Augustine of Hippo, On the Gift of Perseverance Chapter 21: Instances of the Unsearchable Judgments of God

Therefore, of two infants, equally bound by original sin, why the one is taken and the other left; and of two wicked men of already mature years, why this one should be so called as to follow Him that calleth, while that one is either not called at all, or is not called in such a manner,—the judgments of God are unsearchable. But of two pious men, why to the one should be given perseverance unto the end, and to the other it should not be given, God’s judgments are even more unsearchable. Yet to believers it ought to be a most certain fact that the former is of the predestinated, the latter is not. “For if they had been of us,” says one of the predestinated, who had drunk this secret from the breast of the Lord, “certainly they would have continued with us.” What, I ask, is the meaning of, “They were not of us; for if they had been of us, they would certainly have continued with us”? Were not both created by God—both born of Adam—both made from the earth, and given from Him who said, “I have created all breath,” souls of one and the same nature? Lastly, had not both been called, and followed Him that called them? and had not both become, from wicked men, justified men, and both been renewed by the laver of regeneration? But if he were to hear this who beyond all doubt knew what he was saying, he might answer and say: These things are true. In respect of all these things, they were of us. Nevertheless, in respect of a certain other distinction, they were not of us, for if they had been of us, they certainly would have continued with us. What then is this distinction? God’s books lie open, let us not turn away our view; the divine Scripture cries aloud, let us give it a hearing. They were not of them, because they had not been “called according to the purpose;” they had not been chosen in Christ before the foundation of the world; they had not gained a lot in Him; they had not been predestinated according to His purpose who worketh all things. For if they had been this, they would have been of them, and without doubt they would have continued with them.