You may well ask at this point why these later philosophers with their desire to know God, should still lay so much emphasis on his transcendence, apparently vying with one another in pushing the Divine beyond the universe, which they still regarded as his creation. Now we have already seen that Plato implied that his material principle was imperfect and thereby the source of evil, and that his Absolute, the supreme Idea, was separate from matter. In the period we are now considering all schools which owed ultimate allegiance to Plato or the Pythagoreans held to a clearly defined dualistic view of the universe. Conscious that the visible, material world is imperfect and full of evil, unstable and decaying, they argued that God cannot be immanent in the world, for if he were, he would be subject to evil, imperfection, and change, whereas we must conceive him to be good, perfect, and unchanging unity. Therefore the motive which prompted all these theologians was their desire to save the unity and perfection of God by removing him from all possible contact with matter, to which some like the Neoplatonists, following Plato, absolutely denied all the attributes of being. And the doctrine of divine transcendence was the more natural for Philo and all who had come under the influence of Jewish thought, since the Old Testament constantly affirms the absolute exaltation and perfection of God. In like manner the doctrine of mediary powers was helped by the Jewish idea of the wisdom of God and the popular post-exilic belief in angels. Yet when the theologians had removed God beyond the confines of the world, beyond all knowledge, they had still to deal with the passionate longing for knowledge of God and for assurance of salvation which was strong in large numbers of the uninstructed, as well as in the philosophic élite. This knowledge and assurance could only be supplied by a belief in the direct revelation of God to man. Such a belief was traditional in the Old Testament; on the Greek side it was fostered by the feeling that the great teachers Pythagoras and Plato were divinely inspired; and in the popular Oriental religions which we shall consider in a later lecture, divine revelation was a fundamental article of faith. But let us return to Plotinus.