[157] Now the nature of light is twofold: for there is one light which proceeds from the fire which we use, a perishable light proceeding from a perishable material, and one which admits of being extinguished. But the other kind is inextinguishable and imperishable, descending to us from above from heaven, as if every one of the stars was pouring down its beams upon us from an everlasting spring. And the sense of sight associates with each of these kinds of light, and through the medium of both of them does it approach the objects of sight so as to arrive at a most accurate comprehension of them.