It was not mathematics that he selected to aid him in his search for the real, for whatever the subtleties of that science may be, it is still too superficial to contain an explorable depth. The natural sciences could aid him as little. Anatomy, botany, and zoölogy reveal, it is true, an infinite variety of forms, but these forms at best are but unrelated perceptions, a series of indecipherable hieroglyphics. Even etiology, when embracing the whole range of physical science, gives at most but the nomenclature, succession, and changes of inexplicable forces, without revealing anything of their inner nature. All these methods were smitten with the same defect,--they were all external, and offered not the essence of things, but only their image and description. To employ them, therefore, in a search for truth would, he said, be on a par with a man who, wandering about a castle looking vainly for the entrance, takes meanwhile a sketch of the façade. Such, however, he noted, is the method which all other philosophers have followed. He concluded, therefore, as man was not only a thinking being, to whom the world was merely an idea, but an individual riveted to the earth by a body whose affections were the starting-point of his intuitions, that reality would come to him, not from without, but from within. "For this body of man's is," he argued, "but an object among other objects; its movements and actions are unknown to the thinking being save as are the changes of the others, and they would be as incomprehensible to him as his own were not their signification revealed to him in another manner. He would see movements follow motives with the constancy of a natural law, and would as little understand the influence of the motive as the connection of any other effect with its cause. He could, if he chose, call it force, quality, or character, but that is all that he would know about it." What, then, is the interior essence of every manifestation and of every action? What is that which is identical with the body to such an extent that to its command a movement always answers? What is that with which Nature plays, which works dumbly in the rock, slumbers in the plant, and awakes in man? Schopenhauer answers with a word, "Will." Will, he teaches, is a force, and should not be taken, as it is ordinarily, to mean simply the conscious act of an intelligent being. In Nature it is a blind, unconscious power; in man it is the foundation of being.