On Thu, Jul 28, 2011 at 5:04 AM, Craig Weinberg <whatsons...@gmail.com> wrote:
> On Jul 27, 7:37 am, Stathis Papaioannou <stath...@gmail.com> wrote:
>> On Tue, Jul 26, 2011 at 11:29 PM, Craig Weinberg <whatsons...@gmail.com> 
>> wrote:
>
>> But you must believe that your vision is normal, because the parts of
>> your brain responsible for formulating beliefs and expressing them are
>> receiving exactly the same inputs as they would normally receive.
>
> I'm saying that they would not receive the same inputs just because
> what we see on an MRI looks the same to us. That may not be the whole
> picture. It may not even be half of the picture. If you replace a room
> full of people dancing with audioanimatronic mannequins doing the
> exact same dance, the mannequins don't start dancing by themselves
> because they feel like dancing.

It is only necessary that the artificial neurons look the same to
other neurons, not that they look the same on an MRI since neurons
don't use MRI machines. In the dancing example, it is only necessary
that the artificial dancers look the same to the other dancers: the
dance will then continue as before. If the artificial dancers lack
blood, for example, that would make no difference unless the dance
required bleeding. And if the dance did require bleeding then the
artificial dancers could be given artificial blood. You need only do
enough to fool the other participants.

>> As I
>> keep repeating, that is the entire point of the experiment. The
>> replacement neurons function the same,
>
> As I keep repeating, we cannot assume that it is possible for anything
> other than neurons to function the same as neurons. I believe that
> they wouldn't have to be identical, but my hunch is that the emulation
> would be severely lacking without chemical and biological levels being
> represented.

Firstly, the laws of physics appear to be computable, which would mean
that it is just a technical problem to simulate any physical system.
You model the biochemistry of a cell and connect the model to suitable
I/O devices interfacing with sensory organs, muscle and other neurons.
Only if you claim that there is something fundamentally uncomputable
in the behaviour of biological systems would this be impossible. Roger
Penrose claims just that - that cells utilise as yet unknown
uncomputable physics - but there is no evidence for this.

Secondly, it is beside the point for the purposes of the present
argument whether in fact the behaviour of a neuron could be adequately
simulated. The point is that IF the behaviour could be simulated THEN
the consciousness would necessarily follow. Consciousness is not
something that can be separated from behaviour, for if it could it
would lead to the absurdity of a partial zombie.

> except they are assumed to lack
>> consciousness because they lack some vital component. Is it possible
>> to make such neurons? I don't believe it is possible as it would lead
>> to the absurdity of partial zombies.
>
> But there are partial zombies already. That's why people drink coffee.

A partial zombie would lack a subset of consciousness but behave
normally and be unaware that anything was different. If your visual
cortex were zombified by being replaced with neurons that functioned
normally but lacked consciousness, you would go blind but you would
behave normally, declare that you had normal vision and believe that
you had normal vision.

>> The claim is that in order to preserve consciousness it is only
>> necessary to replicate the externally observable behaviour of neural
>> tissue.
>
> Observable to who?

The replaced neurons must behave normally in their interaction with
other neurons. Their structure could thus be different as long as this
difference does not affect their function. For example, rather than
making proteins on ribosomes they could be made on tiny solid phase
peptide synthesizers. It would be technically different but this is a
thought experiment: we can imagine that the artificial neurons are
made by engineers with godlike abilities.


-- 
Stathis Papaioannou

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