Materialism has made a great deal of progress in explaining the mind in terms of a completely physical process happening in the brain. The first person perspective, intending, representing, these were once all considered things that were unexplainable by materialism, but over time philosophers have shown how these aspects of the mind can be explained be purely physical events (although obviously complete descriptions have to be left to neuroscientists). However, there still remains one major explanatory hurdle for materialism: qualia. I am not one of the philosophers who think that qualia prove that the mind can’t be explained in materialist terms, there are many good reasons to believe that the mind must have such an explanation. But I wouldn’t deny that qualia, and the explanatory gap, are a problem that materialism needs to address.
I don’t think qualia are an in surmountable problem, as some do, because it seems like an open question whether a particular qualia are really some brain process (by open question I mean that it seems rational to ask how or why it is that brain process). All open questions show is that we are ignorant about some of the necessary details, making the truth of the identity seem obscure. For example, our ancestors may have thought that the identification of water with H2O was an open question (is water “really” H2O?), especially since water seems to have properties, such as infinite divisibility, that H2O does not. But eventually such skepticism about identity claims tends to disappear, especially when it can be shown that H2O really can play the role of “water” (it has all the same objective properties, although obviously not the same subjective properties, since at the very least they have different names).
Thus the fact that identifying qualia with some brain process feels like an open question really reveals that we simply haven’t shown that some brain process can play the same role as qualia, not that they are necessarily distinct.* And trying to remedy this problem illuminates some of the real problems that make qualia so hard to address under materialism. Simply attempting to define what a qualia is can be a serious problem. We can roughly describe a qualia as experience as given to us. For example “redness” is a kind of qualia. But this doesn’t actually pin down what qualia are, at least not enough to be able to say if something definitely is a qualia or not, it is simply suggestive. Imagine attempting to define “redness” to someone who has never seen red (without simply avoiding the question by saying “a kind of qualia” or “a kind of sensation”). The only way to convey what “redness” is seems to be by pointing out things that evoke the sensation of “redness” (the color or roses, ect). Or if we are more poetical we might attempt to describe how “redness” makes us feel in terms of associated sensations (it feels “angry” or “dangerous”).
But, if that is the role that the physical process must play, then there seems to be no problem in capturing it in materialist terms. What a specific qualia, like redness, could be, physically, is a combination of two things. One is a specific kind of visual input. We can conceive of the visual input, which is integrated into experience as visual sensation, as an array of numbers (as what is happening physically, not as how it is presented to us; it is presented to us as just a certain color, different from other colors). Redness then would be a distinct number. Additionally this number is combined with associations**, both of other objects that have evoked this particular visual input, and possibly with memories, feelings, ect that the mind has linked to this input for some reason. Many of these associations are unconscious (or at least at the periphery of awareness), but we can assume that when focusing on the specific sensation they are more likely to be brought to our attention. We can assume that thinking about red, instead of experiencing it, is simply a process of imagining red, in which the usual visual input in now being generated by imagination instead of perception. This physical process can play the same role of “redness” as described above. Redness, being some particular kind of visual input, is naturally the kind of thing you can’t explain in words directly, since it is part of your neural activity, and not something that can described directly. Instead we must appeal to the associations, which are generally publicly accessible objects, and by using labels such as “red”, which are really just shorthand for these associations.
Given this definition can we address the problem of Mary the color scientist? (See here for my description of the problem.) I think we can, because part of what defines individual the qualia are a specific kind of sensory input. Even if Mary learns what specific neurons and firing patterns are involved in this qualia she doesn’t possess the concept of red as we do, because when we think of red we generate red in our imaginations (simulating the experience of seeing red). But even learning what “redness” is doesn’t enable Mary to make the right patterns of neurons fire (the neurons that are the “red” visual input); that is just not an ability we have, to go from a description of the way the mind works to making our minds work in that way. So Mary “learns” something new about red when she first sees red, because now she is able to think about it in the same way we are, by imagining it. But she hasn’t learned anything new about the qualia of redness, she has simply acquired a new way of thinking about it.
So does the account given here really explain qualia? I am willing to entertain the possibility that there is something more that qualia do for us, some additional role they play in the mind that is not captured by the description that I have given here. The problem is identifying what that role is, so that we can determine what physical descriptions could play that same role (or if they could play the same role). And to be honest with you I simply can’t see what qualia are supposed to be beyond the description that I have given here. This is not to say that I am unaware of other descriptions of qualia, just that they are so vague that they don’t really inform us as to what properties something must have to be a qualia, and thus of little help in determining whether some physical process really is a qualia.
* Defining what role a specific concept plays is often essential to determining what it is exactly. For example, meaning, knowledge, ect.
** I have discussed in other places how our experience is saturated with concepts, when we see a tree we don’t see simply a visual impression, we see a visual impression as a tree, and this “seeing as” is part of the experience, not something we add to it by reflecting or thinking about it. These associations then should be simply treated as another example of this conceptual saturation.