Anti-pelagian Writings by St. Augustine
Chapter 38.--What is the Nature of the Gift of Perseverance that is Now Given to the Saints.
And thus God willed that His saints should not -- even concerning perseverance in goodness itself -- glory in their own strength, but in Himself, who not only gives them aid such as He gave to the first man, without which they cannot persevere if they will, but causes in them also the will; that since they will not persevere unless they both can and will, both the capability and the will to persevere should be bestowed on them by the liberality of divine grace. Because by the Holy Spirit their will is so much enkindled that they therefore can, because they so will; and they therefore so will because God works in them to will. For if in so much weakness of this life (in which weakness, however, for the sake of checking pride, strength behoved to be perfected) their own will should be left to themselves, that they might, if they willed, continue in the help of God, without which they could not persevere, and God should not work in them to will, in the midst of so many and so great weaknesses their will itself would give way, and they would not be able to persevere, for the reason that failing from infirmity they would not will, or in the weakness of will they would not so will that they would be able. Therefore aid is brought to the infirmity of human will, so that it might be unchangeably and invincibly influenced by divine grace; and thus, although weak, it still might not fail, nor be overcome by any adversity. Thus it happens that man's will, weak and incapable, in good as yet small, may persevere by God's strength; while the will of the first man, strong and healthful, having the power of free choice, did not persevere in a greater good; because although God's help was not wanting, without which it could not persevere if it would, yet it was not such a help as that by which God would work in man to will. Certainly to the strongest He yielded and permitted to do what He willed; to those that were weak He has reserved that by His own gift they should most invincibly will what is good, and most invincibly refuse to forsake this. Therefore when Christ says, |I have prayed for thee that thy faith fail not,| we may understand that it was said to him who is built upon the rock. And thus the man of God, not only because he has obtained mercy to be faithful, but also because faith itself does not fail, if he glories, must glory in the Lord.