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,
Development of the New Testament canon as now known): In the mid-2nd century, Justin Martyr (whose writings span the period from c. 145 to 163) mentions the "memoirs of the apostles", which Christians called "gospels" and which were regarded as on par with the Old Testament. Scholars are divided on whether there is any evidence that Justin included the Gospel of John among the "memoirs of the apostles", or whether, on the contrary, he based his doctrine of the Logos on it. Justin quotes the letters of Paul, 1 Peter, and Acts in his writings. In Justin's works, distinct references are found to Romans, 1 Corinthians,