Nicene and Post-Nicene Fathers: Series I/Volume IV/Manichaean Controversy/On the Morals of the Manichaeans/Chapter 12
Chapter 12.—Manichæan Subterfuge.
25. For this gives rise to the question, which used to throw us into great perplexity even when we were your zealous disciples, nor could we find any answer,—what the race of darkness would have done to God, supposing He had refused to fight with it at the cost of such calamity to part of Himself. For if God would not have suffered any loss by remaining quiet, we thought it hard that we had been sent to endure so much. Again, if He would have suffered, His nature cannot have been incorruptible, as it behoves the nature of God to be. Sometimes the answer was, that it was not for the sake of escaping evil or avoiding injury, but that God in His natural goodness wished to bestow the blessing of order on a disturbed and disordered nature. This is not what we find in the Manichæan books: there it is constantly implied and constantly asserted that God guarded against an invasion of His enemies. But supposing this answer, which was given from want of a better, to represent the opinion of the Manichæans, is God, in their view, vindicated from the charge of cruelty or weakness? For this goodness of His to the hostile race proved most pernicious to His own subjects. Besides, if God’s nature could not be corrupted nor changed, neither could any destructive influence corrupt or change us; and the order to be bestowed on the race of strangers might have been bestowed without robbing us of it.
26. Since those times, however, another answer has appeared which I heard recently at Carthage. For one, whom I wish much to see brought out of this error, when reduced to this same dilemma, ventured to say that the kingdom had its own limits, which might be invaded by a hostile race, though God Himself could not be injured. But this is a reply which your founder would never consent to give; for he would be likely to see that such an opinion would lead to a still speedier demolition of his heresy. And in fact any one of average intellect, who hears that in this nature part is subject to injury and part not, will at once perceive that this makes not two but three natures,—one violable, a second inviolable, and a third violating.