The _Defensio Fidei Nicenæ_ (1685) was written not to establish, by proofs from Scripture, the doctrine of Christ’s Divinity, but to show that the opinions of the ante-Nicene Fathers upon the subject, were in harmony with those expressed in the Creed of the first Œcumenical Council. This purpose Bull formed, in consequence of an attack upon those Fathers, by the learned Jesuit Petavius, and the use made of that attack, for ends opposed to his, by Arians and Socinians. The most perfect success on the part of the Anglican advocate would not, in the estimation of Divines of the Puritan school, be conclusive evidence of our Lord’s Deity, nor would his failure shake their faith; but the importance which he attached to the question, appears from the immense labour which he devoted to it. To him, as an Anglo-Catholic, the inquiry into what the early Church believed and taught appeared one of vital interest; and into his chosen task he threw the treasures of a vast erudition, and, if not powers of the highest order, certainly a decisive will and an extraordinarily active and patient inquisitiveness. Parts of his argument, it must be confessed, seem unsatisfactory. For he deals with his patristic authorities, as we do with the Holy Scriptures. Whilst we reasonably assume that the latter are always consistent, and therefore endeavour to harmonize _apparent_ discrepancies, he assumes the same with regard to the writings of the Fathers. Hence he attempts to reconcile contradictory passages in the same author, and also contradictory passages in different authors. Moreover, upon a presumption of the perfect unity of patristic opinions, and of a thoroughly logical apprehension of subjects on the part of the Fathers, he sometimes educes proofs not from what they plainly say in so many words, but from what their language may be made to imply, when analyzed and manipulated with the utmost sagacity and skill. Loyal men standing at the bar have been unjustly arraigned for constructive treason. In controversy men of the soundest opinion have been unrighteously charged with constructive heresy. On the other hand, Bull’s method of criticism serves sometimes to vindicate opinions open to suspicion, and so to throw around doubtful points the halo of a constructive orthodoxy.[400] [Sidenote: ANGLICANS.--HEYLYN.]