Irenaeus was born in Asia Minor around AD 130. He studied under Papias, as well as under Polycarp, bishop of Smyrna, who had been a disciple of the apostle John. He later moved to Rome, where he may have studied under Justin Martyr. Following the persecution by Marcus Aurelius, he travelled widely as a missionary, eventually arriving in Lyons, in southern France. From here he wrote a letter from the churches of Lyons and Vienne describing their sufferings which he took to the churches of Phrygia and Asia. On his return he was appointed bishop of Lyons in 177, where he rebuilt the church following the persecution, before finally being martyred in 195 during the reign of Emperor Setimius Severus.
Irenaeus is recognised as probably being the greatest Christian writer of the second century. He has become the best authority for the theology of the period, as well as for the heretical teachings of the time.
Many of his writings have been lost. However an Armenian translation of his Epideixis, or ‘Proof of Apostolic Preaching’ has been found. It was intended to be a handbook of apologetics, explaining Christian teaching, then proving its truth through the fulfilment of OT prophecy.
His most important work was ‘The Refutation of the False Gnosis’, commonly known as ‘Against Heresies’ written to defend the essential Christian doctrines and the historical roots of the faith against the heresies of the gnostic teacher Valentinus, and against Marcion. It is divided into five books. In the first two he exposes the heresy of the Gnostics, particularly the school of Valentinus. The second two give a constructive teaching of doctrine based on the canonical scriptures. In the final volume he explains the resurrection and the Last Things.
Irenaeus knew some of the disciples of Valentinus personally, and had read their commentaries. He described their teaching as "a glass imitation of the really genuine and highly prized emerald.
His main argument against the Gnostics was that the true tradition of Jesus and the Christian faith was to be found in the Gospels. This made him to become the first church father to recognise the four gospels, and only the four gospels, as canonical. He also referred to a list of apostolic writings. In his writings, he quoted from all of these, as well as from what is now the OT, referring to them all as ‘Scripture’.
Irenaeus traced the authority of the faith through a direct line of elders or bishops, like Polycarp, back to the original apostles, like John, thus helping to develop the doctrine of apostolic succession. As an example of this direct line of faithful preservation of the apostolic tradition, he listed the succession of bishops of Rome, beginning with Peter and Paul. In later years this opened the way for the church to elevate the bishop of Rome above all other bishops.
He opposed the gnostic understanding of creation by affirming that both the physical creation, and the work of redemption were both the actions of God. From the beginning, the creator God worked through his ‘two hands’, who were the Son and the Holy Spirit, without any angelic mediation. He understood the atonement as a ‘recapitulation’, that through his obedience Christ had reversed the failure of Adam, which became characteristic of the Eastern theory of salvation. He wrote that the destiny of mankind was to become like God. For this to happen the Logos or Son became human, summing up in himself all ages and classes of humanity.
He also described the Virgin Mary as the obedient Eve. He also taught that there would be an earthly millennial kingdom following the second coming of Christ. This is now known as the historic pre-millennial view.
Irenaeus was more of a theologian than a philosopher, being more biblical, with similarities with the teaching of Paul. In a similar way to the apologists, he attempted to explain the Christian tradition in the light of the secular knowledge of his day. Some see this Hellenisation of Christian doctrine to be a corruption of the Logos doctrine found in John’s Gospel.
His books include:
Against Heresies: To counteract Gnosticism
Proof of Apostolic Preaching: To show the fulfilment of the OT, a handbook of apologetics
On Knowledge: Address to the Greeks
Letter from churches of Lyons and Vienne to churches of Phrygia and Asia
Letter to Blastus On Schism
Letter to Florinus On Monarchy, or That God is not the Author of Evil.