Augustine of Hippo, On the Spirit and the Letter Chapter 47: The Law ‘Being Done by Nature’ Means, Done by Nature as Restored by Grace

Chapter 47 [XXVII.]—The Law “Being Done by Nature” Means, Done by Nature as Restored by Grace.

Nor ought it to disturb us that the apostle described them as doing that which is contained in the law “by nature,”—not by the Spirit of God, not by faith, not by grace. For it is the Spirit of grace that does it, in order to restore in us the image of God, in which we were naturally created. Sin, indeed, is contrary to nature, and it is grace that heals it,—on which account the prayer is offered to God, “Be merciful unto me: heal my soul; for I have sinned against Thee.” Therefore it is by nature that men do the things which are contained in the law; for they who do not, fail to do so by reason of their sinful defect. In consequence of this sinfulness, the law of God is erased out of their hearts; and therefore, when, the sin being healed, it is written there, the prescriptions of the law are done “by nature,”—not that by nature grace is denied, but rather by grace nature is repaired. For “by one man sin entered into the world, and death by sin, and so death passed upon all men; in which all have sinned;” wherefore “there is no difference: they all come short of the glory of God, being justified freely by His grace.” By this grace there is written on the renewed inner man that righteousness which sin had blotted out; and this mercy comes upon the human race through our Lord Jesus Christ. “For there is one God, and one Mediator between God and men, the Man Christ Jesus.”