Republic (6.508)

The bond, then, that yokes together visibility and the faculty of sight is more precious by no slight form[*] than that which unites the other pairs, if light is not without honor.It surely is far from being so, he said. Which one can you name of the divinities in heaven[*] as the author and cause of this, whose light makes our vision see best and visible things to be seen? Why, the one that you too and other people mean, he said; for your question evidently refers to the sun.[*] Is not this, then, the relation of vision to that divinity? What? Neither vision itself nor its vehicle, which we call the eye, is identical with the sun. Why, no. But it is, I think, the most sunlike[*] of all the instruments of sense. By far the most. And does it not receive the power which it possesses as an influx, as it were, dispensed from the sun? Certainly. Is it not also true that the sun is not vision, yet as being the cause thereof is beheld by vision itself? That is so, he said. This, then, you must understand that I meant by the offspring of the good[*] which the good begot to stand in a proportion[*] with itself: as the good is in the intelligible region to reason and the objects of reason, so is this in the visible world to vision and the objects of vision. How is that? he said; explain further. You are aware, I said, that when the eyes are no longer turned upon objects upon whose colors the light of day falls but that of the dim luminaries of night, their edge is blunted and they appear almost blind, as if pure vision did not dwell in them. Yes, indeed, he said. But when, I take it, they are directed upon objects illumined by the sun, they see clearly, and vision appears to reside in these same eyes. Certainly. Apply this comparison to the soul also in this way. When it is firmly fixed on the domain where truth and reality shine resplendent[*] it apprehends and knows them and appears to possess reason; but when it inclines to that region which is mingled with darkness, the world of becoming and passing away, it opines only and its edge is blunted, and it shifts its opinions hither and thither, and again seems as if it lacked reason. Yes, it does, This reality, then, that gives their truth to the objects of knowledge and the power of knowing to the knower, you must say is the idea[*] of good, and you must conceive it as being the cause of knowledge, and of truth in so far as known.[*] Yet fair as they both are, knowledge and truth, in supposing it to be something fairer still[*] than these you will think rightly of it.