What was ever great in a short time? The whole life period of a man 60-70 yrs is surely but a little thing in comparison with eternity. And should an immortal being seriously think of this little space rather than of the whole? Certainly, an immortal being think of the whole. So, the soul of man is immortal and imperishable & it’s not hard to prove.
There is a thing which we call good and another which we call evil. You will be agree with me in thinking that the corrupting and destroying element is the evil, and the saving and improving element the good. And we will admit that everything has a good and also an evil; as ophthalmia is the evil of the eyes and disease of the whole body; as mildew is of corn, and rot of timber, or rust of copper and iron: in everything, or in almost everything, there is an inherent evil and disease.
And anything which is infected by any of these evils is made evil, and at last wholly dissolves and dies. The vice and evil which is inherent in each is the destruction of each; and if this does not destroy them there is nothing else that will; for good certainly will not destroy them, nor again, that which is neither good nor evil. If, then, we find any nature which having this inherent corruption cannot be dissolved or destroyed, we may be certain that of such a nature there is no destruction.
In case of Soul, there are evils and those are unrighteousness, intemperance, cowardice, ignorance. But does any of these dissolve or destroy her? -and here we do not fall into the error of supposing that the unjust and foolish man, when he is detected, perishes through his own injustice, which is an evil of the soul.
Taking in consideration the analogy of the body, the evil of the body is a disease which wastes and reduces and annihilates the body; and all the things of which we were just now speaking come to annihilation through their own corruption attaching to them and inhering in them and so destroying them.
Now, we will consider the soul in like manner. We can say, the injustice or other evil which exists in the soul can’t waste and consume her. They can’t by attaching to the soul and inhering in her at last bring her to death and so separate her from the body.
And yet, it is unreasonable to suppose that anything can perish from without through affection of external evil which could not be destroyed from within by a corruption of its own.
Again Consider, that even the badness of food, whether staleness, decomposition, or any other bad quality, when confined to the actual food, is not supposed to destroy the body; although, if the badness of food communicates corruption to the body, then we should say that the body has been destroyed by a corruption of itself, which is disease, brought on by this; but that the body, being one thing, can be destroyed by the badness of food, which is another, and which does not engender any natural infection -this we shall absolutely deny.
And, on the same principle, unless some bodily evil can produce an evil of the soul, we must not suppose that the soul, which is one thing, can be dissolved by any merely external evil which belongs to another.
Either then, let us refute this conclusion, or, while it remains unrefuted, let us never say that fever, or any other disease, or the knife put to the throat, or even the cutting up of the whole body into the minutest pieces, can destroy the soul, until she herself is proved to become more unholy or unrighteous in consequence of these things being done to the body; but that the soul, or anything else if not destroyed by an internal evil, can be destroyed by an external one, is not to be affirmed by any man.
And surely, no one will ever prove that the souls of men become more unjust in consequence of death. But if someone who would rather not admit the immortality of the soul boldly denies this, and says that the dying do really become more evil and unrighteous, then, if the speaker is right, I suppose that injustice, like disease, must be assumed to be fatal to the unjust, and that those who take this disorder die by the natural inherent power of destruction which evil has, and which kills them sooner or later, but in quite another way from that in which, at present, the wicked receive death at the hands of others as the penalty of their deeds.
And in that case injustice, if fatal to the unjust, will not be so very terrible to him, for he will be delivered from evil. But I rather suspect the opposite to be the truth, and that injustice which, if it have the power, will murder others, keeps the murderer alive --aye, and well awake too; so far removed is her dwelling-place from being a house of death.
So, if the inherent natural vice or evil of the soul is unable to kill or destroy her, hardly will that which is appointed to be the destruction of some other body, destroy a soul or anything else except that of which it was appointed to be the destruction.
But the soul which cannot be destroyed by an evil, whether inherent or external, must exist for ever, and if existing forever, must be immortal.
That is the conclusion, and, if a true conclusion, then the souls must always be the same, for if none be destroyed they will not diminish in number. Neither will they increase, for the increase of the immortal natures must come from something mortal, and all things would thus end in immortality.
Source: The Republic by Plato (360 BCE); Translated-Benjamin Jowett.