How do you mean?
Sight being, as I conceive, in the eyes, and he who has eyes wanting to see; colour being also present in them, still unless there be a third nature specially adapted to the purpose, the owner of the eyes will see nothing and the colours will be invisible.
Of what nature are you speaking?
Of that which you term light, I replied.
True, he said.
Noble, then, is the bond which links together sight and visibility, and great beyond other bonds by no small difference of nature; for light is their bond, and light is no ignoble thing?
Nay, he said, the reverse of ignoble.
And which, I said, of the gods in heaven would you say was the lord of this element? Whose is that light which makes the eye to see perfectly and the visible to appear?
You mean the sun, as you and all mankind say.
May not the relation of sight to this deity be described as follows?
How?
Neither sight nor the eye in which sight resides is the sun?
No.
Yet of all the organs of sense the eye is the most like the sun?
By far the most like.
And the power which the eye possesses is a sort of effluence which is dispensed from the sun?
Exactly.
Then the sun is not sight, but the author of sight who is recognised by sight?
True, he said.
And this is he whom I call the child of the good, whom the good begat in his own likeness, to be in the visible world, in relation to sight and the things of sight, what the good is in the intellectual world in relation to mind and the things of mind:
Will you be a little more explicit? he said.
Why, you know, I said, that the eyes, when a person directs them towards objects on which the light of day is no longer shining, but the moon and stars only, see dimly, and are nearly blind; they seem to have no clearness of vision in them?
Very true.
But when they are directed towards objects on which the sun shines, they see clearly and there is sight in them?
Certainly.