God Alone Perfectly Good
42 What harm, you ask, would follow if those things too were perfectly good? Still, should any one, who admits and believes the perfect goodness of God the Father, inquire what source we should reverently assign to any other perfectly good thing, supposing it to exist, our only correct reply would be, that it is of God the Father, who is perfectly good. And we must bear in mind that what is of Him is born of Him, and not made by Him out of nothing, and that it is therefore perfectly, that is, incorruptibly, good like God Himself. So we see that it is unreasonable to require that things made out of nothing should be as perfectly good as He who was begotten of God Himself, and who is one as God is one, otherwise God would have begotten something unlike Himself. Hence it shows ignorance and impiety to seek for brethren for this only-begotten Son through whom all good things were made by the Father out of nothing, except in this, that He condescended to appear as man. Accordingly in Scripture He is called both only-begotten and first-begotten; only-begotten of the Father, and first-begotten from the dead. "And we beheld," says John, "His glory, the glory as of the only-begotten of the Father, full of grace and truth." And Paul says, "that He might be the first-born among many brethren."
43. But should we say, These things made out of nothing are not good things, but only God's nature is good, we shall be unjust to good things of great value. And there is impiety in calling it a defect in anything not to be what God is, and in denying a thing to be good because it is inferior to God. Pray submit then, you nature of the rational soul, to be somewhat less than God, but only so far less, that after Him nothing else is above you. Submit, I say, and yield to Him, lest He drive you still lower into depths where the punishment inflicted will continually detract more and more from the good which you have. Thou exaltest yourself against God, if you are indignant at His preceding you; and you are very contumacious in your thoughts of Him, if you do not rejoice unspeakably in the possession of this good, that He alone is above you. This being settled as certain, you are not to say, God should have made me the only nature: there should be no good thing after me. It could not be that the next good thing to God should be the last. And in this is seen most clearly how great dignity God conferred on you, that He who in the order of nature alone rules over you, made other good things for you to rule over. Nor be surprised that they are not now in all respects subject to you, and that sometimes they pain you; for your Lord has greater authority over the things subject to you than you have, as a master over the servants of his servants. What wonder, then, if, when you sin, that is, disobeyest your Lord, the things you before ruled over are made instrumental in your punishment? For what is so just, or what is more just than God? For this befell human nature in Adam, of whom this is not the place to speak. Suffice it to say, the righteous Ruler acts in character both in just rewards and in just punishments, in the happiness of those who live rightly, and in the penalty inflicted on sinners. Nor yet are you left without mercy, since by an appointed distribution of things and times you are called to return. Thus the righteous control of the supreme Creator extends even to earthly good things, which are corrupted and restored, that you might have consolations mingled with punishments; that you might both praise God when delighted by the order of good things, and might take refuge in Him when tried by experience of evils. So, as far as earthly things are subject to you, they teach you that you are their ruler; as far as they distress you, they teach you to be subject to your Lord.
Source: Against the Epistle of Manichaeus Called Fundamental (New Advent)