The importance of Irenaeus’s Against Heresies transcends its historical polemics against Gnosticism. In making a case against Valentinians, Irenaeus developed the theological groundwork for what would become orthodox Christianity. He desired to make the church truly “catholic” (universal) and, in doing so, formulated important principles, especially creed, canon, and apostolic succession. Apostolic succession was necessary to create a common discourse among Christians. A definite canon was important for having a shared set of texts from which all could draw. A creed was vital for summarizing what bound Christians together. Behind all Irenaeus’s polemics lay an intense pastoral desire for the welfare of the church.
It would therefore be misguided to see Irenaeus as a bullying bishop trying to force his beliefs on others. What he disliked about Gnosticism was its dual tendencies toward rampant individualism and toward elitism. Although superficially inclusive—Gnostics seemingly put few constraints on their adherents—they clearly thought of themselves as a superior minority. Irenaeus’s catholicism attempts to clear out a space whereby all can be a part of the church, not just a select few.
Irenaeus’s desire for unity within the church shapes his understanding of both Scripture and salvation. At a time in Christian history when the Old Testament could easily have been discarded, Irenaeus advocates its role within Christianity. Because he believes God to be eternal and singular, the story of God’s relationship with humans cannot begin with Jesus. Rather, Jesus functions as the climax and fulfillment of God’s work on earth. Humans participate in that story by believing in Jesus and experiencing salvation. When Irenaeus claims that salvation occurs through the church alone, he highlights the uniqueness of Christian teachings. If God is one, then God must have one method of relating to humans, and this is through Christ. Irenaeus’s exclusive claim for Christianity comes from his conviction of the unity of God. What might strike the modern reader as vitriol should not overshadow Irenaeus’s pastoral aims. Behind all his harsh language, he exhibits a capacious vision of what an ideal church might be.