The variation of the manuscripts was not the only obstacle to biblical infallibility. To say nothing of differences of interpretation there was the question of the canon. Either the decision of the 'catholic' church must be accepted as infallible, or scholarship must undertake a 'criticism of the canon' to defend the current list of "inspired" books. A 'higher' criticism became necessary if only to vindicate the church's choice on historical grounds. Roman Catholics like Simon, whose _Critical History_ of the Biblical books appeared in 1689-1695, could reopen the question with impunity. Those who based their authority on the infallibility of Scripture alone could not meet the challenge otherwise than as Michælis did in his _Introduction to the Divine Writings of the New Testament_ (1750-1780). Michælis undertook a historical inquiry into the circumstances of origin of each of the canonical books, with the object of proving each to be in reality what tradition declared. The twenty-seven commonly accepted were supposed to have been either written by apostles, or at least so super-intended and guaranteed by them, as to cover all with the ægis of an infallibility not conceded to the post-apostolic age. Scholarship in the harness of apologetics again found its task impracticable. Michælis himself confessed it "difficult" to prove authenticity in cases like that of the Epistle of Jude. Conceive the task as the scientific vindication of a verdict rendered centuries before on unknown grounds, but now deprived of official authority, and it becomes inevitably hopeless. Can it be expected that doctors will not disagree on the authenticity or pseudonymity of 2nd Peter, who always have disagreed on this and similar questions, and have just admitted failure to agree in the matter of text? For half a century criticism seemed lost in the slough of mere controversy over the (assumed) infallible text, and the (assumed) infallible canon. Apologists fought merely on the defensive, endeavouring to prove that men whose fallibility was admitted had nevertheless pronounced an infallible verdict on the most difficult subjects of literary and historical inquiry. Critics had an easy task in showing that the church's theory of inspiration and canonicity was incorrect; but made no progress toward a constructive explanation of the religious, or even the historical, significance of the literature. Real progress was made only when criticism left off the attempt either to establish or disestablish a 'received' text, or an 'authorized' canon, and became simply an instrument in the hand of the historian, as he seeks to trace to their origins the ideas the church enshrined in her literature because she found them effective in her growth.