The Problems of Consciousness
Consciousness, or subjectivity, or the inwardness of human experience, or whatever we are going to call it, is a unique problem. In fact, many of the features that make it unique are the very features that make it a problem in the first place.
Just what do we mean by "consciousness"? Although there are many words that get close to the concept, and many indirect and more or less complex ways of talking about it, one of the oddities of consciousness is that there doesn't seem to be a single unambiguous word for it. (Follow this link for some discussion of the "how to talk about it" question, and some things that we do not mean by "consciousness" in this essay.)
In essense, though, what we are talking about is that aspect of experience which is inner, which is subjective, which is available to me in a way that it is not available to anyone else. Although we don't have a very good single word for it, everyone seems to catch on pretty quick to what we're talking about (we have a thought-experiment about someone who doesn't).
Once we seriously consider the odd nature of this ineffable subjective innerness that we're calling "consciousness", a number of hard questions appear. We'll list them and treat them mostly separately, although of course there will be considerable overlap. (Readers may follow the links in order, or browse at random; we've tried to arrange the material to suit either style. For those who like the Big Picture, there is also a site map for all the Problems of Consciousness pages, as well as a change history.)
In thinking about these primary problems of consciousness, we will also brush up against a number of other hard problems, and while they do not stand as directly in our path as the ones above, they are not entirely orthogonal to it, either. (The points below will gradually become links, as the pages come to exist!)
Note that we have solutions to very few of these problems! We do, however, intend to lay out as clearly as we can the nature of each problem, and the range of plausible solutions and solution-seeds of which we are aware. We also intend to gather a useful, and usefully-annotated bibliography, citing previous work done by others, on whose shoulders we stand peering into the darkness.
We eagerly solicit help in this endeavor; suggestions, corrections, ideas, and references may be sent via email to firstname.lastname@example.org.