Philosophers in the analytic tradition are very good at defining problems, but not so good at actually answering them. This is particularly obvious in attempts to address the problem of consciousness. Here the problem is well defined, but, although there has been a lot said, most of it is highly speculative and flawed.
At the heart of the problem of consciousness is a mystery: there is a subjective, felt quality to experience that isn't explained by science. Science can explain how stubbing my toe causes nerves to fire, carrying a signal to my brain that I have damaged my toe, but there isn't a good explanation for the subjective experience of pain this causes. We understand how the ear works and how aural signals travel to the brain, we have an understanding of how these signals are processed by the brain, but we don't have an understanding of the feeling that is part of listening to a beautiful piece of music.
The felt quality that is mental experience has been described by David Chalmers as the Hard Problem of consciousness. This is in contrast to the easier problems of consciousness; such as the difference between being awake and asleep, the ability to have thoughts about thoughts, our self-conscious awareness. The Hard Problem is the subjective, what it is like, aspect to experience; sometimes called phenomenal consciousness. To Chalmers, the easy problems are amenable to the methods of science, the Hard Problem is not.
Modern arguments about consciousness tend to be between two points of view. Physicalists hold that everything is physical; there is nothing beyond the physical world. Science should be able to explain everything in the physical world, our minds are physical and so science will eventually explain consciousness. This means that descriptions of mental processes, such as subjective experience, will be explainable in terms of physical processes. In the opposing camp are the dualists, these hold that while there are physical processes, there are mental processes that aren't physical; consciousness is not a physical process and so not explainable by science.
Physicalists think that as science has done a pretty good job of explaining the world so far there's no reason why it can't ultimately explain consciousness. Dualists are driven by an intuition that it doesn't seem possible to reduce the rich variety of human experience down to the basic properties of the brain. There appears to be an explanatory gap between phenomenological experience and brain processes.
There are a number of arguments used by dualists to support this perceived explanatory gap; two that crop up regularly are the conceivability argument and the knowledge argument.
The best known form of the knowledge argument comes via thought experiment from Frank Jackson. Mary lives in black and white world; she's confined to a black and white room and learns everything through a black and white television. She is a brilliant colour scientist who knows everything there is to know about colour vision. When Mary is released from her black and white prison and is given a ripe red tomato, it seems obvious that she will learn something new: what it is like to experience red. As Mary knew all the physical facts about colour, if Mary learns a new fact when she first experiences colour then not all facts are physical.
A massive amount has been written on these and I'm not going to go into detail here. The conceivability argument claims that it's possible to conceive of a being that is identical to us, but isn't conscious and so consciousness is not physical. The knowledge argument claims that someone who knew every physical fact would be ignorant of the subjective, felt aspect to experience, and so there are facts that are not physical. The arguments look to exploit a perceived gap between the physical world and the conscious world.
The main argument for physicalism is one of analogy; there have been times in the past when science has been unable to explain phenomena and eventually, through a gradual process of investigation and discovery, a theory has emerged that provides an explanation. There seems no reason why this won't happen with the problem of consciousness.
Both physicalism and dualism rely on intuitions. Physicalism on the intuition that science will eventually be able to explain everything. Dualism on the intuition that there is more to consciousness than the brain and physical processes; there's a feeling that reducing consciousness to the brain somehow demeans it.
Students coming to these arguments for the first time are left both amused and perplexed. Studying the arguments for dualism is certainly entertaining, but unless you take a side they are confusing; they only make sense once you take a side. The arguments themselves don't help decide what side to take, this depends on which intuitions you give more weight.
The argument from analogy for physicalism is easy for a dualist to deny by simply refuting the analogy; I can argue that consciousness is not like the problems science has previously solved and so there is no analogy to be had.
A lot has been written on the arguments for dualism (probably too much), but a physicalist can simply deny the intuition: it is not possible to conceive of a being that is identical to us, but isn't conscious; it is not possible for someone to know all the physical facts and not know what it is like to experience something; there only seems to be an explanatory gap. These arguments fail because they beg the question – they presuppose the answer they are attempting to prove. If I assume dualism the gap is real, if I assume physicalism there is no gap. This is the reason why philosophers discussions on consciousness often go no where. The arguments only make sense if you assume dualism or physicalism, but then you presuppose the answer.
A lot of time has been spent coming up with highly speculative theories of consciousness. What has had far less time spent on is why we have these intuitions in the first place. Basing a whole theory off an intuition is not putting it on firm ground – deny the intuition and you deny the theory.
It is not clear that the sort of introspection our intuitions rely on are even useful to the investigation of the conscious mind. We are all intimately aware of our own consciousness – it is an essential part of ourselves. Everything we perceive is through our conscious frame, and this includes our consciousness itself. I maybe mixing different understandings of consciousness here, but it's certainly true that thoughts about thoughts can have a subjective aspect to them and it's possible that this effects how I understand the original thought.
In the end, the dualist position is untenable and the physicalist one is wait and see. Neither of which are particularly interesting.
So, where does this leave the philosophy of consciousness?
Analytic philosophy has always aspired to a certain level of rigour, it grounds arguments in logic, which in theory can be used to determine whether an argument is true or false. In practice this means that an argument is only good as the assumptions it's built on. Arguments built solely on intuitions are poor arguments. So one fruitful area of investigation might be where our intuitions come from and whether they are a good guide to reality. Some of this can only be answered through empirical study, which is the realm of science, but by framing the question – as Chalmers has done with the Hard Problem – scientists can focus their research and have an idea what a good theory will have to answer. By defining problems, philosophers allow people in different disciplines to understand what the problems really are and what a good answer will look like.
I suspect that part of the reason for the intuition of dualism is the fear that if scientists were to come up with a comprehensive theory of mind it would strip consciousness of some of its wonder. This is silly. Science can explain how mountains and rocks form, knowledge of this doesn't remove the majesty of mountain views – far from it – knowledge of plate tectonics and rock formation provide an additional way to appreciate such things. Knowledge of painting techniques and art history increase the number of ways an artwork can be appreciated. Knowledge and understanding add to experience. A complete scientific theory of mind would enhance the wonder of the mind, not detract from it. There will still be the human condition of joys and pains.
Perhaps, analytic philosophers should become more Continental and spend more time discussing the human condition and what it means to be conscious; there might end up being more truth in what they say, even if they have to give up some of their rigour in doing so.
I finish this essay on a personal note. When studying philosophy of mind at an undergraduate level I was excited by the arguments, I felt there was truth to be had somewhere in them, even if the arguments were often strange in comparison to other areas of philosophy I was studying. Having recently returned to study the philosophy of consciousness at a postgraduate level, I have been left feeling the vapidity of the arguments; notable how so many of the arguments presuppose their answer. This has left me disappointed with this whole area of philosophy. I'm left feeling that to make progress, philosophers in the analytic tradition, either need to become more like scientists with a thorough understanding of neuroscience and psychology, or more like Continental and Eastern philosophers and focus more on the human condition.