@Fil Albuquerque,
... and your thoughts on this:
It is still easy to fall into confusion or to equivocate when talking of "consciousness", so here I will divide the first-person problem into three parts: the problems of sensory qualia, subjective mental content, and the existence of subjective experience.
(1) The problem of sensory qualia
Qualia are the qualitative aspects of our mental states, most obviously of our sensations. The paradigm qualia are those of color sensations; other favorites are the taste of chocolate, the sound of middle C, pleasure and pain. All of these are poorly understood. When we look at a red patch, this sets off a particular pattern of neural firings in our brain. Why should this physical process be accompanied by a rich, subjective sensation? Given that it is accompanied by a sensation, why is it this sort of sensation (the red sort) rather than that sort (the green sort)? There are two issues here: why qualia exist at all, and why particular qualia accompany particular processes. Is the correspondence of qualia to processes arbitrary, or is there some systematicity that we do not understand?
Jackson (1982) has provided the most recent reminder of the qualia mystery, with a sharpening of the argument of Nagel (1974) before him. A future scientist, living in a time when neuroscience is completely understood, might learn everything there is to know about physical brain-processes. But if she has lived all her life in a black-and-white room, she will still not know what it is like to see red; when she sees red for the first time, she will learn something. It seems that the third-person approach, at least as currently understood, cannot tell us about the nature of qualia.
(2) The problem of subjective mental content.
When I think about a lion, something takes place in my subjective experience that has something to do with lions. Again, a straight physical account gives no reason to believe that such an experience should take place. What should a pattern of neural firings have to do with lions? But somehow, my thoughts are about something; they have subjective mental content. It is easy to make attributions of mental content to a system, justified perhaps by causal relations with the external world, but for subjective mental content we need something stronger. We need brain-states to carry intrinsic content, independent of our systems of external attribution; there must be a natural (in the strongest sense, i.e., defined by nature) mapping from physical state to content.
The problem of subjective mental content is not entirely different in kind from that of sensory qualia - the experience of content is itself qualitative, in a way. The main difference is that sensory qualia usually arise during external perception, whereas this sort of mental content arises during thought. (There is also a third-person problem of mental content, which has been raging for years, centering on the question of how we can assign propositional attitudes, such as beliefs and desires concerning the world, to systems and persons. In some ways this is an easier problem, as it may rely on human-defined systems of attributions; these contents may have the status of theoretical entities, rather than states that are presented to us directly. In other ways, the first-person problem is easier, as it may not have to deal with the problem of reference. When I think of a lion, my phenomenology bears some relation to a lion, but the relationship seems more like shared pattern than reference.)
(3) The existence of subjective experience
The two items above are concerned with the nature of our subjective states - why they are one way rather than another. But it is just as deep a problem why subjective states should exist in the first place. Why should it be like anything to be me? If I did not know that subjective states existed, it would seem unreasonable to postulate them. This is perhaps the deepest question of all, and no current theory has come close to dealing with it.
Not many people believe in zombies - humans with normal behavior but without any subjective mental states. These may be logically possible, but it seems implausible that there could be such things in the actual world. At least some people believe there could be functional zombies, however: beings which duplicate the functional organization of humans, perhaps computationally, without being conscious at all (e.g. Searle 1980, Block 1980). The question "what sort of entities can be subjects of experience?" is of great popular interest. For example, is every entity exhibiting intelligent behavior conscious? Could an appropriately programmed computer be conscious? I will argue, by combining first-person and third-person considerations, that the possible existence of functional zombies is implausible.
There are some other commonly-raised first-person problems not explicitly listed above. The problem of self-consciousness (or self-awareness) I take to be a subset of the problem of awareness, of which the difficult aspects are covered by (1) and (2). The problem of personal identity is a separate issue and a very deep one; but Parfit's exhaustive analysis (1986), which combines the first-person and third-person approaches to great effect, gives reason to believe that our first-person intuitions here may be mistaken. It is the three problems listed above that seem to be the residual content of the traditional mind-body problem. I will be using the term "consciousness" broadly to cover the phenomena of all of these problems. If you prefer, replace every occurrence of "consciousness" with "the subjective experience of qualia and mental content."
One difficulty with talking about first-person problems is that for every first-person (conscious) mental state, there is a corresponding third-person (functionally definable) mental state. (Perhaps there are not two different mental states, but simply two different ways of viewing one state; this is unclear. In any event, it is uncontroversial that for every subjective mental event there is a corresponding physical event; the physical event may be viewed via functional abstraction as a third-person mental event). For every subjective sensation there corresponds an objectively characterizable perception. This dichotomy in (ways of looking at) mental states makes things a little confusing, but it will be useful later on.
http://consc.net/papers/c-and-c.html
