I have been thinking about writing about my thoughts on this subject for a long time, and finally like things usually do it happened very suddenly. I was about to go to bed when I felt a sudden urge to write about it This Very Instant. I couldn't bear the remote possibility of not waking up tomorrow and my thoughts never be written. A number of fortuitious factors finally came together to urge me to do this. First I started listening to an audiobook: Bertrand Russel's excellent History of Western Philosophy, secondly I was reminded of this website, and thirdly I saw a reddit post where someone asked about pain "Why can't the body just warn us some other way, like some sort of warning pops up that we need to change position otherwise we might break our back or something, instead of some unnecessary torturous pain". I think this is an absolutely excellent question.
Now if this were any other topic I would begin by defining my terms, but this is quite difficult. It is indeed almost the entire problem. But of course giving up won't do. We must have something, even if tentative. So let's try. "Qualia are those sensations that humans feels." This is quite insufficient but it is something. Another approach, examples. When you smell a flower that is qualia. When you look at the sky and see blue that is qualia. This is progress, but there is another key part to it, namely what qualia is not. It is not anything physical. It is not the photoreceptor in your eye catching a photon. It is not an ions travelling down an axon. It is not the release of glutamate in a synapse.
Now a natural question is "does such a thing really exist? non-physical?". The subjective nature of the whole thing makes it hard to logically convince someone of that. I can only encourage introspection.
Why bring up qualia and free will together? Because as far as I see they are sort of inverses. When information passes from the material world to the soul, we call that qualia. When information passes from the soul to the material we call that free will. This is a very important relation. Some people accept qualia without accepting free will, but I have question for them: How can we talk about qualia? When I say I feel qualia, isn't that a statement about what occurs in the soul, hence doesn't it require the body to detect the soul in some manner, to be influenced by it in some manner? This does seem to prove that influence goes both ways.
The big difficulty in studying qualia and free will is how subjective they are. This makes it hard to talk about them and it makes it hard to design experiments on them.
But I think finally that pleasure and pain could be a key to the puzzle. Because pleasure feels good and pain feels bad. This is quite mysterious. Most other sensations are quite hard to describe, but about this ones we can say something. Where people wonder "what if what I see as red you see as green and vise versa" no one can reasonably ask the same about pleasure and pain. This seems like a crack in what appeared to be a solid wall. Isn't it tempting to try to dig in and crack it wide open? My idea is as follows. Try to modify the brain somehow until pleasure no longer feels good. Or one could instead modify the brain until a normally neutral stimulus feels pleasurable. If one could find the minimal difference on a physical level between a pleasurable and a non-pleasurable stimulus then that does seem like it would bring us closer to solving the riddle?
Now if you ask people why do somethings feel good, on a neural level chances are they will bring up neurotransmittors. It feels good because of serotonin. Or dopamine. But on closer inspection it does not seem quite as sufficient as an answer. If you fill a jar with serotonin the jar will not feel happy. Or at least we don't think it will. So serotonin by itself can't be the essence of feeling good. Rather it must be its effects on the brain that feels good. Next perhaps someone might suggest that it's certain areas of the brain that feel good when they are activated. This does sound a little more plausible but still quite incomplete.
However this lets us get closer. Consider checking which parts of the brain are activated by serotonin. Then somehow activate them in a different way. Perhaps electricity or magnetic fields. Does this feel good? It does? Now try to activate fewer of them, and fewer. Hone in on the pleasure.
Okay but why do those regions feel good? Can we make them not feel good? Is the direct consequence or is it like with serotonin just an intermediary?