Consciousness—for those living organisms which possess it—is the basic means
of survival. For man, the basic means of survival is reason. Man cannot
survive, as animals do, by the guidance of mere percepts. A sensation of hunger
will tell him that he needs food (if he has learned to identify it as
“hunger”), but it will not tell him how to obtain his food and it will not tell
him what food is good for him or poisonous. He cannot provide for his simplest
physical needs without a process of thought. He needs a process of thought to
discover how to plant and grow his food or how to make weapons for hunting. His
percepts might lead him to a cave, if one is available—but to build the
simplest shelter, he needs a process of thought. No percepts and no “instincts”
will tell him how to light a fire, how to weave cloth, how to forge tools, how
to make a wheel, how to make an airplane, how to perform an appendectomy, how
to produce an electric light bulb or an electronic tube or a cyclotron or a box
of matches. Yet his life depends on such knowledge—and only a volitional act
of his consciousness, a process of thought, can provide it.