Plato, Phaedo

[70a] the other things you say, but in regard to the soul men are very prone to disbelief. They fear that when the soul leaves the body it no longer exists anywhere, and that on the day when the man dies it is destroyed and perishes, and when it leaves the body and departs from it, straightway it flies away and is no longer anywhere, scattering like a breath or smoke. If it exists anywhere by itself as a unit, freed from these evils which you have enumerated just now, [70b] there would be good reason for the blessed hope, Socrates, that what you say is true. But perhaps no little argument and proof is required to show that when a man is dead the soul still exists and has any power and intelligence.”

“What you say, Cebes, is true,” said Socrates. “Now what shall we do? Do you wish to keep on conversing about this to see whether it is probable or not?”

“I do,” said Cebes. “I should like to hear what you think about it.”

“Well,” said Socrates, “I do not believe anyone who heard us now, [70c] even if he were a comic poet, would say that I am chattering and talking about things which do not concern me. So if you like, let us examine the matter to the end.

“Let us consider it by asking whether the souls of men who have died are in the nether world or not. There is an ancient tradition, which we remember, that they go there from here and come back here again and are born from the dead. Now if this is true, if the living are born again from the dead, our souls would exist there, [70d] would they not? For they could not be born again if they did not exist, and this would be a sufficient proof that they exist, if it should really be made evident that the living are born only from the dead. But if this is not so then some other argument would be needed.”

“Certainly,” said Cebes.

“Now,” said he, “if you wish to find this out easily, do not consider the question with regard to men only, but with regard to all animals and plants, and, in short, to all things which may be said to have birth. Let us see with regard to all these, whether it is true that they are all born or generated [70e] only from their opposites, in case they have opposites, as for instance, the noble is the opposite of the disgraceful, the just of the unjust, and there are countless other similar pairs. Let us consider the question whether it is inevitable that everything which has an opposite be generated from its opposite and from it only. For instance, when anything becomes greater it must inevitably have been smaller and then have become greater.”

“Yes.”

“And if it becomes smaller,