Evodius (asking Augustine): “Since God foreknew that man would sin, that which God foreknew must come to pass. How then is the will free when there is apparently this unavoidable necessity?”
Augustine: “God by his foreknowledge does not use compulsion in the case of future events . . . God has foreknowledge of all his own actions, but is not the agent of all that he foreknows . . . he has no responsibility for the future actions of men though he knows them beforehand.”
Augustine explains that although God gives free will the use of it is up to the human agent: “If you see a man without feet you will admit that, from the point of view of the wholeness of his body, a very great good is wanting. And yet you would not deny that a man makes a bad use of his feet who uses them to hurt another or to dishonour himself.”
Nevertheless, apart from God’s mercy, no act of the will will make any difference in the eternal destiny of a human soul: “For the effectiveness of God’s mercy cannot be in the power of man to frustrate, if he will have none of it. If God wills to have mercy on men, he can call them in a way that is suited to them, so that they will be moved to understand and to follow . . . it is false to say that “it is not of God who hath mercy but of man who willeth and runneth,” because God has mercy on no man in vain. He calls the man on whom he has mercy in the way he knows will suit him, so that he will not refuse the call.”
Quotes from: “On Free Will,” trans. J.H.S. Burleigh, in The Library of Christian Classics, ed. John Baillie, John T. McNeill and Henry P. Van Dusen, Augustine: Earlier Writings, (Philadelphia: Westminster) and “The Spirit and the Letter” and “The Simplican,” introduction by John Burnaby, trans. John Burnaby, in The Library of Christian Classics, ed. John Baillic, John T. McNeill and Henry P. Van Dusen, Augustine: Later Works, (Philadelphia: Westminster).