Basil Contra Eunomius 1.23

As far as I am concerned, I do not think that even you are so insane that you would definitely affirm that the Son is anything other than incorporeal and without form and without figure and everything else you would affirm in the case of the Father. How, then, is it not in line with piety to compare one without form to one without form? The one without size to the one without it? The one without composition to the one without composition? But Eunomius considers likeness to be a question of form, and equality a question of mass; as for size, whatever he thinks it is besides mass he will have to explain more properly. “For this reason,” he says, “He is neither equal nor like, since he is both without quantity and without form.” But for my part, I consider likeness to comprise in this very thing, since just as the Father is entirely free from composition, so too is the Son altogether simple and without composition. In addition, one does not consider likeness according to identity of form. On the other hand, all that remains for the nature that is without form and without shape is that it has likeness in the substance itself, and this case equality is not a question of comparing masses, but rather the identity of power: “For Christ is the power of God” [1Cor 1.24]. It is clear that all the Father’s power is contained in Him. Therefore, whatsoever he should “see the Father doing, these same the Son does likewise” [John 5.19].

But he says: “Neither likeness nor comparison, nor fellowship in substance allows for any pre-eminence or difference, but rather they clearly bring about equality.” How does this allow for no difference? Not even the difference exists between causes and their effects? Then he adds: “But who is so stupid or so defiant of piety as to say that the Son is equal to the Father?” So, then, let us state a response to him using the words of the prophet: “You have acquired the face of a whore, you have no shame before anyone” [Jer. 3.3]. The ill repute of these women tarnishes those who have lived honourably, and Eunomius disparages them as stupid and defiant of piety those who desire to exalt the glory of the Only-Begotten, showing harshness toward them for the same reasons that also provoked the Jews when they said, “He makes Himself equal to God [John 5.18]