Reason is the faculty that identifies and integrates the material provided by man’s senses. It is a faculty that man has to exercise by choice. Thinking is not an automatic function. In any hour and issue of his life, man is free to think or to evade that effort. Thinking requires a state of full, focused awareness. The act of focusing one’s consciousness is volitional. Man can focus his mind to a full, active, purposefully directed awareness of reality—or he can unfocus it and let himself drift in a semiconscious daze, merely reacting to any chance stimulus of the immediate moment, at the mercy of his undirected sensory-perceptual mechanism and of any random, associational connections it might happen to make.

Ayn Rand