Plato in the 10th book of his Dialogue called the "Republic" employs an argument to prove the immortality of the soul, so nearly resembling a portion of this treatise that I can scarcely doubt St. Chrysostom had it in his mind. The following is the passage in the Platonic dialogue as rendered in the excellent translation of Messrs. Davies & Vaughan. I omit a few sentences here and there.
"Have you not learned, I asked, that our soul is immortal and never dies?
He looked at me and said in amazement. No really I have not: but can you maintain this doctrine?
Yes as I am an honest man, I replied, and I think you could also. It is quite easy to do it.
Proceed by all means.
So you call one thing good and another evil?
And do we hold the same opinion as to the meaning of two terms?
What opinion do you hold?
I hold that the term evil comprises everything that destroys and corrupts, and the term good everything that preserves and benefits.
So do I.
Again; do you maintain that everything has its evil and its good? Do you say for example that the eyes are liable to the evil of ophthalmia, the entire body to disease, corn to mildew, timber to rot, copper and iron to rust or in other words that almost everything is liable to some connatural evil and malady?
And is it not the case that, whenever an object is attacked by one of these maladies it is impaired; and in the end completely broken up and destroyed by it?
Doubtless it is so?
Hence everything is destroyed by its own connatural evil and vice: otherwise if it be not destroyed by this, there is nothing else that can corrupt it. For that which is good will never destroy anything, nor yet that which is neither good nor evil.
Of course not.
If then we can find among existing things one which is liable to a particular evil which can indeed mar it, but cannot break it up or destroy it, shall we not be at once certain that a thing so constituted can never perish?
That would be a reasonable conclusion.
Well then is not the soul liable to a malady which renders it evil?
Certainly it is: all those things which we were lately discussing -- injustice, intemperance, cowardice, and ignorance -- produce that result."
Then having proved that although these things injure the soul they do not actually destroy it he proceeds.
"Well, it is irrational to suppose that a thing can be destroyed by the depravity of another thing, though it cannot be destroyed by its own.
True it is irrational.
Yes it is: for you must remember that we do not imagine that a body is to be destroyed by the proper depravity of its food whatever that may be, whether mouldiness or rottenness or anything else. But if the depravity of the food itself produces in the body a disorder proper to the body, we shall assert that the body has been destroyed by its food remotely, but by its own proper vice or disease, immediately: and we shall always disclaim the notion that the body can be corrupted by the depravity of its food which is a different thing from the body -- that is to say, the notion that the body can be corrupted by an alien evil without the introduction of its own native evil.
You are perfectly correct.
Then according to the same reasoning I continued, unless depravity of body introduces into the soul depravity of soul let us never suppose that the soul can be destroyed by an alien evil without the presence of its own peculiar disease: for that would be to suppose that one thing can be destroyed by the evil of another thing.
That is a reasonable statement.
Well then let us either refute this doctrine and point out our mistake or else, so long as it remains unrefuted, let us never assert that a fever or any other disease, or fatal violence, or even the act of cutting up the entire body into the smallest possible pieces can have any tendency to destroy the soul, until it has been demonstrated that in consequence of this treatment of the body the soul itself becomes more unjust and more unholy. For so long as a thing is exempt from its own proper evil, while an evil foreign to it appears in another subject, let us not allow it to be said that this thing whether it be a soul or anything else is in danger of being destroyed.
Well, certainly no one will prove that the souls of the dying become more unjust in consequence of death." Here follows a passage to prove that even injustice does not destroy the soul, after which he proceeds,
"Surely then when the soul cannot be killed and destroyed by its own depravity and its own evil, hardly will the evil which is charged with the destruction of another thing destroy a soul or anything else beyond its own appropriate object.
Hardly: at least that is the natural inference.
Hence, as it is destroyed by no evil at all, whether foreign to it or its own, it is clear that the soul must be always existing, and therefore immortal.
If any one will compare this extract with chapters 2 to 6 in the following treatise he cannot fail to be struck by the similarity of thought and language, although in the latter case it is more apparent in the original than it can be in translation. The aim of the two writers is not indeed identical: Chrysostom's object is to prove that nothing can really injure a man except sin -- depravity of soul -- Plato begins by proving this, and proceeds to maintain that if even that which corrupts the soul cannot actually destroy it the soul must be imperishable. They employ the same argument, only Plato carries it a step further than Chrysostom.