SH: ""How" is about the causes of feeling and "Why" is about the effects of feeling."

I'm unclear on what you mean when you say: ""Why" is about the effects of feeling." Are you talking about the same cause-effect pair in the above descriptions of "How" and "Why"? That is, do "the causes of feeling" (given in your description of "How") cause "the effects of feeling" (given in your description of "Why")? Because the effects of "the causes of feeling" would just be feeling itself, or the existence of feeling.

SH: "I don't know about David, but I don't lose much sleep about whether the brain causes feeling (of course it does); and if the only problem with explaining how the brain causes feeling had been some uncertainty about objective measurement of feeling, I would not give such a small explanatory gap much thought. "

Would it be fair to say, then, that the explanatory gap is not concerned with the question of how? Also, wouldn't the answers to the "how" question (or "the complete microphysical truth about the universe") exhaust all of the functional, causal explanations? If so, what form of explanation could answer the "why" question?

SH: "No, for me the real puzzle is the "why" aspect rather than the "how" aspect. For whereas it is merely mysterious how the brain causes feeling (but there is no doubt that it does), the real explanatory puzzle is why the brain causes feeling, since there is no room for feeling to have any causal power of its own (even though it feels as if it does)"

I don't believe that the explanatory gap is also a question of free will. The putative feeling of free will is just one feeling/sensation/perception/thought among many. The explanatory gap as I understand it is to provide an explanation for the mere existence of any and all feeling, in addition to the functional explanation for how the brain causes that feeling.

LC