On Mon, Jul 25, 2011 at 1:48 AM, Craig Weinberg <whatsons...@gmail.com> wrote:
> On Jul 24, 9:52 am, Stathis Papaioannou <stath...@gmail.com> wrote:
>
>> It sounds like you do believe that if the neurons in your visual
>> cortex are replaced you could become blind but not notice that
>> anything has changed and continue to behave normally. If this is so,
>> how do you know that you aren't actually blind now?
>
> The definition of blindness in this context depends on how closely the
> replacement neurons resemble natural neurons and how they are
> integrated with the rest of the brain. There's a lot of possibilities
> for any variation.

The replacement neurons are integrated so that they interact with the
rest of the brain just as normal brain tissue would. An example is the
one you came up with, neurons without their nucleus, which would
function normally at least for a few minutes.

> The visual sense could become dissociated from proprietary
> confirmation so that what you see could feel like you are watching an
> image which is separate from where the rest of you is, so that you
> lose the sense of looking through your own eyes.
>
> You could lose pattern coherence so that even though you can see
> patterns they don't organize themselves into meaningful information
> and there is no difference between seeing a picture and seeing the
> pixels or colored regions that make it up.
>
> You could lose all visual perception but be able to navigate the world
> through a kind of spontaneously available proprioceptive-kinesthetic
> memory which serves the function of vision as far as detecting optical
> phenomenon but does not render it visually. Zombie vision. If anyone
> asks me to read an eye chart, I can read it to them, but not because
> I'm able to see it, just because when I point my eyes over there I
> suddenly know the names of the letters and their positions by heart.
> We don't need awareness to detect optical light, just like we don't
> need awareness to digest food. Replace the visual cortex and maybe you
> just get cognitive results of visual information pre-digested.

If any of those things happened you would say, "Hey, things look
strange!" But you can't say this, because the normal brain tissue,
including the neurons that enable speech, receive normal input from
the replacement neurons. So either everything looks just the same, or
everything looks different but you can't be aware of any difference.

(Please don't say that they *don't* receive normal input, because that
is the entire point of the thought experiment establishing
functionalism!)


-- 
Stathis Papaioannou

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