Additionally, we'd 
still assume it's true that their reports of what they are seeing match the 
visual qualia they are having, even if these visual qualia have no relation 
to the outside world as in dreams or hallucinations. In the case of 
replacing the visual cortex with functionally identical computer chips, the 
activity in the remainder of the brain would be identical to what it would 
be if the visual cortex were left intact, and if the "fading qualia" picture 
were true they'd be continuing to report visual sensations even when they 
weren't having any whatsoever, not even hallucinatory ones. So basically 
you'd be forced to conclude that even in normal people with unmodified 
brains, the fact that we talk about having various sensations and 
perceptions has absolutely nothing to do with the fact that we actually do 
have them. Of course anyone who sees qualia as "epiphenomal", and who sees 
physically identical zombies as a logical possibility, will say that our 
qualia don't have any *causal* effect on the physical brain, but they still 
usually assume some set of "psychophysical laws" which insure that the 
association between physical activity in the brain and qualia is a sensible 
one (somewhat akin to Leibniz's 'pre-established harmony' solution to the 
mind-body problem--see 
), so that  the causal relation between the brain processing visual 
information and the brain creating verbal descriptions of what one is seeing 
is mirrored by a relation between visual qualia and the qualia associated 
with verbal thoughts about what one is seeing. If you don't assume such 
"sensible" psychophysical laws, then you have no basis for believing even 
now that you should trust any verbal thoughts about what you are seeing. I 
might say to myself that I can trust my visual experiences themselves before 
I translate them into verbal terms, but the very act of *saying* that to 
myself seems to undermine it since I can't be sure if the words 'visual 
experiences' even refer to anything--a bizarre paradoxical situation.


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