28. While its two predecessors have been devoted to the confirmation of the faith in Christ as Son of God and true God, the eighth book is taken up with the proof of the unity of God, shewing that this unity is consistent with the birth of the Son, and that the birth involves no duality in the Godhead. First it exposes the sophistry with which these heretics have attempted to avoid, though they could not deny, the confession of the real existence of God, Father and Son; it demolishes their helpless and absurd plea that in such passages as, And the multitude of them that believed were one soul and heart14    Acts iv. 32: in this and the following passages unum is read., and again, He that planteth and He that watereth are one15    1 Cor. iii. 8., and Neither for these only do I pray, but for them also that shall believe on Me through their word, that they may all be one, even as Thou, Father, art in Me, and I in Thee, that they also may be in Us16    St. John xvii. 20, 21., a unity of will and mind, not of Divinity, is expressed. From a consideration of the true sense of these texts we shew that they involve the reality of the Divine birth; and then, displaying the whole series of our Lord’s self-revelations, we exhibit, in the language of Apostles and in the very words of the Holy Spirit, the whole and perfect mystery of the glory of God as Father and as Only-begotten Son. Because there is a Father we know that there is a Son; in that Son the Father is manifested to us, and hence our certainty that He is born the Only-begotten and that He is very God.

28. Octavus liber.---Octavus jam vero liber, duobus superioribus 18 libris de Dei filio et Deo vero multum ad credentium fidem proficientibus, totus in unius Dei demonstratione detentus est; non auferens filio Dei nativitatem, sed neque per eam duum deorum divinitatem introducens. Ac primum quibus modis haeretici veritatem Dei patris et Dei filii, quia negare non possent, tamen eludere niterentur, edocuit; dissolvens ineptas eorum et ridiculas occasiones, quibus per id quod dictum est: Multitudinis autem credentium erat anima et cor unum (Act. IV, 32); et rursum: Qui plantat autem, et qui rigat, unum sunt (I Cor. III, 8); et iterum: Non pro his autem tantum rogo, sed et pro iis qui credituri sunt per verbum eorum in me: ut omnes unum sint, 0042C sicut tu, Pater, in me, et ego in te, ut et ipsi sint in nobis (Joan. XVII, 20, 21): voluntatis potius et unanimitatis quam divinitatis asserunt veritatem. Sed nos haec ipsa suis virtutibus pertractantes (hoc est, secundum vim verborum), fidem in se divinae nativitatis continere ostendimus: et omnes dictorum dominicorum professiones revolventes, totum atque perfectum, ex apostolicis praeconiis ac sancti Spiritus (Vocis sancti Spiritus, quae hic vis sit, videsis lib. VIII, n. 23) proprietatibus, et paternae et unigenitae majestatis sacramentum docuimus: cum et in Patre Filius intellectus, et Pater in Filio cognitus, unigeniti Dei nativitatem, et perfecti in eo Dei ostenderent veritatem.