On the Morals of the Manichaeans

⁵ Let us then inquire more carefully, and, if possible, more plainly. I ask you again, What is evil? If you say it is that which is hurtful, here, too, you will not answer amiss. But consider, I pray you; be on your guard, I beg of you; be so good as to lay aside party spirit, and make the inquiry for the sake of finding the truth, not of getting the better of it. Whatever is hurtful takes away some good from that to which it is hurtful; for without the loss of good there can be no hurt.

What, I appeal to you, can be plainer than this? What more intelligible? What else is required for complete demonstration to one of average understanding, if he is not perverse? But, if this is granted, the consequence seems plain. In that race which you take for the chief evil, nothing can be liable to be hurt, since there is no good in it. But if, as you assert, there are two natures—the kingdom of light and the kingdom of darkness; since you make the kingdom of light to be God, attributing to it an uncompounded nature, so that it has no part inferior to another, you must grant, however decidedly in opposition to yourselves, you must grant, nevertheless, that this nature, which you not only do not deny to be the chief good, but spend all your strength in trying to show that it is so, is immutable, incorruptible, impenetrable, inviolable, for otherwise it would not be the chief good; for the chief good is that than which there is nothing better, and for such a nature to be hurt is impossible.

Again, if, as has been shown, to hurt is to deprive of good, there can be no hurt to the kingdom of darkness, for there is no good in it. And as the kingdom of light cannot be hurt, as it is inviolable, what can the evil you speak of be hurtful to?