Development of the New Testament canon a novelty in Irenaeus's time. "Against Heresies" 3.11.7 acknowledges that many heterodox Christians use only one gospel while 3.11.9 acknowledges that some use more than four. The success of Tatian's Diatessaron in about the same time period is "...a powerful indication that the fourfold Gospel contemporaneously sponsored by Irenaeus was not broadly, let alone universally, recognized." Irenaeus apparently quotes from 21 of the New Testament books and names the author he thought wrote the text. He mentions the four gospels, Acts, the Pauline epistles with the exception of Hebrews and Philemon, as well as the first epistle of Peter, and
Development of the New Testament canon by lacking any passages that connected Jesus with the Old Testament. He believed that the god of Israel, who gave the Torah to the Israelites, was an entirely different god from the Supreme God who sent Jesus and inspired the New Testament. Marcion termed his collection of Pauline epistles the "Apostolikon". These also differed from the versions accepted by later Christian Orthodoxy. Marcion's list and theology were rejected as heretical by the early church; however, he forced other Christians to consider which texts were canonical and why. He spread his beliefs widely; they became known as Marcionism. In the introduction