In proof of the Unity in Trinity the passage of Isaiah which has been cited is considered, and it is shown that there is no difference as to its sense amongst those who expound it of the Father, or of the Son, or of the Spirit. If He Who was crucified was Lord of glory, so, too, is the Holy Spirit equal in all things to the Father and the Son, and the Arians will never be able to diminish His glory.
165. It is now possible to recognize the oneness of the majesty and rule in the Father, the Son, and the Holy Spirit. For many say that it was God the Father Who was seen at that time by Isaiah. Paul says it was the Spirit, and Luke supports him. John the Evangelist refers it to the Son. For thus has he written of the Son: |These things spake Jesus, and departed and hid Himself from them. But though He had done so great signs before them, they did not believe on Him, that the word of Isaiah might be fulfilled which he spake, Lord, who hath believed our report, and to whom hath the Arm of the Lord been revealed? Therefore, they could not believe, because Isaiah said again, He hath blinded their eyes and hardened their heart, that they might not see with their eyes and understand with their heart and be converted, and I should heal them. These things said Isaiah when he saw His glory, and spake of Him.|
166. John says that Isaiah spoke these words, and revealed most clearly that the glory of the Son appeared to him. Paul, however, relates that the Spirit said these things. Whence, then, is this difference?
167. There is, indeed, a difference of words, not of meaning. For though they said different things, neither was in error, for both the Father is seen in the Son, Who said, |He that seeth Me seeth the Father also,| and the Son is seen in the Spirit; for as |no man says Lord Jesus, except in the Holy Spirit,| so Christ is seen not by the eye of flesh, but by the grace of the Spirit. Whence, too, the Scripture says: |Rise, thou that sleepest, and arise from the dead, and Christ shall shine upon thee.| And Paul, when he had lost his eyesight, how did he see Christ except in the Spirit? Wherefore the Lord says: |For to this end I have appeared unto thee, to appoint thee a minister and a witness of the things wherein thou hast seen Me, and of the things wherein thou shalt see Me.| For the prophets also received the Spirit and saw Christ.
168. One, then, is the vision, one the right to command, one the glory. Do we deny that the Holy Spirit is also the Lord of glory when the Lord of glory was crucified who was born from the Holy Spirit of the Virgin Mary? For Christ is not one of two, but is one, and was born as Son of God of the Father before the world; and in the world born as man by taking flesh.
169. And why should I say that, as the Father and the Son, so, too, the Spirit is free from stain and Almighty, for Solomon called Him in Greek pantodunamon, panepischopon , because He is Almighty and beholds all things, as we showed above to be, is read in the Book of Wisdom. Therefore the Spirit enjoys honour and glory.
170. Consider now lest perchance something may not beseem Him, or if this displease thee, O Arian, drag Him down from His fellowship with the Father and the Son. But if thou choose to drag Him down thou wilt see the heavens reversed above thee, for all their strength is from the Spirit. If thou choose to drag Him down, thou must first lay hands on God, for the Spirit is God. But how wilt thou drag Him down, Who searcheth the deep things of God?