Development of the New Testament canon a novelty in Irenaeus's time. "Against Heresies" 3.11.7 acknowledges that many heterodox Christians use only one gospel while 3.11.9 acknowledges that some use more than four. The success of Tatian's Diatessaron in about the same time period is "...a powerful indication that the fourfold Gospel contemporaneously sponsored by Irenaeus was not broadly, let alone universally, recognized." Irenaeus apparently quotes from 21 of the New Testament books and names the author he thought wrote the text. He mentions the four gospels, Acts, the Pauline epistles with the exception of Hebrews and Philemon, as well as the first epistle of Peter, and
New Testament the Gospel of Matthew, though most assert Jewish-Christian authorship. Authorship is an area of longstanding and current research and debate, with different works posing different problems for identification. While the various works have traditional ascriptions of authorship, these ascriptions are in some cases defended by scholars, and in other cases disputed or rejected. According to many (if not most) critical scholars, none of the authors of the Gospels were eyewitnesses or even explicitly claimed to be eyewitnesses. Bart Ehrman of the University of North Carolina has argued for a scholarly consensus that many New Testament books were not written by