Irenaeus of Lyons was a grandson in the faith of the apostle John. Jesus taught John. John taught Polycarp. Polycarp taught Irenaeus. Only two lives stand between Irenaeus and the Lord's own disciple, and that short chain is the heart of why his writings matter so much.
The chain: from John to Polycarp to Irenaeus
Paul told Timothy, “the things that thou hast heard of me among many witnesses, the same commit thou to faithful men, who shall be able to teach others also” (2 Timothy 2:2). That is four generations in one verse: Paul, Timothy, faithful men, and others also. Irenaeus is a living example of that verse.
- John, the disciple whom Jesus loved, wrote “that which we have seen and heard declare we unto you” (1 John 1:3). The early church remembered that after his exile on Patmos (Revelation 1:9) he lived in Ephesus into the reign of the emperor Trajan, about AD 100.
- Polycarp, born around AD 69, was a disciple of John and became overseer of the church at Smyrna, near Ephesus. He was martyred about AD 155 at the age of eighty-six. (Read more: Polycarp of Smyrna.)
- Irenaeus, born around AD 130 in Asia Minor, probably in Smyrna itself, heard Polycarp preach as a boy.
Decades later, Irenaeus wrote to a boyhood friend named Florinus, who had drifted into false teaching. He reminded him of the old man they had both heard:
“I am able to describe the very place in which the blessed Polycarp sat as he discoursed, and his goings out and his comings in, and the manner of his life, and his physical appearance, and his discourses to the people, and the accounts which he gave of his intercourse with John and with the others who had seen the Lord.”
Irenaeus said he remembered it better than things that had happened recently, and that Polycarp's teaching about Jesus was all “in harmony with the Scriptures.” He also mentions Papias, “the hearer of John, and a companion of Polycarp.” For Irenaeus, the apostle John was not a distant figure from long ago. He was the teacher of his own teacher.
From Asia to Gaul, and through the fire
Irenaeus later moved west to Lyons in Gaul (modern France), where a church of believers from Asia had taken root under its aged overseer Pothinus. In AD 177, persecution broke out. Pothinus, over ninety, died in prison, and many believers, including the slave girl Blandina, were tortured and killed in the arena. (Read more: The Martyrs of the Early Church.) Irenaeus had been sent to Rome with a letter from the imprisoned believers. When he returned, he became overseer of Lyons in Pothinus's place.
Against Heresies: no secret gospel
The great danger of Irenaeus's day was Gnosticism: teachers who said the God of the Old Testament was a lesser, flawed god, that the material world was evil, that Jesus did not truly come in the flesh, and that salvation came through a secret knowledge (gnosis) handed down privately to a spiritual elite.
Around AD 180, Irenaeus answered them in five books usually called Against Heresies. His answer comes straight out of that chain of teachers:
- The apostles hid nothing. If they had known secret mysteries, Irenaeus argued, they would have handed them to the men they trusted most with the churches. Instead they taught openly, and their teaching is written in the Scriptures.
- We can name the teachers. The churches could list the men who had led them since the apostles, and Irenaeus does exactly that for the church in Rome. Then he points to Polycarp, “whom I also saw in my early youth,” who “always taught the things which he had learned from the apostles.” He adds that the church in Ephesus, “having John remaining among them permanently until the times of Trajan, is a true witness of the tradition of the apostles.”
- The teaching matches everywhere. Churches spread from Gaul to Asia to Africa all confessed the same faith in one God, the Maker of heaven and earth, and in one Christ Jesus, the Son of God, who became flesh for our salvation. The secret teachers could not agree with each other, let alone with the apostles.
This is what Irenaeus meant by succession: an unbroken line of witnesses, known by name, who received the apostles' teaching and passed it on unchanged, so that anyone could check what the apostles taught. Christians today understand “apostolic succession” in different ways. Roman Catholic and Orthodox Christians see in it a line of ordained bishops who carry the apostles' authority. Most Protestants see it as a succession of the apostles' doctrine, which every teacher must be tested by, and point to Irenaeus's own appeal to the Scriptures. Either way, Irenaeus's point against the Gnostics was simple and powerful: the true faith is the public faith of the apostles, “the faith which was once delivered unto the saints” (Jude 3), not a secret one.
What else we owe him
- The four Gospels. Irenaeus is our earliest writer to insist plainly that there are four Gospels, no more and no fewer: Matthew, Mark, Luke and John. He tells us that John, “the disciple of the Lord, who also had leaned upon His breast,” wrote his Gospel while living at Ephesus.
- The whole Bible as one story. Against teachers who cut the Old Testament away from the New, Irenaeus showed one God and one plan from creation to the cross to the new creation. Christ is the second Adam who undid what the first Adam did (Romans 5:12–19), gathering “together in one all things in Christ” (Ephesians 1:10).
- A God who gives life. One of his best-known lines: “For the glory of God is a living man; and the life of man consists in beholding God.”
- A peacemaker. His name means “peaceful,” and he lived up to it. When a bishop of Rome, Victor, threatened to cut off the churches of Asia over the date of Easter, Irenaeus wrote to urge him to keep the peace, reminding him that Polycarp and Anicetus had disagreed on the same question and still shared the Lord's Supper together.
Irenaeus died around AD 202. Later writers called him a martyr, but the earliest sources do not tell us how he died.
Why it matters for us
When people today claim a “lost” or “hidden” gospel that changes who Jesus is, they are making the same claim the Gnostics made, and Irenaeus's answer still stands. The faith of the Bible was not invented later or kept secret. It was taught openly by eyewitnesses, written down in the Scriptures, and handed from John to Polycarp to Irenaeus and on to us. And every believer is part of that chain: someone handed the faith to you, and you are called to hand it on to faithful people “who shall be able to teach others also” (2 Timothy 2:2).
Quotations from Irenaeus are from the Ante-Nicene Fathers (1885); his letter to Florinus is from Eusebius's Church History 5.20 (1890 translation). Both are public domain.