According to the positivist view, man is a very complicated organism which has developed, by the way of evolution, from the simplest organism and is capable of reacting in a very complicated manner to external impressions. This capacity for reaction in man is so complicated, and the answering movements may be so remote from the causes which called them forth and conditioned them, that a man’s actions, or at least a part of them, seem to a naive observer to be quite spontaneous and independent.
As a matter of fact, man is not capable of even the smallest independent or spontaneous action. The whole of him is nothing but the result of external influences. Man is a process, a transmitting station of forces. If we imagine a man deprived from his birth of all impressions, and by some miracle having preserved his life, such a man would not be capable of a single action or movement. In actual fact he could not live, as he could neither breathe nor feed. Life is a very complicated series of actions—breathing, feeding, interchange of matters, growth of cells and tissues, reflexes, nervous impulses and so on.
A man lacking external impressions could not have any of these things, and of course he could not show those manifestations, those actions which are usually regarded as of the will and consciousness. ~ G