"Consciousness" denotes both a faculty and a state.
As a faculty, "consciousness" means: the attribute of certain living organisms which enables them to be aware of
existence. (I use "faculty" in the Aristotelian sense, to designate a power or ability.)
As a state, "consciousness" is: awareness—the condition of an organism in cognizing, perceiving, or sensing.
The concept of consciousness as a state, the state of awareness, is a primary; it cannot be broken down any further
or defined by reference to other concepts; there are no other concepts to which it can be reduced. It is the basic
psychological concept and category to which all other psychological terms ultimately must refer; only in the
context of the phenomenon of awareness as one's root concept can such concepts as "thought," "idea," "perception,"
"imagination,'' "memory," "emotion," or "desire" be intelligible. One can investigate the structural and functional
conditions in an organism that are necessary for the existence of consciousness; one can inquire into the
neurophysiological means of consciousness (such as sensory receptors, afferent nerves, etc.); one can differentiate
levels and forms of consciousness. But the concept of consciousness as such is an irreducible primary.
It is what Ayn Rand has termed an "axiomatic concept." She writes:
Axioms are usually considered to be propositions identifying a fundamental, self-evident truth. But explicit propositions as such
are not primaries: they are made of concepts. The base of man's knowledge—of all other concepts, all axioms, propositions and
thought—consists of axiomatic concepts.
An axiomatic concept is the identification of a primary fact of reality, which cannot be analyzed, i.e., reduced to other facts or
broken into component parts.... It is the fundamentally given and directly perceived or experienced, which requires no proof or
explanation, but on which all proofs and explanations rest.
The first and primary axiomatic concepts are "existence," "identity" (which is a corollary of "existence") and "consciousness."
One can study what exists and how consciousness functions; but one cannot analyze (or "prove") existence as such, or
consciousness as such. These are irreducible primaries. (An attempt to "prove" them is self-contradictory: it is an attempt to
"prove" existence by means of non-existence, and consciousness by means of unconsciousness).^1