Irenaeus cites from most of the [[New Testament]] canon, as well as works from the [[Apostolic Fathers]], [[I Clement]] and the [[Shepherd of Hermas]], however he makes no references to [[Book of Philemon|Philemon]], [[II Peter]], [[III John]] and [[Book of Jude|Jude]], which isn't surprising, since the canon of the [[Holy Scriptures]] had not yet been set. Irenaeus was the first Christian writer to list all four and exactly four of the canonical [[Gospel]]s as divinely inspired, possibly in reaction to [[Marcion]]'s edited version of [[Gospel of Luke|Luke]], which Marcion asserted was the one and only true gospel.

==His theology==