9. All these so-called proofs were invalidated by Immanuel Kant, the great philosopher of Königsberg, whose critical inquiry into the human intellect showed that the entire sum of our knowledge of objects and also of the formulation of our ideas is based upon our limited mode of apperception, while the reality or essence, “the thing in itself,” will ever remain beyond our ken. If this is true of physical objects, it is all the more true of God, whom we know through our minds alone and not at all through our five senses. Accordingly, he shows that all the metaphysical arguments have no basis, and that we can know God’s existence only through _ethics_, as a postulate of our moral nature. The inner consciousness of our moral obligation, or duty, implies a moral order of life, or moral law; and this, in turn, postulates the existence of God, the Ruler of life, who assigns to each of us his task and his destiny.(171) 10. It is true that God is felt and worshiped first as the supreme power in the world, before man perceives Him as the highest ideal of morality. Therefore man will never cease looking about him for vestiges of divinity and for proofs of his intuitive knowledge of God. The wondrous order, harmony, and signs of design in nature, as well as the impulse of the reason to search for the unity of all things, corroborate this innate belief in God. Still more do the consciousness of duty in the individual—conscience—and the progress of history with its repeated vindication of right and defeat of wrong proclaim to the believer unmistakably that the God of justice reigns. But no proof, however convincing, will ever bring back to the skeptic or unbeliever the God he has lost, unless his pangs of anguish or the void within fill his desolate world anew with the vivifying thought of a living God. 11. Among all the Jewish religious philosophers the highest rank must be accorded to Jehudah ha Levi, the author of the _Cuzari_,(172) who makes the historical fact of the divine revelation the foundation of the Jewish religion and the chief testimony of the existence of God. As a matter of fact, reason alone will not lead to God, except where religious intuition forms, so to speak, the ladder of heaven, leading to the realm of the unknowable. Philosophy, at best, can only demonstrate the existence of a final Cause, or of a supreme Intelligence working toward sublime purposes; possibly also a moral government of the world, in both the physical and the spiritual life. Religion alone, founded upon divine revelation, can teach man to find a God, to whom he can appeal in trust in his moments of trouble or of woe, and whose will he can see in the dictates of conscience and the destiny of nations. Reason must serve as a _corrective_ for the contents of revelation, scrutinizing and purifying, deepening and spiritualizing ever anew the truths received through intuition, but it can never be the final source of truth.