Nicene and Post-Nicene Fathers, Vol. II:
City of God: Chapter 27

Chapter 27.—Of the Angels and Men Who Sinned, and that Their Wickedness Did Not Disturb the Order of God’s Providence.

The sins of men and angels do nothing to impede the “great works of the Lord which accomplish His will.” 762   For He who by His providence and omnipotence distributes to every one his own portion, is able to make good use not only of the good, but also of the wicked.  And thus making a good use of the wicked angel, who, in punishment of his first wicked volition, was doomed to an obduracy that prevents him now from willing any good, why should not God have permitted him to tempt the first man, who had been created upright, that is to say, with a good will?  For he had been so constituted, that if he looked to God for help, man’s goodness should defeat the angel’s wickedness; but if by proud self-pleasing he abandoned God, his Creator and Sustainer, he should be conquered.  If his will remained upright, through leaning on God’s help, he should be rewarded; if it became wicked, by forsaking God, he should be punished.  But even this trusting in God’s help could not itself be accomplished without God’s help, although man had it in his own power to relinquish the benefits of divine grace by pleasing himself.  For as it is not in our power to live in this world without sustaining ourselves by food, while it is in our power to refuse this nourishment and cease to live, as those do who kill themselves, so it was not in man’s power, even in Paradise, to live as he ought without God’s help; but it was in his power to live wickedly, though thus he should cut short his happiness, and incur very just punishment.  Since, then, God was not ignorant that man would fall, why should He not have suffered him to be tempted by an angel who hated and envied him?  It was not, indeed, that He was unaware that he should be conquered. but because He foresaw that by the man’s seed, aided by divine grace, this same devil himself should be conquered, to the greater glory of the saints.  All was brought about in such a manner, that neither did any future event escape God’s foreknowledge, nor did His foreknowledge compel any one to sin, and so as to demonstrate in the experience of the intelligent creation, human and angelic, how great a difference there is between the private presumption of the creature and the Creator’s protection.  For who will dare to believe or say that it was not in God’s power to prevent both angels and men from sinning?  But God preferred to leave this in their power, and thus to show both what evil could be wrought by their pride, and what good by His grace.

Footnotes

Ps. 111.2.