Irenaeus answered Gnostics with scripture, tradition and bishops
Second-century Greek bishop Irenaeus of Lyon fought Gnostic secret-wisdom claims by naming three pillars of orthodoxy: the scriptures, apostolic tradition and the teaching church. Around 180 he wrote Against Heresies, especially targeting Valentinus’s elaborate cosmic system and its promise of hidden knowledge.
Irenaeus grew up in Smyrna, today's İzmir, the hometown of the martyr Polycarp, and was born before Polycarp died around 155. Unusually for his era he was raised Christian rather than converting as an adult. He was serving as a priest in Lyon when Christians there were persecuted under Marcus Aurelius; in 177 the jailed clergy sent him to Rome with a letter to Pope Eleutherius about the Montanist movement, and on his return he became the city's bishop.
His great book answered Greek merchants who had begun preaching in his diocese that the material world was the botched work of an evil god, to be escaped through secret knowledge. Irenaeus replied that true knowledge is knowledge of Christ, which redeems creation instead of fleeing it. Book I traces the Valentinians back to Simon Magus; later books try to dismantle their doctrine. Until the Nag Hammadi library surfaced in 1945, his account was the fullest surviving description of Gnostic belief, and most scholars now judge it fairly accurate despite its polemic tone.
He also helped fix what counted as scripture. Before him, communities favoured different gospels, with Anatolian Christians preferring John and Matthew the most popular overall; Irenaeus insisted on exactly four. He is the earliest writer to credit the fourth gospel to John the Apostle and the third to Luke, Paul's companion. He cites the New Testament roughly 1,000 times, drawing on 21 of its 27 books, about a third of the citations from Paul.
Only one other work survives whole, the Demonstration of the Apostolic Preaching, found in an Armenian copy in 1904. Around 190 he persuaded Pope Victor I not to excommunicate Anatolian churches over their Easter date. His death date is unknown, and his burial church in Lyon was wrecked by Huguenots in 1562. Pope Francis named him the 37th Doctor of the Church in January 2022, with the extra title Doctor of Unity.
Source: Irenaeus
