Theophilus to Autolycus

On the fourth day the luminaries were made; because God, who possesses foreknowledge, knew the follies of the vain philosophers, that they were going to say, that the things which grow on the earth are produced from the heavenly bodies, so as to exclude God. In order, therefore, that the truth might be obvious, the plants and seeds were produced prior to the heavenly bodies, for what is posterior cannot produce that which is prior. And these contain the pattern and type of a great mystery.

For the sun is a type of God, and the moon of man. And as the sun far surpasses the moon in power and glory, so far does God surpass man. And as the sun remains ever full, never becoming less, so does God always abide perfect, being full of all power, and understanding, and wisdom, and immortality, and all good. But the moon wanes monthly, and in a manner dies, being a type of man; then it is born again, and is crescent, for a pattern of the future resurrection. In like manner also the three days which were before the luminaries, are types of the Trinity, of God, and His Word, and His wisdom. And the fourth is the type of man, who needs light, that so there may be God, the Word, wisdom, man.

Wherefore also on the fourth day the lights were made. The disposition of the stars, too, contains a type of the arrangement and order of the righteous and pious, and of those who keep the law and commandments of God. For the brilliant and bright stars are an imitation of the prophets, and therefore they remain fixed, not declining, nor passing from place to place. And those which hold the second place in brightness, are types of the people of the righteous. And those, again, which change their position, and flee from place to place, which also are called planets, they too are a type of the men who have wandered from God, abandoning His law and commandments.