“There is no term [consciousness] at once so popular and so devoid of standard meaning. How can a term mean anything when it is employed to connote anything and everything, including its own negation? One hears of the object of consciousness and the subject of consciousness, and the union of the two in self-consciousness; of the private consciousness, the social consciousness, and the transcendental consciousness; the inner and the outer, the higher and the lower, the temporal and the eternal consciousness; the activity and the state of consciousness. Then there is consciousness-stuff, and the unconscious consciousness…, and unconscious physical states or subconsciousnss…The list is not complete, but sufficiently amazing. Consciousness comprises everything that is, and indefinitely much more. It is small wonder that the definition of it is little attempted.” ~ psychologist Ralph Barton Perry, 1904, quoted in William Calvin’s The Cerebral Symphony
I’d say that 100 years later the term “consciousness” is still devoid of standard meaning. Some people define it in terms of what-it-is-likeness, others define it in terms of introspection and meta-awareness, and others collapse the distinction between what-it-is-likeness and meta-awareness. Some think consciousness is primitive and shared with all mammals, others thinks its the reserve of apes and humans. For some it is a synonym of “awareness” and others it is a synonym of “self-awareness”. Some just want to abandon the term altogether. Personally, I like the definition of consciousness as an introspective or reflective operation, since I think this is in accord with its original connotation in English. Also, to define it in terms of awareness or what-it-is-likeness is hopeless given those terms are just in need of definition as consciousness itself. Adopting the introspective definition is the only way to ground the meaning of consciousness in terms other than itself or our own introspection of it (which is fraught with difficulties given the methodological limitations of introspection).