Gospel of Thomas in the late 2nd century that "since there are four quarters of the earth ... it is fitting that the church should have four pillars ... the four Gospels" ("Against Heresies", 3.11.8), and then shortly thereafter made the first known quotation from a fourth gospel—the canonical version of the Gospel of John. The late 2nd-century Muratorian fragment also recognizes only the three synoptic gospels and John. Bible scholar Bruce Metzger wrote regarding the formation of the New Testament canon, "Although the fringes of the emerging canon remained unsettled for generations, a high degree of unanimity concerning the greater part of
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