St. Irenaeus

June 28 is the feast of St. Irenaeus (c. 130-c. 202), bishop of Lyon and the first great Catholic theologian. Born at Smyrna, in Asia Minor, he was a disciple of Polycarp, who was himself a disciple of St. John — the chain of witness that Irenaeus records in his Against Heresies. He was sent from Smyrna to Lyon as a priest, and in 177, after the martyrdom of Bishop Pothinus in the persecution of Marcus Aurelius, he became the second bishop of Lyon.

His Detection and Overthrow of the So-Called Gnosis — usually Against Heresies — is the first work of Catholic theology. Written around 180, it refutes the Gnostic teachers who claimed a secret knowledge of Christ, and gives the first systematic statement of the rule of faith, the canon of Scripture, and the apostolic succession of bishops. His famous phrase — "the glory of God is a living man" — became the axiom of Catholic anthropology. Pope Pius X proclaimed him Doctor of the Church in 1907, and Pope Francis in 2022 declared him a Doctor of the Church with the title Doctor unitatis, doctor of unity.

Irenaeus is the patron of Lyon, where he was bishop and where, by tradition, he was martyred. The early feast was kept on June 28 in the East and in the Gallican calendars; the 1969 reform extended it to the universal Church. From Smyrna, where he learned the faith from Polycarp, to Lyon, where he wrote Against Heresies, the June 28 feast is the feast of the first Catholic theologian.