On 8/9/2011 7:31 AM, Stathis Papaioannou wrote:
On Tue, Aug 9, 2011 at 12:32 PM, meekerdb<meeke...@verizon.net>  wrote:

That's what I'm questioning.  At what level are "input", "output", and
"behavior" defined?  Does it include a slight twitch of the eye?  a change
in a hormone level in the blood?  a transmission via this nerve instead of
that?  Does the "behavior" only have to be similar enough to fool the
attentive observer, or does it have to be the same all the way down to
neuron, or sub-neuron level.  I'm content to say that fooling the attentive
observer is enough to bet on consciousness.  But to be identical
consciousness you would have to go much lower.  Maybe even to neuron level.
If you substitute a volume of neural tissue with a machine it need
only replicate the I/O behaviour at the interface with the surrounding
neurons in order to leave the person's behaviour unchanged. What goes
on inside the machine may be completely unlike the analogous
physiological process but since overall behaviour is unchanged,

There's the rub. What counts as "overall"? Can I replace one hemisphere of the brain that is functionally identical at its boundaries and guarantee that there is no change in consciousness?

consciousness must be unchanged if the "fading qualia" problem is to
be avoided.

But I'm not concerned about *fading* qualia. I'm asking about *changed* qualia. We certainly have the example of synasthesia in humans which may well be due to a difference that is localized in the brain.

The volume of replaced tissue can be made larger and
larger until the limit is reached where the whole brain is replaced,
leaving only the muscles and sensory organs (and of course these too
can eventually be replaced). If the person's behaviour is unchanged
then his consciousness is also unchanged,

Of course one's consciousness is changed all the time, but perception, experience, and learning. And consequently their behavior is presumably changed too. So when you refer to "the person's behavior" being unchanged you mean something rather vague and fuzzy like "his character". I'm speculating that within that vague domain there might be room for quite a bit of qualia change that would depend on the internal implementation.


even though the artificial
brain functions completely differently to a natural brain. How closely
must the substituted parts follow the I/O behaviour of the original
neurons at the interface? As closely as is followed by normal neural
tissue, which changes from moment to moment correlating with changes
in conscious experience.

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