There are basically three ways in which we can support the claim that the know something. One, the most common, is that the things we know are the best and simplest explanation of observations. This is why we believe that an independently existing external world exists, it the best and simplest explanation for the consistency of the world, the fact that the world can surprise us, and the fact that the world doesn’t directly respond to our will. A second way in which we might know things is if is impossible for things to be otherwise, given our understanding of truth. It is this reason that motivates us to conclude that we exist, because in order to doubt that we exist something must exist, at the very least the doubt itself. And finally there is “revealed knowledge”, facts that are simply apparent to people and can’t be denied, as they see it. Revealed knowledge is the basis for qualia/phenomenal properties, as well as the belief in god. The first two are uncontroversial ways to support a claim of knowledge, but the third is not.
It is my claim that revealed knowledge is knowledge only in name, because the facts we “know” in this way are no more or less likely to be true because they were revealed. I would say that all we need to do is explain why such facts are felt to revealed and undeniable, and we have explained all there is that needs explaining. Now the explanation may be that the facts are as they seem, but it might also be just a reflection of the structure of our psychological constitution, and thus the supposed facts revealed to us by it might indeed be false.
Of course as I have described it reveled knowledge seems obviously ridiculous. We are subject to all sorts of cognitive illusions, for example the fact that in certain drawings one line may seem to be longer than another even though they are actually the same length. And it may be that even when we know that it is an illusion we may still feel that one line is longer. Although we may admit to being fooled this admission is a second-order judgment. Our first-order judgment keeps telling us that one line is longer, and nothing we can do or think will change this judgment, but because of our capacity for reason our second-order judgment overrides this, and so we don’t allow that first-order judgment to influence our thinking about the matter. Thus this is a case of revealed knowledge being inaccurate (and accepted as inaccurate), although we know better one line is still presented to us as longer; we cannot deny that judgment, only overrule it.
But the defenders of qualia do not believe that qualia are such revealed knowledge. They agree that revealed knowledge is bad, and that it can’t be relied upon without independent confirmation, and that it might indeed be false. But, they say, qualia are not something that can be simply explained away, like god or optical illusions. Unlike god, they claim, they are not invented to explain some observations, they are an object of study that needs explaining. This, in my opinion, is at best a verbal trick, because it does not address the problem that revealed knowledge is often bad. Instead it addresses how certain kinds of “best explanations”, the first type of knowledge mentioned, may turn out to be false, when we have some kind of psychological bias that motivates us to pick a less than optimum explanation all the while thinking of it as the best explanation. It is true that some people do think they have knowledge of god, and UFOs, in the “best explanation” kind of way, and it is true that we often explain why their conclusions are wrong by appealing to a psychological bias that interferes with their ability to find the best explanation. But this is not the kind of knowledge that we were comparing qualia to. We were comparing qualia to the kind of knowledge of god people have when they claim that they can simply feel god’s presence (or some other feature of god, like his love), without backing that assertion up with a reason, they simply feel it. Just like almost everyone simply sees one line as longer than the other in the illusion. And just as we simply feel that consciousness has certain phenomenal, qualitative, properties. If we say that qualia must be explained, without being explained away, because of this kind of immediacy then we can make the same claim for god and optical illusions. If we can’t explain qualia by explaining how our psychological constitution would lead us to think that qualia exist then we can’t explain our judgment that one line in the illusion is longer than the other by appealing to the psychological facts either. Instead we would argue that the line must be longer because it appears in an immediate way to be so, and that the only satisfactory explanation of this fact is one that does not deny that the line is indeed longer. Clearly this is ridiculous. It is perfectly acceptable to explain the illusion by explaining why we see one line as longer by appealing to psychological facts about the way we process images. And thus it should be perfectly acceptable to explain qualia by explaining why we think that experiences have a characteristic feel by appealing to psychological facts about the way we have access to our own experience.
Thus if we are to believe the claim that qualia or god exist they must be justified by one of the other two possibilities. Since there is no contradiction in denying that they don’t exist only the first option is a real possibility. But if we are to justify them as the best explanation of certain observed facts then they must play some causal role in events, either by directly being causes, or by being descriptions of certain kinds of situations that can act as causes. Which in turn means that one must accept either the thesis that the physical world is not casually closed, or that qualia, or god, are really something physical, and hence not as special as we first supposed.