Defining "Consciousness"
Scientists, students, ordinary folks, and even philosophers sometimes find the word "consciousness" baffling or suspicious. Understandably, they want a definition. To the embarrassment of us in "consciousness studies", it proves surprisingly difficult to give one. Why? The reason is this: The two most respectable avenues for scientific definition are both blocked in the case of consciousness.
Analytic definitions break a concept into more basic parts: A "bachelor" is a marriageable but unmarried man. A "triangle" is a closed, three-sided planar figure. In the case of consciousness, analytic definition is impossible because consciousness is already a basic concept. It's not a concept that can be analyzed in terms of something else. One can give synonyms ("stream of experience", "qualia", "phenomenology") but synonyms are not scientifically satisfying in the way analytic definitions are.
Functional definitions characterize terms by means of their causal role: A "heart" is the primary organ for pumping blood; "currency" is whatever serves as the medium of exchange. Someday maybe a functional definition of consciousness will be possible; but first we have to know what kind of causal role (if any) conscious plays; and we're a long way from knowing this. Various philosophers and psychologists have theories, of course, but to define consciousness in terms of one of these contentious theories begs the question.
So maybe the best we can do is definition by instance and counterinstance: "Furniture" includes these things (tables, desks, chairs, beds) and not these (doors, toys, clothes). "Square" refers to these shapes and not these. Hopefully with enough instances and counterinstances one begins to get the idea. So also with consciousness: Consciousness includes inner speech; visual imagery; felt emotions; dreams; hallucinations; vivid visual, auditory, and other sensations. It does not include: Immune system response, early visual processing, myelination of the axons; what goes on in dreamless sleep.
Unfortunately, definition by instance and counterinstance leaves unclear what to do about cases that don't obviously fit with either the given instances or counterinstances: If all the given instances and counterinstances of "square" are in Euclidean space, what does one do with non-Euclidean figures? Are paintings "furniture"?
Now of course some cases are just vague and rightly remain so. But one question that interests me turns on exactly the kinds of cases that definition of consciousness by instance and counterinstance leaves unclear: Whether unattended or peripheral stimuli (the hum of the refrigerator in the background when you're not thinking about it, the feeling of your feet in your shoes) are conscious. It would beg the question to include such cases in one's instances or counterinstances. But this class of potential instances is so large and important that to ignore it risks leaving unclear exactly what sort of phenomenon "consciousness" is.
Now maybe (this is my hope) there really is just one property -- what consciousness researchers call "consciousness" -- that stands out as the obvious referent of any term meant to fit the instances and counterinstances above, so that no human would accidentally glom on to another property, given the definition, just as no human would glom on to "undetached rabbit part" as the referent of the term "rabbit" used in the normal way. But this may not be true; and if it's also not acceptable (as I think it's not) simply to lump cases like the sound of the fridge and the feeling of one's shoes into the class of vague, in-between cases, then even definition by instance and counterinstance fails as a means of characterizing consciousness.
Are we left then with Ned Block's paraphrase of Louis Armstrong: "If you got to ask [what consciousness/jazz is], you ain't never gonna get to know"?