A Treatise on Nature and Grace 76
76 John of Constantinople PL 44, 285
He quotes also John, bishop of Constantinople, as saying “that sin is not a substance, but a wicked act.” Who denies this? “And because it is not natural, therefore the law was given against it, and because it proceeds from the liberty of our will.” Who, too, denies this? However, the present question concerns our human nature in its corrupted state; it is a further question also concerning that grace of God whereby our nature is healed by the great Physician, Christ, whose remedy it would not need if it were only whole. And yet your author defends it as capable of not sinning, as if it were sound, or as if its freedom of will were self-sufficient.
Idem tractatur argumentum. Item Joannes Constantinopolitanus episcopus cujus posuit sententiam, dicit peccatum non esse substantiam, sed actum malignum: quis hoc negat? Et quia non est naturale, ideo contra illud legem datam, et quod de arbitrii libertate descendit: etiam hoc quis negat? Sed nunc agitur de humana natura quae vitiata est; agitur et de gratia Dei qua sanatur per medicum Christum, quo non indigeret si sana esset, quae ab isto tanquam sana, vel tanquam sibi sufficiente voluntatis arbitrio, posse non peccare defenditur.