Against Celsus 3.70

Then he raises as an objection, as if said by us, “God will be able to do all things,” not seeing even this, how it is said, what “all things” are included in it, and how he is able. It is not necessary to speak about these matters now, for he himself did not take a stand against it, though he could have done so plausibly; perhaps because he did not grasp the plausible argument that could be made against it, or because he grasped it but also saw the answer to it. In our view God can do all things which he can do without ceasing to be God, good, and wise. But Celsus, as one who has not understood in what sense God is said to be able to do all things, says that “he will not want anything unjust,” granting that he can do even what is unjust, but does not will it. We say that just as what is by nature sweetening, because it is sweet, cannot make bitter contrary to its own sole cause, and what is by nature illuminating, because it is light, cannot darken, so neither can God do injustice; for the power to do injustice is contrary to his divinity and to all the power that belongs to it. And if any being can do injustice because it is also by nature inclined to do injustice, it can do injustice because it does not have in its nature the utter inability to do injustice.