Based on the arguments Irenaeus made in support of only four authentic gospels, some interpreters deduce that the "fourfold Gospel" must have still been a novelty in Irenaeus' 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." (The apologist and ascetic Tatian had previously harmonized the four gospels into a single narrative, the "Diatesseron" circa 150–160)