Phaedo - P:81

Will the soul, the invisible art which makes its way to a region of the same kind, noble and pure and invisible, to Hades in fact, to the good and wise god whither, god willing, my soul must soon be going -- will the soul, being of this kind and nature, be scattered and destroyed on leaving the body, as the majority of men say? Far from it, my dear Cebes and Simmias, but what happens is much more like this: if it is pure when it leaves the body and drags nothing bodily with it, as it had no willing association with the body in life, but avoided it and gathered itself together by itself and always practised this, which is no other than practising philosophy in the right way, in fact, training to die easily. Or is this not training for death?

It surely is.

A soul in this state makes its way to the invisible, which is like itself, the divine and immortal and wise, and arriving there it can be happy, having rid itself of confusion, ignorance, fear, violent desires and the other human ills and, as is said of the initiates, truly spend the rest of time with the gods. Shall we say this, Cebes, or something different?

This, by Zeus, said Cebes.

But I think that if the soul is polluted and impure when it leaves the body, having always been associated with it and served it, bewitched by physical desires and pleasures to the point at which nothing seems to exist for it but the physical, which one can touch and see or eat and drink or make use of for sexual enjoyment, and if that soul is accustomed to hate and fear and avoid that which is dim and invisible to the eyes but intelligible and to be grasped by philosophy -- do you think such a soul will escape pure and by itself?

Impossible, he said.

It is no doubt permeated by the physical, which constant intercourse and association with the body, as well as considerable practice, has caused to become ingrained in it?

Quite so.

We must believe, my friend, that this bodily element is heavy, ponderous, earthy and visible. Through it, such a soul has become heavy and is dragged back to the visible region in fear of the unseen and of Hades. It wanders, as we are told, around graves and monuments, where shadowy phantoms, images that such souls produce, have been seen, souls that have not been freed and purified but share in the visible, and are therefore seen.

That is likely Socrates.