Consciousness is the abnormal state of a living organism. "Sleeping" (unconsciousness) is the normal state.
In consolidating ideas from various disciplines (evolution, biology, psychology, etc) I had to ask myself, "What is the REASON consciousness exists?" The question originated after I had read a proposal that from an evolutionary standpoint, "sleep" was counter-intuitive as a trait that should survive in an evolving organism. While sleeping (unconscious) an organism is at more risk to danger, for instance from predatory attack. So why would "the need to sleep" have survived an evolutionary process? Wouldn't "constant consciousness" have been a more survivable trait to expect to evolve?
After considerable thought, it seems that consciousness (and the level of it) may have evolved dependant on an organism's need to be "mobile" in it's environment, in order to meet the two basic needs of any organism,,,acquire nutrients to ensure it's own future survival (it needs to "eat"), and to reproduce to ensure the continuation of it's species (it needs to "mate"). It appears to me the more complex the organism has evolved, the more mobile it may need to be to accomplish these two things within it's environment. And a higher level of consciousness it may need to successfully move about within it's environment.
But once it has accomplished these two goals, a return to an unconscious state makes sense...it is the least energy consuming state of an organism. Being conscious and moving around expends much more energy and would not be the preferred state of an organism. Thus, "sleep"...the return to the unconscious "normal" state, would not have been eliminated by evolution. It is the state where the organism can repair itself from any "damage" incurred during consciouness, and then maintain itself at the lowest energy consumption level until the need exits to "eat" or reproduce becomes dominant again, at which point it returns to the abnormal state of consciousness to accomplish those things. The cycle then continues.
Consciousness is the abnormal state.