Consciousness Has an Object and a Subject
Consciousness is a relationship between a subject (the organism possesing the faculty of consciousness) and an object (that which the organism is aware of). In other words, being conscious always involves being conscious of something. This basic idea underpins the characteristics of awareness.
Awareness begs the question, awareness of what? Awareness implies an object of awareness. You can’t see without seeing something, nor can you think without thinking about something. Every act of awareness is directed towards an object, be it concrete or abstract.
Every state of awareness involves some content. Awareness is, by definition, awareness of something. A contentless state of consciousness is a contradiction in terms. [1]
Even when imagining something that doesn’t exist, like a golden mountain, there is still conscious content. You’re not imagining a nothing; you're imagining a golden mountain, to imagine a golden mountain is to imagine that, not something else. The materials used in imagination come from one’s past perception of reality, here of golden qualia and of mountains; you can't imagine qualities you haven't experienced. Imagination is the ability to mentally combine and rearrange such materials. Imagination, in stark contrast to perception, is under direct volitional control: you can visualize whatever you like, but you can see only what is there to be seen.
For instance, you can't visualize ultraviolet light because it's beyond human visual perception. Similarly, those blind from birth don’t have visual imaginations, they cannot even remember shapes without having to recall the feeling of particular objects in their hands. Imagination uses perceptual data stored in memory. Imagining a friend’s face feels much like remembering it, because imagination is about reconfiguring stored perceptions.
Consciousness also necessitates a subject—the being that is aware. When forming the concept of "consciousness," one reflects on personal mental actions (seeing, hearing, thinking, etc.) and integrates these with similar activities observed in other men. Though we can't directly experience another's consciousness, we infer it by analogy to our own experiences.
Philosophers like David Hume questioned how we become aware of the self, saying that introspection only reveals concrete mental acts, not a "self". The response is that it's you who is introspecting, observing your consciousness in action. We don’t first discover general consciousness and then attach it to a person; instead, we start with our own consciousness and recognize similar actions in others.
Rand summarizes:
Existence exists — and understanding this statement implies two corollary axioms: something exists (the object) which one perceives, and one exists (the subject) who perceives. Consciousness is the faculty of perceiving that which exists. Without something to be conscious of, there can be no consciousness. [2]