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,
Synoptic Gospels texts of the three synoptic gospels often agree very closely in wording and order, both in quotations and in narration. Most scholars ascribe this to "documentary dependence", direct or indirect, meaning the close agreements among synoptic gospels are due to one gospel's drawing from the text of another, or from some written source that another gospel also drew from. The synoptic problem hinges on several interrelated points of controversy: Furthermore, some theories try to explain the relation of the synoptic gospels to John; to non-canonical gospels such as Thomas, Peter, and Egerton; to the Didache; and to lost documents such