Mr. Harnad:  "It seems to me I can know perfectly well (and cartesianly, hence incorrigibly) that I have a toothache, regardless of whether I have a tooth, or even a mouth, let alone whether anyone else is measuring or can measure anything, on my body or anywhere else, and whether that measurement does or does not correlate with the existence or locus of my tooth (or mouth) or pain."

I don't know about the "Cartesionally." I grant that you can know that you have a toothache, but not if you don't have a tooth, unless you want to define "toothache" to mean something other than an aching tooth.  If so, then what is a toothache?

More broadly, what are feelings?

How do you know they exist?

How do you know they don't cause anything?

And how do you know they correlate with brain functions?  (I still see a contradiction in the view that they could be only subjectively knowable, and yet known to correlate with objective processes.)

Without answers to these four questions, I'm afraid I will not see the sense of epiphenomenalism.

Mr. Harnad:  "It's exactly the same problem (and I really mean exactly) when you are asking about how/why seeing blue feels like something or you are asking about why/how going into a blue funk feels like something."

Yes, as I noted, we are in the same philosophical boat whether we are talking about inner or outer perceptions.  But the point I was making when you offered this response was about our current scientific understanding of the relevant processes.  Philosophically, yes, it is the same situation, but I would not call it a "problem."

So, again, to the broad question, why are some functions felt?, I would answer, what are you talking about? 

For one thing, I would not say that these functions are felt.  That would imply that there is something else apart from the functions which is feeling them.  That would be to relocate to locus of feeling, and I see no possible destination.

I see nothing problematic about regarding feelings as neurological functions interacting with other neurological functions, just as I see nothing problematic about regarding colors as wavelengths of light interacting with neurological functions.  The idea that these functions could occur without the feeling of color vision implies a notion of feeling which I do not understand.
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