21 I have thus shown, to the best of my power, that the God we worship did not abide from eternity in darkness, but is Himself light, and in Him is no darkness at all; and in Himself dwells in light inaccessible; and the brightness of this light is His coeternal wisdom. From what we have said, it appears that God was not taken by surprise by the unexpected appearance of light, but that light owes its existence to Him as its Creator, as its owes its continued existence to His approval.
Neither was God ignorant of the future, but the author of the precept as well as the punisher of disobedience; that by showing His righteous anger against transgression, He might provide a restraint for the time, and a warning for the future. Nor does He ask questions from ignorance, but by His very inquiry declares His judgment. Nor is He curious or timid, but excludes the transgressor from eternal life, which is the just reward of obedience. Nor is He greedy for blood and fat; but by requiring from a carnal people sacrifices, suited to their character, He by certain types prefigures the true sacrifice.
Nor is His jealousy an emotion of pale anxiety, but of quiet benevolence, in desire to keep the soul, which owes chastity to the one true God, from being defiled and prostituted by serving many false gods. Nor is He enraged with a passion similar to human anger, but is angry, not in the sense of desiring vengeance, but in the peculiar sense of giving full effect to the sentence of a righteous retribution. Nor does He destroy thousands of men for trifling offenses, or for nothing, but manifests to the world the benefit to be obtained from fearing Him, by the temporal death of those already mortal.
Nor does He punish the righteous and sinners indiscriminately, but chastises the righteous for their good, in order to perfect them, and gives to sinners the punishment justly due to them. Thus, you Manichæans, do your suspicions lead you astray, when, by misunderstanding our Scriptures, or by hearing bad interpreters, you form a mistaken judgment of Catholics. Hence you leave sound doctrine, and turn to impious fables; and in your perversity and estrangement from the society of saints, you reject the instruction of the New Testament, which, as we have shown, contains statements similar to those which you condemn in the Old Testament. So we are obliged to defend both Testaments against you as well as against the Pagans.
Source: Reply to Faustus the Manichaean (New Advent)