"It is an absolutely vain endeavor to attempt to reconstruct or even comprehend the nature of a human being by simply knowing the forces which have acted upon him. However deeply we should like to penetrate, however close we seem to be drawing to truth, one unknown quantity eludes us: man's primordial energy, his original self, that personality which was given him with the gift of life itself. On it rests man's true freedom; it alone determines his real character."