New Testament the Anchor Bible Dictionary), may be the earliest known New Testament canon attributed to mainstream Christianity. It is similar, but not identical, to the modern New Testament canon. The oldest clear endorsement of Matthew, Mark, Luke, and John being the only legitimate gospels was written "circa" 180 AD. A four gospel canon (the "Tetramorph") was asserted by Irenaeus, who refers to it directly in his polemic "Against the Heresies", "It is not possible that the gospels can be either more or fewer in number than they are. For, since there are four zones of the world in which we live,
Gospel of Peter in the canonical gospels was transmitted orally, through readings in the churches, i.e. that the text is based on what the author "remembers" about the other gospels, together with his own embellishments. Ron Cameron and others have further speculated the Gospel of Peter was written independently of the synoptic gospels using an early proto-gospel. A consequence of this is the potential existence of a source text that formed the basis of the passion narratives in Matthew, Luke, and Mark, as well as in Peter. Origen makes mention of the Gospel of Peter as agreeing with the tradition of the Hebrews.