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,
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