And reality is not as transparent as the Enlightenment assumed it to be; existence divided by reason leaves a remainder, as Goethe had put it. It was Immanuel Kant who tried to arbitrate between the conflicting tendencies of his age. He was an _Aufklärer_ in so far as he brought reason itself to the bar of reason and sat in judgment upon its claims, and, likewise, in so far as he insisted on the objective validity of physics and mathematics. But he was as much opposed to the pretentiousness of dogmatic metaphysics as to the pusillanimity of scepticism and the _Schwärmerei_ of mysticism. He repudiated the shallow proofs of the existence of God, freedom, and immortality no less emphatically than he rejected materialism with its atheism, fatalism, and hedonism. He tried to save everything worth saving--rational knowledge, modern science, the basal truths of the old metaphysics, and the most precious human values. For the scientific intelligence, so he held, nature and the self are absolutely determined; every physical occurrence and every human act are necessary links in a causal chain. But such knowledge is possible only in the field of phenomena (_Erscheinungen_); through sense-perception and the discursive understanding we cannot reach the inner core of reality; nor can we pierce the veil of appearances by means of intellectual intuitions, mystical visions, feeling, or faith, i.e., through the emotional and instinctive parts of our nature. It is the presence of the moral law or categorical imperative within us that points to a spiritual world beyond the phenomenal causal order and assures us of our freedom, immortality, and God. It is because we possess this deeper source of truth in practical reason that freedom and an ideal kingdom in which purpose reigns are vouchsafed to us, and that we can free ourselves from the mechanism of the natural order. It is moral truth that both sets us free and demonstrates our freedom, and that makes harmony possible between the mechanical theory of science and the teleological conception of philosophy. The scientific understanding would plunge us into determinism and agnosticism; from these, faith in the moral law alone can deliver us. In this sense Kant destroyed knowledge to make room for a rational faith in a supersensible world, to save the independence and dignity of the human self and the spiritual values of his people. In claiming a place for the autonomous personality in what _appeared to be_ a mechanical universe, Kant gave voice to some of the deeper yearnings of the age. The German Enlightenment, the new humanism, mysticism, pietism, and the faith-philosophy were all interested in the human soul, and unwilling to sacrifice it to the demands of a rationalistic science or metaphysics. In seeking to rescue it, the great criticist, piloted by the moral law, steered his course between the rocks of rationalism, sentimentalism, and scepticism. It was his solution of the controversy