The result of this double life is that human serenity which furnishes so vivid a contrast to the lack of reason in the brutes. Reason has won to a wonderful extent the mastery over the animal nature. The climacteric stage of the mere exercise of reason is displayed in Stoicism, an ethical system which aims primarily not at virtue but at happiness, although this theory inculcates that happiness can be attained only through "ataraxia" (inward quietness or peace of mind), while this can only be gained by virtue. In other words, Zeno, the founder of the Stoic theory, sought to lift man up above the reach of pain and misery. But this use of pure reason involves a painful paradox, seeing that for an ultimate way of escape Stoicism is constrained to prescribe suicide. When compared with the Stoic, how different appear the holy conquerors of the world in Christianity, that sublime form of life which presents to us a picture wherein we see blended perfect virtue and supreme suffering. _II.--The World as Will_ We are compelled to further inquiry, because we cannot be satisfied with knowing that we have ideas, and that these are associated with certain laws, the general expression of which is the principle of sufficient reason. We wish to know the significance of our ideas. We ask whether this world is nothing more than a mere idea, not worthy of our notice if it is to pass by us like an empty dream or an airy vision, or whether it is something more substantial. We can surely never arrive at the nature of things from without. No matter how assiduous our researches may be, we can never reach anything beyond images and names. We resemble a man going round a castle seeking vainly for an entrance and sometimes sketching the façades. And yet this is the method followed by all philosophers before me. The truth about man is that he is not a pure knowing subject, not a winged cherub without a material body, contemplating the world from without. For he is himself rooted in that world. That is to say, he finds himself in the world as an _individual_ whose knowledge, which is the essential basis of the whole world as idea, is yet ever communicated through the medium of the body, whose sensations are the starting point of the understanding of that world. His body is for him an idea like every other idea, an object among objects. He only knows its actions as he knows the changes in all other objects, and but for one aid to his understanding of himself he would find this idea and object as strange and incomprehensible as all others. That aid is _will_, which alone furnishes the key to the riddle of himself, solves the problem of his own existence, reveals to him the inner structure and significance of his being, his action, and his movements.