We come to what may be the hottest current debate among scholars concerning the formation of the Christian canon: the role of heretics. For scholars such as Adolph von Harnack and Hans von Campenhausen, the Marcionite heresy all but forced the formation of the New Testament scriptures. Indeed, Campenhausen went so far as to call Marcion the “creator of the Christian holy Scripture.” Bruce Metzger argues that the formative heretical forces were threefold: Gnosticism, Marcion, and Montanism; each of these respective theological battles pushed the church to develop a canon of scripture. Lee McDonald argues that while it is overbearing to say that Marcion created the New Testament, his influence in hastening the development of the canon must not be overlooked. Concerning Gnosticism, Montanism, and heresy in general, McDonald concludes that the response of the early church was not a canon of sacred books, but the production of a “canon of faith.” John Barton argues that Marcion actually followed the orthodox example of developing a collection of authoritative books and thus was in no way truly formative in the development of the Christian canon, thus presenting a view that is diametrically opposed to Campenhausen. J. N. D. Kelly argues that the essential contours of the canon were in place before the controversies, arguing that their impact was minimal as most. The prevailing modern view concerning the role of heretics on the formation of the canonical scriptures seems to be primarily that of McDonald and Barton, that while the Marcionite, Gnostic, and Montanist conflicts certainly had an impact upon Christian theology and the role of the canon, the form of the books viewed as scripture seems to have been roughly intact prior to the controversies, thereby making the impact of the heretics slight at most. Though this position is hotly debated in some realms, it seems to represent the growing scholarly consensus.
 Ibid, 147-209. One must note Von Campenhausen’s perspective on the importance of Irenaeus’ response to Marcion in the development of the canon.  Ibid., 163.  Bruce M. Metzger, The Canon of the New Testament: It’s Origin, Development, and Significance, Clarendon Press, Oxford, 1992, 75-112.  Lee Martin McDonald, The Biblical Canon: Its Origins, Transmission, and Authority, Hendrickson Publishers, Peabody, MA, 2007, 324-333.  Ibid., 333-342.  John Barton, Holy Writings, Sacred Text: The Canon in Early Christianity, Westminster John Knox Press, Louisville, 1997, 35-62.  J.N.D. Kelly, Early Christian Doctrines, Fifth Ed. Continuum, London, 2009, 56-58. Note: For more on the topic of Marcion’s impact on the formation of the canon, please see Prahlow, “Discerning Witnesses” (Wake Forest, 2014).