St. Irenaeus of Lyon
Patron of catechists, apologists
Saint Irenaeus (c. 130–202), bishop of Lyon, was a Greek from Smyrna and a disciple of Polycarp, who had himself been taught by the apostle John — so that the apostolic generation reached the Latin West through his memory. His five-book treatise Against the Heresies is the great Christian refutation of Gnosticism and the first complete summary of the rule of faith. He insisted that the Eucharist is the flesh of the Word and that humanity becomes truly itself only by 'recapitulation' in Christ. Tradition says he was martyred at Lyon in the persecution of Septimius Severus. Francis declared him a Doctor of the Church in 2022 with the title 'Doctor of Unity.'