Nicene and Post-Nicene Fathers: Series I/Volume V/On the Grace of Christ, and on Original Sin/On the Grace of Christ/Chapter 13

Chapter 13 [XII.]—Grace Causes Us to Do.

To him, therefore, who is reluctant to endure the troublesome process, whereby this vaunting disposition is restrained, before he attains to the ultimate and highest perfection of charity, it is most properly said, “My grace is sufficient for thee; for my strength is made perfect in weakness,” —in weakness, that is, not of the flesh only, as this man supposes, but both of the flesh and of the mind; because the mind, too, was, in comparison of that last stage of complete perfection, weak, and to it also was assigned, in order to check its elation, that messenger of Satan, the thorn in the flesh; although it was very strong, in contrast with the carnal or animal faculties, which as yet understand not the things of the Spirit of God. Inasmuch, then, as strength is made perfect in weakness, whoever does not own himself to be weak, is not in the way to be perfected. This grace, however, by which strength is perfected in weakness, conducts all who are predestinated and called according to the divine purpose to the state of the highest perfection and glory. By such grace it is effected, not only that we discover what ought to be done, but also that we do what we have discovered,—not only that we believe what ought to be loved, but also that we love what we have believed.