Hi Jeremy -

What I am suggesting is an account of what I would expect to happen as Joe has his brain progressively 'siliconised'. I am suggesting that, unless unusual technical devices are deployed to keep his beliefs and reports constant, he will notice that his qualia are fading, and his functional profile will track that change. So when he gets to the point where his qualia have all but disappeared, he will notice this and accurately report it. So in that event I accept the principle of organisational invariance; particular experiential states determine particular functional profiles. 

If, on the other hand, unusual technical devices are deployed to keep his beliefs constant, this is only because the usual felicity of his reports has been disrupted. There is no absurdity. If we take Joe's career to the point where he is completely siliconised, I can even accept that he will end up reporting vivid qualia when he has none at all. 

So it really doesn't matter. Either he notices and reports his fading qualia to the end, or he is in some way forced to believe and report falsely that his qualia remain constant. No absurd consequences occur in either case.

That is the main point: I have presented a common-sense account of what would happen, and I think the burden is on Chalmers to say why it could not happen. Specifically, I am asking him to explain why he thinks that any circumstance in which Joe is simultaneously experiencing fading qualia and yet continuing to report them as being normal must be absurd. I don't think he has provided that explanation.

The second point is that whatever we conclude about Joe, as an originally fully conscious person, has no bearing on what mental-functional correlation laws must apply to a robot which has never been conscious. Joe's qualia reports might well track his fading qualia even to the point of extinction, but they do so in virtue of the change. A permanently mindless robot suffers no such constraints. 

I suppose Chalmers could argue that if Joe's functional profile can be made to remain constant without disrupting the felicity of his qualia reports (which he has not shown to be the case), then it follows that silicon can support consciousness. Even then, however, he hasn't shown that silicon must support consciousness. He will only have shown that under the specific conditions which enable Joe to maintain his original functional profile while his brain is replaced with silicon will he experience constant qualia. Again, the permanently mindless robot which is an exact functional simulacrum of the original Joe remains possible.