The Five Books Against Marcion by Tertullian
Chapter IV.--Defence of the Divine Unity Against Objection No Analogy Between Human Powers and God's Sovereignty. The Objection Otherwise Untenable, for Why Stop at Two Gods?
But some one may contend that two great Supremes may exist, distinct and separate in their own departments; and may even adduce, as an example, the kingdoms of the world, which, though they are so many in number, are yet supreme in their several regions. Such a man will suppose that human circumstances are always comparable with divine ones. Now, if this mode of reasoning be at all tolerable, what is to prevent our introducing, I will not say a third god or a fourth, but as many as there are kings of the earth? Now it is God that is in question, whose main property it is to admit of no comparison with Himself. Nature itself, therefore, if not an Isaiah, or rather God speaking by Isaiah, will deprecatingly ask, |To whom will ye liken me?| Human circumstances may perhaps be compared with divine ones, but they may not be with God. God is one thing, and what belongs to God is another thing. Once more: you who apply the example of a king, as a great supreme, take care that you can use it properly. For although a king is supreme on his throne next to God, he is still inferior to God; and when he is compared with God, he will be dislodged from that great supremacy which is transferred to God. Now, this being the case, how will you employ in a comparison with God an object as your example, which fails in all the purposes which belong to a comparison? Why, when supreme power among kings cannot evidently be multifarious, but only unique and singular, is an exception made in the case of Him (of all others) who is King of kings, and (from the exceeding greatness of His power, and the subjection of all other ranks to Him) the very summit, as it were, of dominion? But even in the case of rulers of that other form of government, where they one by one preside in a union of authority, if with their petty prerogatives of royalty, so to say, they be brought on all points into such a comparison with one another as shall make it clear which of them is superior in the essential features and powers of royalty, it must needs follow that the supreme majesty will redound to one alone, -- all the others being gradually, by the issue of the comparison, removed and excluded from the supreme authority. Thus, although, when spread out in several hands, supreme authority seems to be multifarious, yet in its own powers, nature, and condition, it is unique. It follows, then, that if two gods are compared, as two kings and two supreme authorities, the concentration of authority must necessarily, according to the meaning of the comparison, be conceded to one of the two; because it is clear from his own superiority that he is the supreme, his rival being now vanquished, and proved to be not the greater, however great. Now, from this failure of his rival, the other is unique in power, possessing a certain solitude, as it were, in his singular pre-eminence. The inevitable conclusion at which we arrive, then, on this point is this: either we must deny that God is the great Supreme, which no wise man will allow himself to do; or say that God has no one else with whom to share His power.