As far as I am concerned here phenomenal character is simply to be defined as what is conscious. To be conscious of something (say the table being in front of me) is to say that I am experiencing a particular phenomenal character, one which leads me to think that there is a table in front of me. And this is not a radical re-understanding of phenomenal character. Phenomenal character, as usually defined, is “what it is like” to have a particular experience. Suppose then that there is some X that is conscious plus some phenomenal character which is “what it is like to experience X”. Since consciousness then consists of two parts we could consider another conscious experience (perhaps not physically realizable in us, but in some possible us) which contains Y in the place of X, but the same phenomenal character of “what it is like to experience X”. Clearly in such a situation a person having that conscious experience would believe that their experience contained X, and not Y, because the experience they are having feels exactly the same as one that they would have were X to be accompanied, appropriately, by that phenomenal character. Clearly then neither X or Y is conscious directly, only the phenomenal character, and so the phenomenal character exhausts consciousness (assuming you don’t think we can be in gross error about our own consciousness).
Obviously then phenomenal character is not simple (without parts), but rather contains information. Consider a particular thought, which may be conscious or unconscious. Obviously the difference is that when it is conscious there is an associated phenomenal character. This phenomenal character then must tell us something about the content of that thought, assuming we can know what we are thinking. If it didn’t then we would be in the dark the first time we had a particular thought, because it would be a phenomenal character we had never experienced before, and thus we would be unable to connect it to any particular thought. Obviously then the phenomenal character must contain some information about what is being thought.
Now some of this information at least correlates with the internal states of whatever is doing the thinking. The question then becomes: is there anything more to phenomenal character than that, and if so, how can we know about it? Given that phenomenal character is complex we can represent each phenomenal character by an ordered pair, P(x,y), where x is the content that correlates to the internal state and y is whatever else there is in the phenomenal character. Now if for each x there is only a single y then all of the phenomenal character is correlated to the internal state. So, putting aside the question of whether all phenomenal character correlates with internal state, we can only know that there are parts of phenomenal character uncorrelated to internal state if we can know that ∀x∃y(P(x,y)∧∀z(P(x,z)→z=y)) is false. Which requires us to be able to find two pairs P(x,y) and P(x,z) and then be able to know that ~(z=y), and that requires us to be able to find a property F such that Fz and ~Fy. And that is harder than it looks. The first response of some philosophers is simply to claim that P(x,y) and P(x,z) differ by feeling different, and that knowing that they feel different is enough to know that y and z aren’t identical. But that is begging the question in the worst sort of way. A P(x,y) pair just is what it feels like to have some experience. So saying that two P(x,y) pairs feel different just is to assert that they are different pairs. And since that is exactly what is under investigation obviously we can’t appeal to it in order to validate the assumption, under pain of circularity. A second common response is to appeal to laws concerning the succession of phenomenal character. P(x,y) ⇒ P(q,t)*, but P(x,z) ⇒ P(q,r)**, it may be argued. Thus y and z participate in different sequences of phenomenal character, and so they aren’t identical. However this too is question begging, because it assumes the falsity of ∀x∃y(P(x,y)∧∀z(P(x,z)→z=y)). But that is again the very thing we are searching for a justification to either assert or deny, and so we cannot assume either its truth or its falsity in that search.
This leaves us with a single viable alternative, to claim that the second component of phenomenal character depends on some feature of the world besides the internal state of whatever doing the thinking. But this implies that we cannot know which phenomenal character we are experiencing without knowing what the world is like first (since it is only their property of depending on different features of the external world that distinguishes two phenomenal pairs such as P(x,y) and P(x,z)) and that is absurd because it is a denial that we have direct access to our own consciousness. And of course it is equally absurd to hold that we cannot in fact know that P(x,y) and P(x,z) are distinct, if we maintain that they actually are distinct, because that implies that the difference is not something we can be conscious of. And since phenomenal character is simply defined as what we are conscious of then that is contradicts the definition of phenomenal character.
Now this argument might seem too strong (this is in fact the best response available). Couldn’t we run exactly the same argument, this time attempting to show that all phenomenal character is identical? After all we couldn’t argue that we know the phenomenal character of experiences to be distinct just because they feel different, that would be to beg the question in this case. But fortunately there is a way out. The way out is to accept that the information contained in the phenomenal character makes a causal difference (which is something that we can only accept given that we accept that the phenomenal character depends only on the internal state). In fact I would like to assert that information in general can be distinguished by the causal role it plays in the system that knows the information, although this claim obviously isn’t necessary here (and in fact may be too strong, given that it could be used to rule out the second component of phenomenal character from the outset, but isn’t it absurd to suppose that we could consciously have information and yet be unable to act on that information, or display any sign that we in fact have it).
* ⇒ is defined to mean: is followed by
** Obviosuly if P(x, a) ⇒ P(q, b) then a phenomenal character pair with first component x is always followed by a phenomenal character with first component q, if it is succeeded by any phenomenal character at all, because the internal state the first component depends on is physical, and the physical world is causally closed.