Book VI. Hilary begins by lamenting the wide extension of Arianism; his love for souls leads him to combat the heresy, whose insidiousness makes it the more dangerous (§§ 1–4). He repeats in §§ 5, 6 the same Arian creed which he had given in Book IV. The heretics here gain the appearance of orthodoxy by condemning errors inconsistent with their own; and this condemnation is designed to cast upon the Catholic faith the suspicion of complicity in such errors. Hence he must postpone his appeal to the New Testament till he has examined them (§§ 7, 8). Accordingly in §§ 9–12 he explains successively the doctrines of Valentinus, Manichæus, Sabellius and Hieracas, and shews that the Church rejects them all, as she does (§ 13) the doctrine which the Arians in their creed have falsely assigned to her. Their object is to deny that the Son is coeternal with the Father and of one substance with Him (§§ 14, 15); but this denial is clean contrary to Scripture, which it is blasphemy to oppose (§§ 16, 17). The Arians would make a creature of Christ (§ 18), to Whom, in §§ 19–21, Hilary turns with an impassioned declaration of certainty that He is very God. He then resumes the argument, and proves that Christ is Son by birth, not by adoption, from the words both of Father and of Son as recorded in the Gospel (§§ 22–25). This is confirmed (§§ 26, 27) by the Gospel account of His acts, which are otherwise inexplicable. The argument is clenched by a discussion of St. John vii. 28, 29, and viii. 42 (§§ 28–31). The true Sonship of Christ is further proved by the faith of the Apostles, whose certainty increased with their knowledge (§§ 31–35), and especially by that of St. Peter (§§ 36–38), of St. John (§§ 39–43), and of St. Paul (§§ 44, 45). To reject such a weight of testimony is to prefer Antichrist to Christ (§ 46). And, moreover, we have the witness of those for whom He wrought miracles, of devils, of the Jews, the Apostles in peril on the sea, of the centurion by the Cross, that Christ is truly the Son of God (§§ 47–52).