St. Irenaeus of Lyons

Irenaeus was born around the year 130, most likely in Smyrna in Asia Minor, and as a boy he heard the bishop Polycarp preach — Polycarp who had himself received the faith directly from the apostle John. This chain — from the apostle to his disciple to the young Irenaeus listening in the congregation — became the foundation of everything he later wrote: the faith is not hidden or esoteric, but delivered openly from Christ through the apostles to the churches they planted, and through those churches to us.

He moved westward, eventually coming to the church at Lugdunum — present-day Lyon in Gaul — where he served as presbyter and then bishop. In 177 he was in Rome carrying letters when the great persecution swept Lyon, claiming nearly fifty of the congregation including the bishop Pothinus. On his return he was elected to succeed Pothinus.

The defining labor of his episcopate was the refutation of Gnosticism. The Gnostic teachers — Valentinus, Marcion, Basilides — taught that the Creator of the material world was a lesser or evil deity, that Christ had not truly become flesh, and that salvation consisted of secret knowledge reserved for an enlightened few. Against all of this Irenaeus wrote his great work Adversus Haereses (Against Heresies) in five books. But he did not merely refute: he was the first theologian to articulate the "recapitulation" of all things in Christ — that the Son of God, by taking on the whole of human life from birth to death, summed up and healed what Adam had broken, restoring humanity's original vocation to grow into the divine likeness.

Irenaeus reposed around the year 202, and he is venerated as a martyr, though the circumstances of his death are unrecorded. His other surviving work, the Demonstration of the Apostolic Preaching, is the earliest extant catechetical summary of the Christian faith addressed to those outside the Church. His feast in the Orthodox Church falls on August 23.