“Some popular writers today have spoken of scores of ancient ‘gospels’ competing with the canonical gospels until purged by Constantine. This claim is either disingenuous or stems from ignorance of the facts.”
“If we count as a ‘gospel’ any ‘life of Jesus’ regardless of the date of its composition, we would have to include the plethora of nineteenth-century ‘lives of Jesus’ (along with a few movies about Jesus today). Clearly, however, the only ‘lives of Jesus’ that can be counted onto give us independently reliable information are those that were composed within the earliest generations of the church. As we shall argue, of the ‘gospels’ that survive today, for better or for worse only the four preserved and accepted by the mainstream second-century church into their functioning canon can lay a solid claim to stem from the first few generations (i.e., from the first century, although the Fourth Gospel probably meets this criterion by less than a decade).”
“One can in fact find scores of extant (most of them barely extant) works that can be called ‘gospels,’ but only a few of these date even to the second century, and many stem from long after Constantine.”
“The popular claim is also disingenuous because matters were settled for the vast majority of the church long before Constantine. By 170 CE, Tatian in Syria harmonized the four gospels now accepted as canonical, probably developing earlier work from the mid-second century. From the same generation Irenaeus in the western Empire, far from Syria and addressing a culturally quite different form of the Christian movement than Tatian addressed, also emphasized these four gospels. Toward the end of the second century, Irenaeus treats Matthew, Mark, Luke and John as the only gospels universally accepted by the ‘orthodox’ circle of churches. Irenaeus’ modern detractors may dispute his claims about how early these works were accepted, but they were certainly widely accepted by his day, and to place other works on an equal footing with the four as late as Constantine is simply inaccurate, C. Keener, The Historical Jesus of the Gospels (Eerdmans 2009), 48-49.