Ante-Nicene Fathers, Vol III:
Tertullian: Part II: The Dual Principle Falls to the Ground; Plurality of Gods, of Whatever Number, More Consistent. Absurdity and Injury to Piety Resulting from Marcion's Duality.

Chapter V.—The Dual Principle Falls to the Ground; Plurality of Gods, of Whatever Number, More Consistent. Absurdity and Injury to Piety Resulting from Marcion’s Duality.

But on what principle did Marcion confine his supreme powers to two? I would first ask, If there be two, why not more? Because if number be compatible with the substance of Deity, the richer you make it in number the better. Valentinus was more consistent and more liberal; for he, having once imagined two deities, Bythos and Sige, 2381 poured forth a swarm of divine essences, a brood of no less than thirty Æons, like the sow of Æneas. 2382 Now, whatever principle refuses to admit several supreme beings, the same must reject even two, for there is plurality in the very lowest number after one.  After unity, number commences. So, again, the same principle which could admit two could admit more.  After two, multitude begins, now that one is exceeded. In short, we feel that reason herself expressly 2383 forbids the belief in more gods than one, because the self-same rule lays down one God and not two, which declares that God must be a Being to which, as the great Supreme, nothing is equal; and that Being to which nothing is equal must, moreover, be unique. But further, what can be the use or advantage in supposing two supreme beings, two co-ordinate 2384 powers? What numerical difference could there be when two equals differ not from one?  For that thing which is the same in two is one. Even if there were several equals, all would be just as much one, because, as equals, they would not differ one from another. So, if of two beings neither differs from the other, since both of them are on the supposition 2385 supreme, both being gods, neither of them is more excellent than the other; and so, having no pre-eminence, their numerical distinction 2386 has no reason in it. Number, moreover, in the Deity ought to be consistent with the highest reason, or else His worship would be brought into doubt. For consider 2387 now, if, when I saw two Gods before me (who, being both Supreme Beings, were equal to each other), I were to worship them both, what should I be doing? I should be much afraid that the abundance of my homage would be deemed superstition rather than piety. Because, as both of them are so equal and are both included in either of the p. 275 two, I might serve them both acceptably in only one; and by this very means I should attest their equality and unity, provided that I worshipped them mutually the one in the other, because in the one both are present to me. If I were to worship one of the two, I should be equally conscious of seeming to pour contempt on the uselessness of a numerical distinction, which was superfluous, because it indicated no difference; in other words, I should think it the safer course to worship neither of these two Gods than one of them with some scruple of conscience, or both of them to none effect.

Footnotes

Depth and silence.

See Virgil, Æneid, viii. 43, etc.

Ipso termino.

Paria.

Jam.

Numeri sui.

Ecce.