One trap that we must be wary of is adopting beliefs because they are popular among people who strive to think critically or scientifically, as opposed to being the result of critical or scientific thinking. One good example of this is RationalWiki which purports to report the political beliefs which all Rational(TM) people should hold. Similarly, I believe that most people who believe in materialism do so on the basis of extremely poor reasons and without knowledge of some of the stronger arguments for qualia existing. Maybe we should ultimately support materialism, but I get the impression that many people jump to this conclusion too quickly. Here are some points I believe people should consider first
(I know someone else in the rationality community wrote a post arguing for consciousness recently and I was meaning to read it, but I lost the link before I had a chance)
Failure to bite the bullet argument
If qualia don't exist, why is anything that you experience good or bad? In this case, things like pleasure, pain and meaning are nothing more than ways that particles can combine. But if this is the case, why are these combinations special or more important than other combinations? Why should we try to make certain combinations happen and certain combinations not?
It's fairly common to deny the existence of the objectively good or bad, but denying the existence of the subjectively good or bad is a much stronger claim. But everyone acts like this matters and so it appears somewhat hypocritical. And there is an argument that we should continue to act normally on the basis of meta-theoretic uncertainty, but no-one makes that argument.
Pascal's Wager Argument
This last point is actually a pretty strong argument for believing in qualia. If they don't exist, nothing matters, but if they do exist then we benefit from acting as though they do exist. Therefore, we should assume the later.
Expected Evidence Argument
Claiming the existence of qualia is often seen as anti-scientific, some people would even go as far to say that they don't see much difference between claiming the existence of ghosts or qualia. One key difference is that if ghosts existed we would expect objective evidence of them, even if the experiments would be hard to run. For example, we would expect a greater rate of howling in houses where someone was murdered. Even if they could only interact with us psychically, we would expect a higher rate of mental illness in these houses, even if the person living there had no idea of the past. Since if ghosts existed we would expect the existence of objective evidence, the lack of any such evidence counts against them.
On the other hand, it's not so clear that we should expect any objective evidence of subjective experience. Arguably, the only evidence we should expect of subjective experience is direct, subjective evidence. So the absence of objective evidence provides no Bayesian evidence against the existence of qualia.
Initial Foundations Argument
How should we come to understand the world? It seems like we might want to first pick a class of phenomena to be the foundation and that this should be whatever we are most certain of existing. We will then need to decide on the best way of knowing about that phenomenon and then choose a way of figuring out what other kinds of things might exist in the universe.
So what should our initial foundations be? One option is the external physical world, while the other is subjective experience. The later makes more sense to me as it describes why we believe in an external world. It isn't that we just assume it a priori, but instead that we notice patterns in our subjective experience and then theorise that there might be some object that exists independently of our experience causing these regularities. On the other hand, subjective experience makes much more sense to assume a priori and hence more sense as an initial foundation. Indeed, we could even say that this approach is truer to the scientific method since we even subject our belief in the existence of the external world to an empirical test. In other words, objective experience needs to be justified in terms of subjective experience and not the other way round.
Transcendence Argument
Arguably the nature of an atom (or whatever elementary particle we choose) transcends its mere mathematical description. Firstly, the claim that "THIS IS ALL THAT THERE IS TO IT" seems like a strong claim and one which we can never know for certain. Surely, it is much more reasonable to maintain that there is at least the possibility of there being something in its nature beyond this. Indeed, if there were not, this would seem to imply that a perfect simulation of an atom is an atom and this seems absurd.
Following this reason, why can't there be an element of consciousness that transcends its mere mathematical description? And if a simulation of an atom is not automatically an atom, then perhaps a simulation of consciousness isn't automatically conscious?
Relabeling Argument
Let's suppose I have a system with a variable x which takes values between 0 and 10. Suppose we define a second variable y which is also between 0 and 10 which satisfies x+y=10.
Is this a different system than the original? It seems this comes down to whether y is a new entity or just a relabelling of x. The one thing that I would expect to be uncontroversial here is that it is possible for this new system to just be a relabelling. Whether or not it is necessarily just a relabelling would be much more contentious.
If we were to say that sometimes introducing a variable that like that could be more than just a relabelling, then that would be to accept that objects can have a nature that is not fully encapsulated by their mathematical definition as I previously argued.
On the other hand, if circumstances like this are always just a relabelling, then there is no difference between the system with y in it and the system without y in it. This becomes important when y is a much more complicated property, such as the amount of "pain" an organism is experiencing. If the system is the same with the entity representing pain or without this entity, then it seems like it can't have been important. This implies that someone insisting it was just a relabelling must then bite the bullet of qualia being unimportant.
Relational Argument
I'll quote Consciousness Comes First:
The issue is that physical properties are by their nature relational, dispositional properties. That is, they describe the way that something is related to other things and/or has the disposition to affect or be affected by those other things.
... However, if all we ever have is relational/dispositional properties—that is, if everything is only defined in terms of other things—then, ultimately, we have defined nothing at all.
It’s as though someone created a very elaborate spreadsheet and carefully defined how the values in every cell would be related to the values in all of the other cells. However, if no one enters a definite value for at least one of these cells, then none of the cells will have values.
In the same way, if the universe is to actually exist, its properties can’t be exclusively relational/dispositional. Something in the universe has to have some kind of quality in and of itself to give all the other relational/dispositional properties any meaning. Something has to get the ball rolling.
This argument is very similar to the transcendence argument and the relabelling argument in that it asserts things can be more than their mathematical descriptions, but still different enough that I felt it was worthwhile including separately. Interestingly the article argues the consciousness and conscious observations are what actually get the ball rolling, although I haven't thought this through enough to have a strong position yet.
Against the Illusion Argument
Some people say consciousness or qualia are just illusions. At best, this seems like a really bad analogy. For example, if I think I see an oasis, but it is actually an illusion, then it is the oasis that is illusionary and not my experience of seeing. In other words, if an experience is an illusion, then we still have the experience of seeing that illusion. And any discussion of illusions where the illusion isn't experienced seems to be a very misleading way of using that term.
Arguments against consciousness
I'll finish by noting that there are some very strong arguments against consciousness too. For quite a while I felt that the epiphenomenal theory was the most plausible, but there are two devastating critiques. The first is the evolutionary argument, it seems absurd that positive qualia would line up with events that are evolutionary advantageous and negative qualia would line up with events that are evolutionary disadvantageous if qualia has no causal mechanism to impact evolution. And the second is that it sure looks like qualia has a causal impact, since we are discussing them right now. So to believe in the epiphenomenal theory is to believe qualia for a reason completely independent from us actually having qualia.
These are very strong arguments, but I nonetheless worry about closing the door on this debate too quickly as there are quite possibly theories that we haven't considered yet, especially when there appear to be very strong arguments for qualia as well.
The question is relevant only to the extenet that physical world event and perceptions are intermingled. I used simplist language, I infact know a lot of interesting things about color perception which you could not have deduced from my simplistic language.
For example for the question "can something look to have a certain color but actually have a different color" there is the illusion about a cylinder casting a shadow on a chessboard. Then there is what on what in chess terms would be different colored squares one outof shadow and one in shadowm marked A and B. The image is made so that if you compare the fill color of A and B on a monitor they have the exact same color values. But when humans are presented with the picture and claimed that A and B are the same color they can't believe it. The human brain is such that when it recognises that something is in shadow it presupposes that the material would in more ordinary lighting be a more bright color and part of what makes the illusion work is that when people refer to "color" they have a closer association to the lightning-invariant color than to the kind of absolute color that computer monitor pixels have to assume. Quesitons of the form "what is the wavelength of light that makes you see orange" have presuppositions that get overruled by this lighting context. Under orange lighting the criteria on what wavelengths are counted as orange get tighter.
Going over what I wrote I notice a possible ambquity. "materialist theory" can refer to any theory whose primary ontology is fairly described as "materia" or it can be read as the top honed result of what "materialist starting point theory" has provided. A toy model belonging to the wide category doesn't do justice for exemplifying explanatory power. But the point was to clarify that there is the evidence, the suppositions that are used to make sense of the evidence and the abstract hypotheses that are either bought or disbelief based on understanding. In the visual processing system taking into account shadows it assumes the existence of shadows as appropriate transformations on raw data to get useful data. The brain assumes out of habit or without justification that shadows happen and on the abstract layer it becomes diffult to doubt them. A and B seem like different colors and as the abstract reasoner you have little clue that the assumption of shadows was used to derive those colors. "they just appear to be different color" as a matter of fact. But if you had to do the job that your visual cortex does automatically by hand you could see how the raw data doesn't necceciate that result. Looking pixel by pixel you can see that the color values match.
There is also color perception that does not enforce a materialist-handy set of assumptions. There is a form of synesthesia where letters are seen as colored. It's not that super mysterious as letter-contex is not that different from shadow-context. But somebody having these kinds of experiences is much less likely to think of these as objective qualities world objects have. You don't get confused as black object turns to red as you recognise it to be a t-letter. But sometimes your emotional state can color your perception of others feelings. If you are feeling paranoid you can think of everyone else as paranoid even without realising. This kind of experience can feel a lot like "just directly accessing that persons objective paranoidness" I guess you could have a sort of synesthesia where you color people based on what you think their mood is. If you did have emotional processing this automatic it could be hard to entertain that your emotional logic could be wrong "offcourse he is sad, just look how blue he is!"
I appear to have rambled but the point is that "simple color perception" is just open to be abstractly wrong as coloring sad people as blue. It's hard to rule out that you are literally seeing red because you are synesthesing your anger into your experience. But the standard interpretion "I am seeing red because the environment is uncaringly having electromagnetic state in my location" suffers from same sorts of difficulties.