The seventh book shows from various statements made to the Corinthians and to the Hebrews, and from the words of the Lord, that the word Lord is not expressive of essence, according to Eunomius' exposition, but of dignity. and after many notable remarks concerning the Spirit and the Lord, he shows that Eunomius, from his own words, is found to argue in favour of orthodoxy, though without intending it, and to be struck by his own shafts
Since, however, Eunomius asserts that the word “Lord” is used in reference to the essence and not to the dignity of the Only-begotten, and cites as a witness to this view the Apostle, when he says to the Corinthians, “Now the Lord is the Spirit,” it may perhaps be opportune that we should not pass over even this error on his part without correction. He asserts that the word “Lord” is significative of essence, and by way of proof of this assumption he brings up the passage above mentioned.
“The Lord,” it says, “is the Spirit.” But our friend who interprets Scripture at his own sweet will calls “Lordship” by the name of “essence,” and thinks to bring his statement to proof by means of the words quoted. Well, if it had been said by Paul, “Now the Lord is essence,” we too would have concurred in his argument. But seeing that the inspired writing on the one side says, “the Lord is the Spirit,” and Eunomius says on the other, “Lordship is essence,” I do not know where he finds support for his statement, unless he is prepared to say again that the word “Spirit” stands in Scripture for “essence.”
Let us consider, then, whether the Apostle anywhere, in his use of the term “Spirit,” employs that word to indicate “essence.” He says, “The Spirit itself bears witness with our Spirit,” and “no one knows the things of a man save the Spirit of man which is in him,” and “the letter kills, but the Spirit gives life,” and “if you through the Spirit do mortify the deeds of the body, you shall live,” and “if we live in the Spirit let us also walk in the Spirit.” Who indeed could count the utterances of the Apostle on this point?
And in them we nowhere find “essence” signified by this word. For he who says that “the Spirit itself bears witness with our spirit,” signifies nothing else than the Holy Spirit Which comes to be in the mind of the faithful; for in many other passages of his writings he gives the name of spirit to the mind, on the reception by which of the communion of the Spirit the recipients attain the dignity of adoption. Again, in the passage, “No one knows the things of a man save the spirit of man which is in him,” if “man” is used of the essence, and “spirit” likewise, it will follow from the phrase that the man is maintained to be of two essences.
Again, I know not how he who says that “the letter kills, but the Spirit gives life,” sets “essence” in opposition to “letter”; nor, again, how this writer imagines that when Paul says that we ought “through the Spirit” to destroy “the deeds of the body,” he is directing the signification of “spirit” to express “essence”; while as for “living in the Spirit,” and “walking in the Spirit,” this would be quite unintelligible if the sense of the word “Spirit” referred to “essence.” For in what else than in essence do all we who are alive partake of life?— thus when the Apostle is laying down advice for us on this matter that we should “live in essence,” it is as though he said “partake of life by means of yourselves, and not by means of others.”
If then it is not possible that this sense can be adopted in any passage, how can Eunomius here once more imitate the interpreters of dreams, and bid us to take “spirit” for “essence,” to the end that he may arrive in due syllogistic form at his conclusion that the word “Lord” is applied to the essence?— for if “spirit” is “essence” (he argues), and “the Lord is Spirit,” the “Lord” is clearly found to be “essence.” How incontestable is the force of this attempt! How can we evade or resolve this irrefragable necessity of demonstration?
The word “Lord,” he says, is spoken of the essence. How does he maintain it? Because the Apostle says, “The Lord is the Spirit.” Well, what has this to do with essence? He gives us the further instruction that “spirit” is put for “essence.” These are the arts of his demonstrative method! These are the results of his Aristotelian science! This is why, in your view, we are so much to be pitied, who are uninitiated in this wisdom! And you of course are to be deemed happy, who track out the truth by a method like this— that the Apostle's meaning was such that we are to suppose “the Spirit” was put by him for the Essence of the Only-begotten!
Source: Against Eunomius (New Advent)