(This post grew out of an old conversation with Wei Dai.)
Imagine a person sitting in a room, communicating with the outside world through a terminal. Further imagine that the person knows some secret fact (e.g. that the Moon landings were a hoax), but is absolutely committed to never revealing their knowledge of it in any way.
Can you, by observing the input-output behavior of the system, distinguish it from a person who doesn't know the secret, or knows some other secret instead?
Clearly the only reasonable answer is "no, not in general".
Now imagine a person in the same situation, claiming to possess some mental skill that's hard for you to verify (e.g. visualizing four-dimensional objects in their mind's eye). Can you, by observing the input-output behavior, distinguish it from someone who is lying about having the skill, but has a good grasp of four-dimensional math otherwise?
Again, clearly, the only reasonable answer is "not in general".
Now imagine a sealed box that behaves exactly like a human, dutifully saying things like "I'm conscious", "I experience red" and so on. Moreover, you know from trustworthy sources that the box was built by scanning a human brain, and then optimizing the resulting program to use less CPU and memory (preserving the same input-output behavior). Would you be willing to trust that the box is in fact conscious, and has the same internal experiences as the human brain it was created from?
A philosopher believing in computationalism would emphatically say yes. But considering the examples above, I would say I'm not sure! Not at all!
We do, on the other hand, know subjecively what pain feels like..
That's not the point. The point is that if we have words referring to subjective sensations, like "purple" and "bitter", we can distinguish them subjectively. But if we discard out subjective insight into them, as you are proposing, and replace them with vague objective descriptions -- vague, because no one knows precise descriptions of the full gamut of atomic configurations which implement pain. -- then you take a step backwards. You can't distingusih a brain-scan of someone seeing purple from a brainscan of someone tasting bitter. Basing semantics on objective facts, or "reality" as you call it. only works if you know which fact is which. You are promoting something which sounds good, but doesn't work -- as a research program. Of course it works just fine at getting applause from an audience of dualism-haters.
Are you talking about realisations or representations?
No one has made that argument. The point is not that it is not ultimately true that subjetive states are brain states, it is that rejecting the subjective entirely, at this stage, is not useful. Quite the reverse. Consciousness is the only thing we know from the inside--why throw that away?
If we know what casues or predicts something, then we can sometimes reproduce it in radically different ways. That is the basis of artificial intelligence: realising intelligence in a medium other than a brain.
But you are saying that pain cannot be realised by a robot, and your reasons for sayign that are entirely non-empirical.
We might be able to refine the concept of consciousness as part of a research programme, but research programmes have to start with folk concepts.
I know that the experience of stubbing my toe is called pain, and I know that what I'm sitting on is called a chair. But I don't know the "precise descriptions of the full gamut of atomic configurations which implement" them in either case. This is very normal.
You seem to be under impression that I advocate certain methods of examining brains over others. I don't know where ... (read more)