 An important distinction separates access consciousness from phenomenal consciousness (Block 1995). “Phenomenal consciousness” refers to those properties of experience that correspond to what it is like for a subject to have those experiences (Nagel 1974 and the entry on  qualia).  These features are apparent to the subject from the inside, so tracking them arguably depends on one’s having the relevant experience. For example, one understands what it is like to see red only if one has visual experiences of the relevant type (Jackson 1982).