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
Jesus in 1 Timothy 3:16) than the canonical gospels do. In the undisputed Pauline letters, which were written earlier than the gospels, the words or instructions of Jesus are cited several times (1 Corinthians 7:10–11, 9:14, 11:23–25, 2 Corinthians 12:9). Some early Christian groups had separate descriptions of the life and teachings of Jesus that are not included in the New Testament. These include the Gospel of Thomas, Gospel of Peter, and Gospel of Judas, the Apocryphon of James, and many other apocryphal writings. Most scholars conclude that these are written much later and are less reliable accounts than the canonical