Irenaeus was the bishop of Lugdunum (Lyons) and was one of the leading theologians of the 2nd century (AD 103-202). He was a student under Polycarp, who was a Christian bishop of Smyrna. Eventually, he moved to Rome and studied under Justin Martyr, who was an early Christian apologist. According to early church historian Eusebius, Irenaeus had served as a missionary to southern Gaul.
In AD 177, Roman Emperor Marcus Aurelius initiated a persecution of Christians in France. In this persecution, the church bishop of Lyons died, which left the office of bishop open. Irenaeus escaped this persecution because he was en route to Rome, but, when he returned to France in 178, he became the next bishop of Lyons. During his role as bishop, Irenaeus combatted two rising heresies, Marcionism and Gnosticism, in his large work Adversas Haereses (Against Heresies). Further, he was an advocate of apostolic succession and appropriate biblical preaching, which he elaborated on in The Proof of Apostolic Preaching. He was persecuted and died around 202, but his work is forever remembered in the church.
Irenaeus lived three generations after Jesus was on earth. In this time, the early church was widely expanding and tension was present within the various factions of the church. For example, within the church at large, there was debate over when to celebrate festivals. The churches in Asia Minor insisted upon celebrating Easter on the same date as the Jews celebrating Passover. On the other hand, the Roman Catholics argued that Easter should be celebrated on Resurrection Sunday. In his role as bishop, Irenaeus needed to be the mediator between the contending factions.
Beyond inner church disagreements, heresy was making its way into the church. Two major heresies were afoot: Marcionism and Gnosticism. Marcion was a schismatic leader in Rome who promoted dualism, teaching that the God of the Old Testament was different than the God of the New Testament. Further, he did not hold to the hypostatic union because he believed that Jesus only appeared to be human but was not truly a man. Gnosticism was very similar to Marcionism because it also promoted dualism, focusing on a separation between the material and the spiritual. This dualistic attitude led to a negative view towards Creator God and the material human body, and led to positive view towards the spiritual self. Both Marcionism and Gnosticism denied Jesus’s full humanity and divinity, which further led to the disbelief in his saving work on the cross.
Irenaeus is well-known for his work Adversus Haereses. This discourse, composed of five different books, attacked the heretical teachings of Marcionism and Gnosticism. In this work, Irenaeus asserted the validity of the Old Testament, or the Jewish Bible at the time. This was critical in this period because the canon of the entire Bible was being developed. Irenaeus made it clear that Gnostic writings did not claim scriptural authority. Further, Irenaeus quoted from every single New Testament book (except 3 John), which further ensured the church’s acceptance of New Testament scripture.
Irenaeus upheld the Roman Catholic idea of apostolic succession. This is the tradition that bishops can trace their succession back to the apostles. This practice was contrary to Gnostic practices because Gnostics believed that they obtained some sort of hidden, secret knowledge that had been passed down from Jesus. In attempt to safeguard orthodoxy, apostolic succession ensured that bishops could trace their teaching back to the apostles, who received their teaching from Jesus.
Further, Irenaeus discussed his theory of recapitulation, which is perhaps his most well-known teaching. Unlike the heretical disbelief in the hypostatic union, recapitulation taught that Jesus was indeed human. His humanity was necessary in order for him to truly be the second Adam who would redeem what the first Adam failed at. Jesus’s full humanity and divinity were necessary in order for him to redeem humanity and ensure their salvation.
Irenaeus’s second work is not as well-known as his first work, yet it was still significant for the early church. The Proof of Apostolic Preaching was a summary of Christian preaching, emphasizing that Christ truly fulfilled Old Testament prophecy. This had ties with his first work, which firmly upheld the work of the the Old Testament.
Irenaeus’s Lasting Significance
Irenaeus faced persecution and died around 202. His life was fully dedicated to being a servant in God’s kingdom. His various discourses combatted heresy and helped to propel the canonization of the 66 books of the Bible to completion. He advocated to maintain orthodoxy and fully affirmed the hypostatic union. The Church today must learn from Irenaeus’s great work in the church. We must emulate a similar zeal for orthodoxy and fight false teaching.