Australian National University's Centre for Consciousness has a nice collection of essays by U of Arizona philosopher David Chalmers and others. See, for beginners, Chalmers's essay "Facing Up To the Probolem of Consciousness." Chalmers in one of the leaders in this whole discussion, and nicely explains the "easy problems" of consciousness and the "really hard" problem of consciousness.
Re. the latter Chalmers writes: "The really hard problem of consciousness is the problem of experience. When we think and perceive, there is a whir of information-processing, but there is also a subjective aspect. As Nagel (1974) has put it, there is something it is like to be a conscious organism. This subjective aspect is experience. When we see, for example, we experience visual sensations: the felt quality of redness, the experience of dark and light, the quality of depth in a visual field... If any problem qualifies as the problem of consciousness, it is this one. In this central sense of "consciousness", an organism is conscious if there is something it is like to be that organism, and a mental state is conscious if there is something it is like to be in that state. Sometimes terms such as "phenomenal consciousness" and "qualia" are also used here, but I find it more natural to speak of "conscious experience" or simply "experience"."
Chalmers says: "An analysis of the problem shows us that conscious experience is just not the kind of thing that a wholly reductive account could succeed in explaining." He says, at this point, some just give up. it's the kind of thing that makes one think the problem of consciousness is in principle unsolvable. Chalmers is not so pessimistic. He writes: "This is not the place to give up; it is the place where things get interesting. When simple methods of explanation are ruled out, we need to investigate the alternatives. Given that reductive explanation fails, nonreductive explanation is the natural choice." He goes on to outline his principles for a nonreductive explanation of consciousness. Very interesting!
