Augustine of Hippo

If you did not wish to be contentious, I think you would now see how correctly we understand what you are trying to explain differently. When the prophet said, "who forgives all your faults"—something that is done by the remission of all sins—he immediately added "who heals all your diseases." He wants us to understand the evils with which the saints will never finish their internal warfare until those evils are healed or, as far as possible in this life, progressively diminished. Not even when the virtue of chastity stands unshaken is there no sickness by which the flesh lusts against the spirit. When there is no sickness, the spirit does not lust against it, because it lusts in order at least by not consenting to obtain health, since it is unable to do so by not fighting. We are speaking of that whose resistance to us we perceive within us; if an alien nature, we must get rid of it; if our own, it must be healed. If we say it is an alien nature and must be gotten rid of, we agree with the Manichaeans. Let us, then, confess it is our own nature that must be healed, and thus we shall at the same time be clear of Manichaeans and Pelagians.