But other solutions of the problem seemed possible, and they were tried by philosophers. Berkeley and Malebranche sought a way out of the mechanistic dilemma by abolishing or ignoring the world of matter and sinking nature in the mind of God, while Leibniz endeavored to heal the breach between the new mechanical theory and the old teleological interpretation of reality by means of an idealistic pluralism, reconciling the teachings of modern physical science with classical Greek thought and the spiritual demands of Christianity. And with this compromise many in the age of Enlightenment were content. Reason appeared to have accomplished the task which it had set itself when it cast off the guardianship of the School, and had accomplished it without capitulating to materialism, fatalism, and atheism.
II.
But reason itself was not wholly satisfied with its success. In the face of Hume's vigorous attacks upon the pretensions of rationalism, the question of the validity of scientific and meta- physical knowledge could not be ignored, and account had also to be taken of the protests of the will against encroachments upon its freedom and its moral and religious yearnings. Kant offered a new compromise that would save everything worth saving: rational knowledge, modern science, the basal truths of the old metaphysics, and the most precious human values. His problem was, as one of his contemporaries stated it, "to limit Hume's scepticism, on the one hand, and the old dogmatism, on the other, and to refute and destroy materialism, fatalism, atheism, as well as Schwärmerei and superstition." We can have genuine knowledge, universal and necessary judgments, in physics and mathematics, but such knowledge applies to phenomena only; we cannot know things in themselves in this way. The old a priori metaphysics with its mathematical ideal, the old rational psychology, cosmology, and theology go by the board: there is and can be no scientific proof of the soul, of freedom, of immortality, or of the existence of God. Here the case is given to the sceptics: natural science, that is, mathematics and physics,
