Socrates: …The realm revealed by sight corresponds to the prison, and the light of the fire in the prison to the power of the sun. And you won’t go wrong if you connect the ascent into the upper world and the sight of the objects there with the upward progress of the mind into the intelligible region. That, at any rate, is my interpretation, which is what you are anxious to hear. The truth of the matter is known only to god. But in my opinion, for what it is worth, the final thing to be perceived in the intelligible region, and perceived only after much difficulty, is the form of the good. Once one has seen it, one infers that it is the cause of whatever is right and valuable in anything, that in the visible realm it produces both light its source, and that in the intelligible region itself controls and provides truth and understanding. And anyone who is going to act rationally either in public or private life must have sight of it.
Glaucon: I agree, so far as I am able to understand.
Socrates: Then you will perhaps also agree with me that it won’t be surprising if those who get so far are unwilling to involve themselves in human affairs, and if their minds long to remain in the realm above. That is surely what we should expect if our analogy [of the prisoners in the cave] holds.
Glaucon: Yes, that’s to be expected.
Socrates: Nor will you think it strange that anyone who descends from contemplation of the divine to human life and its ills should blunder and make a fool of himself, if, while still blinded and unaccustomed to the surrounding darkness, he’s forcibly put on trial in the law-courts or elsewhere about the shadows of justice or the figures of which they are shadows, and made to dispute about the notions of them held by men who have never seen justice itself?
Glaucon: There is nothing strange in that.
Socrates: Anyone with any sense would remember that there are two kinds of disturbances of the eyes, caused either from coming out of the light or from going into the light, which is as true for the mind’s eyes as it is for the bodily eyes. He who remembers this when he sees anyone whose vision is perplexed and weak, will not readily laugh, but instead ask whether the soul of that person had come out of the brighter life and is unable to see because they are unaccustomed to the dark, or, having turned from darkness to the day, is dazzled by the excess of light. And he will count the one happy in his condition and state of being, and he will pity the other. If one laughs at the soul which comes from below and into the light, there will be more reason in them than in the one who laughs the one who returns from above out of the light and into the cave.
Prometheus Unbound 