You know, I think we're getting lost in the little details here, and we keep communicating past one another.

First, let me emphasize that I do think we'll eventually be able to explain consciousness in a reductionist way. I've tried to make that clear, but some of your arguments make me wonder if I've failed to convey that.

Second, remember that this whole discussion arose because you questioned the value of trying to answer the hard problem of consciousness. I now suspect what you originally meant was that you don't think there is a hard problem, so there wasn't anything to answer. And in an ultimate sense, I think you're right: I think people like Thomas Nagel are trying to argue that we need a complete paradigm shift in order to explain how qualia exist, and I think they're wrong. Eventually it almost certainly comes down to brain behavior. Even if it's not clear what that pathway could be, that's a description of human creativity and not of the intrinsic mysteriousness of the phenomenon.

But what you said was this:

Is the answer even relevant ?

As far as I understand, there currently exists no "qualia-detector", and building one may be impossible in principle. Thus, in the absence of any ability to detect qualia, and given the way you'd set up your thought experiment about the sleepwalker, there's absolutely no way to tell a perfect sleepwalker from an awake person. As far as everyone -- including the potential sleepwalker -- is concerned, the two cases are completely functionally equivalent. Thus, it doesn't matter who has qualia and who doesn't, since these qualia do not affect anything that we can detect. They are kind of like souls or Saganesque teapots that way.

This, to me, really sounds like you're saying we can't detect qualia, so we might as well assume there are no qualia, so we shouldn't worry about how qualia arise. Maybe that wasn't your point. But if it was, I stand in firm disagreement because I think that qualia are the only things we can care about!

For some reason I can't seem to convey why I think that. I feel rather like I'm pointing at the sun and saying "Look! Light!" and you're responding with "We don't have a way of detecting the light, so we might as well assume it isn't there." (Please excuse the flaw in the analogy in that we can detect light. Pretend for the moment that we can't.) All I can do is blink stupidly and point again at the sun. If I can't get you to acknowledge that you, too, can see, then no amount of argumentation is going to get the point across.

So all I'm left with is an insistence that if my understanding of the universe is completely off and it turns out to be possible to remove conscious experience from people, I most certainly would not want that done to me - not that I could care afterwards, but I absolutely would care beforehand! So to me, the presence or absence of qualia matters a lot.

But if you cannot relate to that at all, I don't think I'll ever be able to convey why I feel that way. I'm completely at a loss as to how this could possibly be a topic of disagreement.