2. We call to mind that in the preceding books the reader has been urged to study the whole of that blasphemous manifesto The Epistola Arii ad Alexandrum; see Books iv. 12, vi. 5., and mark how it is animated throughout by the one aim of propagating the belief that our Lord Jesus Christ is neither God, nor Son of God. Its authors argue that He is permitted to use the names of God and of Son by virtue of a certain adoption, though neither Godhead nor Sonship be His by nature. They use the fact, true in itself, that God is immutable and incorporeal, as an argument against the birth of the Son from Him. They value the truth, that God the Father is One, only as a weapon against our faith in the Godhead of Christ; pleading that an incorporeal nature cannot be rationally conceived as generating another, and that our faith in One God is inconsistent with the confession of God from God. But our earlier books have already refuted and foiled this argument of theirs by an appeal to the Law and the Prophets. Our defence has followed, step by step, the course of their attack. We have set forth God from God, and at the same time confessed One true God; shewing that this presentation of the faith neither falls short of the truth by ascribing singleness of Person to the One true God, nor adds to the faith by asserting the existence of a second Deity. For we confess neither an isolated God, nor yet two Gods. Thus, neither denying that God is One nor maintaining that He is alone, we hold the straight road of truth. Each Divine Person is in the Unity, yet no Person is the One God. Next, our purpose being to demonstrate the irrefragable truth of this mystery by the evidence of the Evangelists and Apostles, our first duty has been to make our readers acquainted with the nature, truly subsisting and truly born, of the Son of God; to demonstrate that He has no origin external to God, and was not created out of nothing, but is the Son, born from God. This is a truth which the evidence adduced in the last book has placed beyond all doubt. The assertion that He bears the name of Son by virtue of adoption has been put to silence, and He stands forth as a true Son by a true birth. Our present task is to prove from the Gospels that, because He is true Son, He is true God also. For unless He be true Son He cannot be true God, nor true God unless He be true Son.