Let the inquirer still go on, and say, “Why is it that to some who have in good faith worshipped Him He has not given to persevere to the end?” Why except because he does not speak falsely who says, “They went out from us, but they were not of us; for if they had been of us, doubtless they would have continued with us.” Are there, then, two natures of men? By no means. If there were two natures there would not be any grace, for there would be given a gratuitous deliverance to none if it were paid as a debt to nature. But it seems to men that all who appear good believers ought to receive perseverance to the end. But God has judged it to be better to mingle some who would not persevere with a certain number of His saints, so that those for whom security from temptation in this life is not desirable may not be secure. For that which the apostle says, checks many from mischievous elation: “Wherefore let him who seems to stand take heed lest he fall.” But he who falls, falls by his own will, and he who stands, stands by God’s will. “For God is able to make him stand;” therefore he is not able to make himself stand, but God. Nevertheless, it is good not to be high-minded, but to fear. Moreover, it is in his own thought that every one either falls or stands. Now, as the apostle says, and as I have mentioned in my former treatise, “We are not sufficient to think anything of ourselves, but our sufficiency is of God.” Following whom also the blessed Ambrose ventures to say, “For our heart is not in our own power, nor are our thoughts.” And this everybody who is humbly and truly pious feels to be most true.
Reproduced in full. Translation: Nicene and Post-Nicene Fathers, series 1, vol. 5 (Schaff, 1887), public domain (Public domain).