The Reason and its three Ideas give what Kant calls transcendent knowledge in distinction from the transcendental knowledge of the understanding and its categories. By transcendent knowledge he means that which is beyond the limits of possible experience; while transcendental knowledge refers to knowledge about the necessary principles of experience. Kant, however, is willing to acknowledge that the Ideas of the Reason have a legitimate use. They are “regulative principles” in that, by showing what our limitations are, they also show that human knowledge is not the final goal. Their illegitimate use appears when they make a show of being true knowledge. Both science and theology will be the gainers when the Ideas are no longer used illegitimately. Kant says that he has destroyed knowledge of God and the soul “in order to make room for faith.” =The Idea of the Soul.= Rational psychology had taught that the soul had direct and intuitive knowledge of itself. From the time when Descartes formulated his famous “_Cogito ergo sum_,” this conception of self-consciousness has been popular. I can have myself as the direct object of my own thought. Upon the basis of such assumed intuitive knowledge that each soul has of itself, the Rationalists had ascribed the qualities of simplicity, substantiality, spirituality, and immortality to the soul. Kant denies that we have any such self-knowledge. If we turn back to his definition of knowledge we find it to be a synthesis of a manifold. Knowledge, to be knowledge, must (1) be based upon sensations, and on that account (2) consist only of phenomena. The soul is not phenomenal, but the deepest kind of reality. How can I have knowledge of my soul? The soul is spiritual and not phenomenal, even according to the Rationalistic philosophy. Therefore the soul is precluded from being an object of knowledge. Furthermore the Rationalists’ conception of the soul as simple and immortal would make it an impossible object of knowledge. An object of knowledge is not simple, but is the unity of a manifold. The unifying or synthesizing function is not an object to itself. Sensations are synthesized by space and time into perceptions; but space and time are not objects for the sensations. In understanding, therefore, the “I think,” which synthesizes the perceptions into judgment, cannot be an object for the understanding. Kant points out that we must be careful to distinguish between the transcendental and the empirical ego. We have referred to this distinction already. In Kant’s criticism of knowledge he maintained that there must be postulated a “synthetic unity of apperception,” if knowledge is possible. But such an ego is only a postulate; we can have no knowledge of it nor can we say what it is. We know that the immediacy of experience or the sameness of knowledge from moment to moment demands this. This is the transcendental ego, a kind of universal synthetic background.