It is customary to distinguish five forms of consciousness: agent consciousness (which is what we have in mind when we say of an agent that he is “losing consciousness” or “regaining consciousness”), propositional consciousness (which is expressed by the “conscious that” construction), introspective consciousness (which is what we have in mind when we say things like “His affection for me is fully conscious, but his hostility is not”), relational consciousness (which is expressed by the “conscious of” construction), and phenomenal consciousness (which is a property that mental states possess when they have a phenomenological dimension – that is, when they present us with such qualitative characteristics as pain and the taste of oranges).

I will have something to say about all of these forms of consciousness in the present work, though some of them will receive much more attention than others. To be more specific, I will have very little to say about agent consciousness and propositional consciousness, for insofar as the philosophical problems associated with these two forms of consciousness are problems of mind (as opposed to problems associated with agency and problems associated with knowledge), they are reducible to problems that arise in connection with other forms of consciousness. They are not in need of separate treatment. I will have more to say about all of the three remaining forms, but one of them, phenomenal consciousness, will be considered at much greater length than the others.