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 heart Acts iv. 32: in this and the following passages unum is read., and again, He that planteth and He that watereth are one 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 Us 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.