But the Orphic-Pythagorean confidence in the immortality of the soul was at the most only an emotional belief. It remained for Plato in the early fourth century to give that belief a philosophic basis and thereby to transform it into a reasonable article of religion. This he fundamentally did, when he brought his concept of the reasoning soul into connection with his doctrine of “forms” or “ideas.” He maintained that behind this transient phenomenal world known to us through the senses, lies another world, the world of ideas, invisible, permanent, and real, which can be grasped by the reason only. These permanent ideas, he said, are of various grades and degrees, the supreme idea being that of the Good and the Beautiful, which is the cause of all existence, truth, and knowledge; it at once comprehends these things within itself and is superior to them; it is the Absolute, God.[10] But all the ideas, including the Absolute, are, as I have just said, apprehended not by man’s senses but by his intellect. Therefore, argues Plato, man’s reasoning soul must have the same nature as the ideas; like them, it must belong to the world above the senses and with them it must partake of the Absolute. Moreover, since the ideas are eternal and immortal, it inevitably follows that man’s reasoning soul has existed from eternity and will exist forever.[11] This is not the occasion to discuss the validity of Plato’s doctrine. Aristotle stated, once for all, the fundamental objections to his teacher’s views.[12] But we shall readily grant that, if we accept Plato’s doctrine, his conclusions as to the immortality of the soul may logically follow and that no further evidence is needed to convince us. Yet Plato was not content to let the matter rest on this single argument, for in other dialogues he adduces proofs which do not seem so convincing to us as to their author. He attempts to prove immortality from the self-motion of the soul, again from the dim recollections out of an earlier existence which enable one to recall axiomatic truths or to recognize relations, as in mathematics--things which one has never learned in this present life. On another occasion he argues from the unchanging nature of the soul and from the soul’s superiority to the body. But he seems to have thought the most convincing proof was the fact that the notion of life is inseparable from our concept of the soul; that is, a dead soul is unthinkable. For all these reasons, therefore, he argued that the soul must be immortal.[13]