 The notions of consciousness most commonly addressed by philosophers are the following: (1) Conscious awareness of one’s own mental states, and “conscious states” in the particular sense of: states whose subjects are aware of being in them. (2) Introspection and one’s privileged access to the internal character of one’s experience itself. (3) Being in a sensory state that has a distinctive qualitative property, such as the color one experiences in having a visual experience, or the timbre of a heard sound. (4) The phenomenal matter of “what it’s like” for the subject to be in a particular mental state, especially what it is like for that subject to experience a particular qualitative property as in (3). Block (1995) and others have used “phenomenal consciousness” for sense (4), without distinguishing it from sense (3). (A further terminological complication is that some theorists, such as Dretske (1995) and Tye (1995), have used the expression “what it’s like” to mean the qualitative property itself, rather than the present higher-order property of that property. This entry will mainly use “qualitative” to allude to sensory qualities of the sort that figure in (3), and “phenomenal” as applying to “what it’s like.”)