It may be asked: How can he be forestalled by any aid of grace, who puts obstacles in the way of grace, by being already in sin and going on to fresh sin? The answer is, that grace and good will are strong enough to break down any obstacle. But in this case a great grace is needed, e.g., a thorough fright. And that is the rationale of the sermons on hell that are preached in Lenten missions. They are as heavy siege artillery to breach the castle of the strong man armed (Luke xi, 21).
Of God and His Creatures: 3.161