It’s unfitting for God to fail to complete His purpose in the world, Anselm says. But his argument seems to imply that God is constrained to save. If this is true, Boso wonders, do we owe Him gratitude? After all, as Anselm himself admits, “when someone acts beneficently against his will due to the unavoidable force of circumstances to which he is subject, he is owed either no gratitude or less.”
But that’s not God’s situation. He is not coerced by outside circumstances. He freely subjects Himself by making a promise. This obligates Him to keep His promise, but because He volunteered to do the good, his action is not “an act of necessity but an act of grace.” Keeping a voluntary promise or vow is not a necessity at all, but rather, since the original commitment is free, so is the fulfillment of the commitment.
Thus: “Despite the fact that it is not fitting for God to fail to bring to completion a good beginning, we ought all the more to attribute it entirely to his grace if he completes the act of beneficence towards mankind which he has begun, seeing that he has begun it for our sake, not for his own, being himself in need of nothing.” Thus too we own Him gratitude.