The Enchiridion by St. Augustine
Chapter 99.--As God's Mercy is Free, So His Judgments are Just, and Cannot Be Gainsaid.
Now after commending the mercy of God, saying, |So it is not of him that willeth, nor of him that runneth, but of God that showeth mercy,| that he might commend His justice also (for the man who does not obtain mercy finds, not iniquity, but justice, there being no iniquity with God), he immediately adds: |For the scripture saith unto Pharoah, Even for this same purpose have I raised thee up, that I might show my power in thee, and that my name might be declared throughout all the earth.| And then he draws a conclusion that applies to both, that is, both to His mercy and His justice: |Therefore hath He mercy on whom He will have mercy, and whom He will He hardeneth.| |He hath mercy| of His great goodness, |He hardeneth| without any injustice; so that neither can he that is pardoned glory in any merit of his own, nor he that is condemned complain of anything but his own demerit. For it is grace alone that separates the redeemed from the lost, all having been involved in one common perdition through their common origin. Now if any one, on hearing this, should say, |Why doth He yet find fault? for who hath resisted His will?| as if a man ought not to be blamed for being bad, because God hath mercy on whom He will have mercy, and whom He will He hardeneth, God forbid that we should be ashamed to answer as we see the apostle answered: |Nay, but, O man, who art thou that repliest against God? Shall the thing formed say to Him that formed it, Why hast Thou made me thus? Hath not the potter power over the clay, of the same lump to make one vessel unto honor, and another unto dishonor?| Now some foolish people, think that in this place the apostle had no answer to give; and for want of a reason to render, rebuked the presumption of his interrogator. But there is great weight in this saying: |Nay, but, O man, who art thou?| and in such a matter as this it suggests to a man in a single word the limits of his capacity, and at the same time does in reality convey an important reason. For if a man does not understand these matters, who is he that he should reply against God? And if he does understand them, he finds no further room for reply. For then he perceives that the whole human race was condemned in its rebellious head by a divine judgment so just, that if not a single member of the race had been redeemed, no one could justly have questioned the justice of God; and that it was right that those who are redeemed should be redeemed in such a way as to show, by the greater number who are unredeemed and left in their just condemnation, what the whole race deserved, and whither the deserved judgment of God would lead even the redeemed, did not His undeserved mercy interpose, so that every mouth might be stopped of those who wish to glory in their own merits, and that he that glorieth might glory in the Lord.