It is evident that the whole of Plato’s system was the result of an effort to solve the problem of death. Again and again he said that the true philosopher lived only to be ready to die; that being so, he declared it to be childish for men at the last to shrink from what they had so long been making ready for. It was himself that Plato wished to convince of a future life. “I do not seek,” he said, “to persuade all those who are here of the truth of what I say, although to do so would greatly please me; what I aim at is to convince myself. Behold me, dear friend, in pursuit of an argument that, as you see, interests me deeply; if what I say turns out to be true, it is good to have believed it, and if there be nothing after death, at least I have gained this, that while I am still with you, I am not borne down with grief.” The doubt which was only latent in Plato was much more active in some other ancient philosophers. Aristotle[210] at one time admitted that part of the soul was immortal, but that the other part was mortal. The two parts came together at the beginning of a life and separated at its end. Later on, however, Aristotle abandoned this theory of the immortality of the personal consciousness, and argued strongly against the Platonic theory of the immortality of the soul, although, however, he still believed in the indestructibility of the “rational spirit,” an immortal principle. The Stoics still further developed such a conception. They held that besides the individual soul there was a universal soul, a presiding influence in which all others had their being.