Book 7, 517a-518b
Then, my dear Glaucon, I said, this entire allegory must be related to what we said before. The region which visibly appears should be likened to the prison-house. The light of the fire within it corresponds to the power of the sun. And you won’t miss my expectation, since you’re eager to hear it, if you compare the ascent and the act of seeing what lies above the cave with the soul’s journey toward the intelligible region. Perhaps a god knows whether this is true. In any case, this is how it appears to me: when it comes to what is known, the last thing to be known, and only with difficulty, is the Form of the Good. But once it is seen, we must conclude that this Form is, in fact, the cause of all that is right and good in everything. In the visible, the Form of the Good produces light and light’s ruler, the sun. In the intelligible, the Form of the Good, itself being ruler, produces truth, intelligence, and whatever else is necessary for anyone to know who intends to act prudently, whether in private or in public.
I agree, he said, as far as I am able to understand you.
Let us agree to this too, I said. Don’t be surprised that those who reach such a point are not willing to concern themselves with human affairs. Instead, their souls are always impelled to spend their time above. This is likely if it aligns with the image I previously described.
Yes, likely.
Do you think it would be surprising, I said, if someone, having transitioned from divine contemplations to human evils, appears unseemly and exceedingly ridiculous? Imagine him, still with dim vision and not yet fully accustomed to the surrounding darkness, compelled to argue in courts or elsewhere about the shadows of justice, or about the objects that make the shadows, engaging in disputes about how these things are conceived by people who have never beheld justice itself.
Anything but surprising, he replied.
If someone were intelligent, I said, he would recall that there are two types of disturbances affecting the eyes. One occurs when transitioning from light to darkness, and the other when moving from darkness to light. Now, if we extend this idea to the soul, whenever we encounter a confused soul struggling to perceive anything clearly, we shouldn’t laugh irrationally. Instead, we should ponder whether this soul, having come from a brighter life, is currently in darkness due to lack of familiarity. Alternatively, perhaps she has moved from a state of greater ignorance to one more enlightened, and the brilliance dazzles her. In such a scenario, we might consider the first soul happy in her condition and life, while feeling compassion for the second. And if we were to laugh at the second, it would be less a scornful laugh than even our amusement at the soul descended from the light above.
That, he said, is a very appropriate distinction.