Basil: Contra Eunomius 1.19

In order to keep our treatise from becoming excessively long by going through each of the blasphemies and trying to correct everything he said, we will omit those passages whose impiety is obvious and immediately manifest to those who read them. Instead, we will adduce those passages which need some argument for their refutation. After he established in manifold ways that the Father’s substance has no fellowship with the Son and demonstrated absurdity in every way (or so he thinks), he adds:

Now they would certainly not say the following: that while the substance is common to both, it is due to order and to superiorities based on time that the one is a first and the other a second. This is because the cause of the pre-eminence must be present in that which is pre-eminent, but neither time nor age nor order has been joined with the substance of God. For order is secondary to the orderer, but nothing that belongs to God has been ordered by another. Time is a certain kind of motion of the stars, but the stars came into being not only later than the substance of the unbegotten and all the intelligibles, but also later than the primary bodies. Do we not even need to speak about ages? For scripture clearly declares: Before the ages God exists (Ps. 54.20).

In the course of the treatise he has presupposed whatever he wanted and drawn what follows from his presuppositions. Then, diving headlong into absurd notions, he thinks that from this reasoning he has demonstrated the necessity of accepting his own doctrines. He says: “they would not say the following: that while the substance is common to both, it is due to order and superiorities based on time that the one is a first and the other a second.” So then, if he is speaking of the commonality of the substance, conceiving it to be a king of doling out and division of pre-existent matter into things that come from it, this understanding is unacceptable to us. God forbid! We declare that those who speak in this way (of indeed anyone really does) are no less impious that those who affirm the ‘unlike.’ But if someone takes the commonality of the substance to mean that one and the same formula of being is observed in both, such that if, hypothetically speaking, the Father is conceived of as light in his substrate, then the substance of the Only-Begotten is also confessed as light, and whatever one may assign to the Father as the formula of his being, the very same also applies to the Son. If someone takes the commonality of the substance in this way, we accept it and claim it as our doctrine. For this is how divinity is one. Clearly, their unity is conceived to be a matter of the formula of the substance. Hence while there is difference in number and in distinctive features that characterise each, their unity is observed in the formula of the divinity.