Book 6.21

"I should be sure," replies he, "that the sun and the moon wished to do us good, if they were able to refuse to do so; but they cannot help moving as they do. In short, let them stop and discontinue their work."

See now, in how many ways this argument may be refuted. One who cannot refuse to do a thing may nevertheless wish to do it; indeed there is no greater proof of a fixed desire to do anything, than not to be able to alter one's determination. A good man cannot leave undone what he does: for unless he does it he will not be a good man. Is a good man, then, not able to bestow a benefit, because he does what he ought to do, and is not able not to do what he ought to do? Besides this, it makes a great difference whether you say, "He is not able not to do this, because he is forced to do it," or "He is not able to wish not to do it;" for, if he could not help doing it, then I am not indebted for it to him, but to the person who forced him to do it; if he could not help wishing for it because he had nothing better to wish for, then it is he who forces himself to do it, and in this case the debt which as acting under compulsion he could not claim, is due to him as compelling himself.

"Let the sun and moon cease to wish to benefit us," says our adversary. I answer, "Remember what has been said. Who can be so crazy as to refuse the name of free-will to that which has no danger of ceasing to act, and of adopting the opposite course, since, on the contrary, he whose will is fixed for ever, must be thought to wish more earnestly than any one else. Surely if he, who may at any moment change his mind, can be said to wish, we must not deny the existence of will in a being whose nature does not admit of change of mind.