Stathis Good point about downstream report of perception. It prompts me to realise that functional equivalence is a matter of degree or context. You can swap a digital for an analogue waveform generator with the same spec: they are functionally equivalent for that purpose. If you convert the digital generator to produce noise, however, the best software can do is produce pseudo-random sequences (ones that repeat) so the output only looks like noise whereas an analogue noise generator produces a genuine random waveform. Thus, in this application the devices are not functionally equivalent. Likewise, it depends on the purpose whether a digital artifical neuron (DAN) is functionally equivalent to an analogue one (AAN). Swapping out a biological peripheral neuron for either type should be ok - your arm still moves, for example, whichever type of neuron innervates the muscles. My assertion is that the equivalence fails when it comes to consciousness. Taking this argument to the neuron replacement thought experiment, as you replace central neurons with AANs, nothing happens, but the result is loss of qualia if you use DANs. At the end of the replacement In the latter case it seems reasonable that there would be functionality along the lines of blindsight and automatism. cheers Richard

john locke wrote: quote-- This process is known clinically, in a slightly different context, as "blind sight". So I see no problem with the possibility Brent's suggestion. We now know that the brain mechanisms generating visually obtained knowledge are different from the brain mechanisms involved in creating sensa. As Edmond Wright says "Sensations are phenomenologically but not epistemologically involved in visual perception." --endquote In blindsight the subject believes that he lacks visual perception, but in fact responds appropriately to visual stimuli as if he were not blind. In Anton's Syndrome the subject is blind, staggering about into things, but believes that he can see and confabulates when asked what he can see. The case I have proposed, where the subject has his visual cortex replaced by computer chip equivalents that have the same I/O behaviour but lack qualia, is different again. The subject believes that he can see *and* behaves as if he can see, but is in fact blind. This is not only something that never occurs in real clinical situations but also very difficult to conceptualise. How would you know, for example, if every Tuesday you become completely blind, but have never noticed that you are blind yourself and display no behaviour that would lead an external observer to think that you are blind? It would make the term "perception" quite meaningless. quote-- p.s. no neurons "possess" qualia. Neurons are part of an TV-like representational mechanism that ultimately generates qualia. Qualia exist in the visual field in phenomenal consciousness. Only if you first assume (without proof) that the Identity Theory is true can you claim that qualia exist in neurons. --endquote The components of a TV do not "possess" moving images, but functioning together as a system they give rise to the images. Only if you assume that moving images are identical to the TV components can you assume that the images reside in them.

john locke, My view is that qualia are caused by brain activity in the same way as rolling is caused by the interaction between a ball and an inclined plane. There is no soul and there is no spirit of rolling. But if you want to say that qualia and rolling are emergent properties, or even separate ontological entities, then that's OK.

Comment on Stathis's following comment on Brent "So with the artificial sensory neurons you could be completely blind, but declare that you see the strawberries, describe the strawberries accurately, and be able to pick the strawberries. Do you see how that last sentence *has* to be true if the artificial neurons reproduce the I/O behaviour of the biological neurons but lack qualia?" This process is known clinically, in a slightly different context, as "blind sight". So I see no problem with the possibility Brent's suggestion. We now know that the brain mechanisms generating visually obtained knowledge are different from the brain mechanisms involved in creating sensa. As Edmond Wright says "Sensations are phenomenologically but not epistemologically involved in visual perception." p.s. no neurons "possess" qualia. Neurons are part of an TV-like representational mechanism that ultimately generates qualia. Qualia exist in the visual field in phenomenal consciousness. Only if you first assume (without proof) that the Identity Theory is true can you claim that qualia exist in neurons.

Brent, It is true that a whole system of neurons is needed to perceive red, but within this system there are sensory neurons and motor neurons. The motor neurons don't perceive colour, but rely on information from the sensory neurons. Now, you are proposing that the artificial neurons might cause the motor neurons to behave normally (since they present them with the same inputs) but *without* conveying the information about qualia, since they don't have any. So with the artificial sensory neurons you could be completely blind, but declare that you see the strawberries, describe the strawberries accurately, and be able to pick the strawberries. Do you see how that last sentence *has* to be true if the artificial neurons reproduce the I/O behaviour of the biological neurons but lack qualia?

Stathis You claim "Whether we say that consciousness supervenes on brain activity or that consciousness is identical with brain activity is one of those terminological discussions that philosophers are fond of but which makes no material difference to the question at issue:" This is not a 'terminological" issue —i.e. an argument about words—but it is a matter of fact. The two competing claims (1) that neuronal events and sensa (qualia) are identical and (2) that they are not identical but are ontologically separate and interact causally, is an argument about the nature of the world, not about the meaning of "identity" and "causality". The questions raised in this camp, about artificial neurons wired into the brain, are subserviant to the solution of the major problem of the nature of the relationship between ordinary neurons and sensa (qualia). If these are not identical then we have to be clear about how they are not identical and about how they interact. We cannot merely assume, without demonstration, that the Identity Theory is true.

John said: Then, if the neurons are replaced with silicon chips, which can process their inputs in the same functional way as the neurons they replace do, it is purely an empirical matter of fact whether P can, or cannot, also interact with these silicon chips in the same way that P normally interacts with NCCs. And I think Stathis said the same thing with: If artificial neurons in your visual cortex produce the same electrical output (while lacking qualia), then as far as your motor neurons are concerned you have seen the strawberries as per usual. And this is where I see a fallacy. First off, I doubt it is a single neuron that is responsible for an action that initiates the picking of the strawberry, or an attempt to describe what red is like. The most up stream set of output signals that are controlling the picking of the strawberry are dependent on the system that knows what red is like, and what green is like, and only thereby knows where the strawberry is within the field of leaves. Though some system, that represents the knowledge that is red and green with something different, could reproduce identical behavior of selecting the strawberry, It would not be subjectively 'like' it, and it could not reproduce the same behavior of attempting to describe what the red and green are phenomenally like, and how they are different. At least that is without lying about it. And if we can eff the ineffable, we could thereby detect that it was lying - that the neural correlate that always and only always has the red qualia, was not present, but something different, entirely. If it was a lying system, it would certainly be much more complex, in its attempt to reproduce what it was phenomenally like with something that was different (inverted qualia) or entirely absent (zombie). This is what I attempted to describe in the [http://canonizer.com/topic.asp/79/2 Transmigration Fallacy camp], but I must not have done a very good job? This discussion is certainly helping me clarify these thoughts, helping me to know the best language to use, and I very much appreciate it. Brent

john locke, Whether we say that consciousness supervenes on brain activity or that consciousness is identical with brain activity is one of those terminological discussions that philosophers are fond of but which makes no material difference to the question at issue: if biological neurons are replaced with electronic analogues that have the same I/O behaviour, will you have the same qualia or won't you? My contention is that IF the I/O behaviour of the artificial neurons is the same THEN the qualia will also be the same. The alternative to this is that the motor neurons would somehow know that the qualia had changed and behave differently even though their inputs from the artificial sensory neurons are exactly the same as they would have been from the biological neurons, which is impossible unless we allow magic. You might say that the artificial neurons would in fact be unable to interface with the biological neurons in the same way, but then they would not be functionally identical. Remember, the argument is only that IF the artificial neurons could reproduce the behaviour of the biological neurons closely enough THEN they would also reproduce the qualia. Roger Penrose believes that there is something special about the physics of neurons which is fundamentally non-computable, so that it would actually be impossible for a computer to reproduce their behaviour, and therefore impossible for a computer to reproduce qualia. This is a self-consistent position, in contrast to that of John Searle, who holds that it might be possible to reproduce the behaviour of neurons but not the qualia. However, there is no evidence for this postulated non-computable physics.

1. Small scotomata are usually, not sometimes, filled in — see Ramachandran & Blakesley on this. 2. Broca's area constitutes only a small part of the speech area of the brain. 3. To suggest that the activity of certain neurons are the neural correlates of consciousness (or of qualia) necessarily implies that NCCs are not identical to quali— because, if A is a correlate of B, then A cannot be B. Normally, then, NCCs (A) affect the behavior of qualia (B) because of necessary causal relations (call these P) between them. Then, if the neurons are replaced with silicon chips, which can process their inputs in the same functional way as the neurons they replace do, it is purely an empirical matter of fact whether P can, or cannot, also interact with these silicon chips in the same way that P normally interacts with NCCs. Of course one can simply say instead, as eliminative materialists do, that neurons and qualia are identical (running foul, however, of Leibnitz's Law of the the Identity of Indiscernibles in doing so) — in which case neurons are not NCCs—they are qualia. I prefer to reject eliminative materialism. All this highlights the current widespread confusion in neurophilosophy over the concept of 'identity'.

Brent, The neurons in the motor cortex responsible for speaking and hand-waving don't experience vision themselves. They receive input from the upstream neurons in the visual cortex, and then report that the strawberries are red and the leaves green. If artificial neurons in your visual cortex produce the same electrical output (while lacking qualia), then as far as your motor neurons are concerned you have seen the strawberries as per usual. So you will say that the strawberries are red and the leaves are green and move your hands as if the strawberries are red and the leaves are green, EVEN THOUGH you actually see nothing at all. Do you see the problem with this idea?