[156] But the most vital part of the benefit we gain from sight remains now to be told. God made the light to shine upon sight alone of the senses, and light is the best of existing things and was the first to be called good in the sacred books.
[157] Now light has a double nature: one is the effulgence of the fire of common use, perishable as that which produces it and liable to extinction, the other, the unquenchable and imperishable, brought to us from heaven above, where each of the stars pours forth its rays as though from perennial fountains. With each of these the sight is conversant, and through both it strikes upon visible objects so as to apprehend them with all exactness.
[158] Need we still try to expend words in extolling the eyes, when God has set graven in the heaven their true praises, the stars? For with what purpose have the rays of the sun and moon and the other stars, planets or fixed, been made save to serve the action of the eyes and to minister to sight?
[159] And so it is, by using light, the best of gifts, that men contemplate the world’s contents, earth, plants, living creatures, fruits, seas with their tides, rivers spring-fed or winter torrents, various kinds of fountains, some sending up a cold, others a warm, stream, and all the phenomena of the air with their several natures, the different forms of which are so countless that speech can never include them all; above all, heaven, which in truth has been framed as a world within a world, and the divine and hallowed forms which beautify it. Which of the other senses, then, can boast that it ever traverses so great a span?