To Florus 4.87

Moreover, the belief in natural sin would not merely destroy the force of imitation; it would expose fraud in the very praise offered to Christ. With what seriousness, with what face, could anyone say that no deceit was found in his mouth? If he had come in a condition of flesh different from ours, he would be proved to have practiced deliberate deceit not only in teaching, which is less serious, but even in being born, which is more serious. What sort of conduct would this be? Human beings would be established in natural evil and the devil’s kingdom, sinning under the deadly necessity of an inborn plague, or naturally serving the law of sin that ruled in their members (compare Romans 7:23). Yet he would force them, even under threat of punishment, to imitate him, and demand his own righteousness from people of a flesh whose evil had terrified him so greatly that, though he wished to display a model of goodness under its appearance, he avoided the reality of its nature. How much more rightly could the sickness of sinners, secure in their claim to be compelled, say to him: “When we are well, we all give sound advice to the sick. If you were in this condition, you would think very, very differently!”

What, then, has your impiety achieved? This necessary consequence: if sin is believed naturally present in our flesh, Christ either assumed that flesh and is liable to its evil, or did not assume it and is bound inescapably by the injustice, not of his birth, which then appears false, but of deliberate deception. All this is so foul with blasphemy that it can scarcely be set out without horror, even while being torn apart. Let the Mediator’s dignity therefore stand by his example and his work, and by our faith. Defending the truth through both his words and his apostle’s, that faith never ceases to proclaim that Christ, a true human being, assumed from Mary’s womb flesh of the same nature as ours. Though a true human being in every respect, he had no sin. To indicate this, it suffices for the apostle Peter to say that he committed no sin, teaching that one who had not committed it could not possess it (compare 1 Peter 2:21–22). No deceit was found in his mouth. He offered a holy example to those sharing his nature, which he himself had made in everyone. Sin is therefore clearly not inborn, since Christ did not have it: without losing the honor of his divinity, he became flesh precisely so that we could imitate him.