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
New Testament Writings attributed to the apostles circulated among the earliest Christian communities and the Pauline epistles were circulating, perhaps in collected forms, by the end of the 1st century AD. One of the earliest attempts at solidifying a canon was made by Marcion, "circa" 140 AD, who accepted only a modified version of Luke (the Gospel of Marcion) and ten of Paul's letters, while rejecting the Old Testament entirely. His canon was increasingly rejected by other groups of Christians, notably the proto-orthodox Christians, as was his theology, Marcionism. Adolf Harnack in "Origin of the New Testament" (1914) observed that the church