Socrates, having thus satisfactorily answered the argument adduced by Simmias, goes on to rebut that of Cebes,[21] who objected that the soul might in time wear out. In order to do this, he relates that, when a young man, he attempted to investigate the causes of all things, why they exist and why they perish; and in the course of his researches, finding the futility of attributing the existence of things to what are called natural causes, he resolved on endeavoring to find out the reasons of things. He therefore assumed that there are a certain abstract beauty and goodness and magnitude, and so of all other things; the truth of which being granted, he thinks he shall be able to prove that the soul is immortal.
This, then, being conceded by Cebes, Socrates[22] argues that every thing that is beautiful is so from partaking of abstract beauty, and great from partaking of magnitude, and little from partaking of littleness. Now, it is impossible, he argues, that contraries can exist in the same thing at the same time; for instance, the same thing can not possess both magnitude and littleness, but one will withdraw at the approach of the other; and not only so, but things which, though not contrary to each other, yet always contain contraries within themselves, can not co-exist; for instance, the number three has no contrary, yet it contains within itself the idea of odd, which is the contrary of even, and so three never can become even; in like manner, heat while it is heat can never admit the idea of its contrary, cold. Now, if this method of reasoning is applied to the soul, it will be found to be immortal; for life and death are contraries, and never can co-exist; but wherever the soul is, there is life: so that it contains within itself that which is contrary to death, and consequently can never admit of death; therefore it is immortal.
With this he closes his arguments in support of the soul's immortality. Cebes owns himself convinced, but Simmias, though he is unable to make any objection to the soundness of Socrates's reasoning, can not help still entertaining doubts on the subject. If, however, the soul is immortal, Socrates proceeds,[23] great need is there in this life to endeavor to become as wise and good as possible. For if death were a deliverance from every thing, it would be a great gain for the wicked; but since the soul appears to be immortal, it must go to the place suited to its nature. For it is said that each person's demon conducts him to a place where he receives sentence according to his deserts.