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
Synoptic Gospels eighteenth century, when Johann Jakob Griesbach published in 1776 a "synopsis" of the synoptic gospels. Instead of harmonizing them, he displayed their texts side by side, making both similarities and divergences apparent. Griesbach, noticing the special place of Mark in the synopsis, hypothesized Marcan posteriority and advanced (as Henry Owen had a few years earlier) the two-gospel hypothesis (Matthew–Luke). In the nineteenth century, researchers applied the tools of literary criticism to the synoptic problem in earnest, especially in German scholarship. Early work revolved around a hypothetical proto-gospel ("Ur-Gospel"), possibly in Aramaic, underlying the synoptics. From this line of inquiry, however,