c. 180 AD
St. Irenaeus of Lyons, bishop of Lyons and disciple of St. Polycarp, wrote 'Against Heresies' (Adversus Haereses), a five-volume refutation of Gnosticism. He established the principle of apostolic succession β that true doctrine is preserved through the unbroken line of bishops tracing back to the apostles. He wrote: 'It is in our power to enumerate those who were appointed bishops by the apostles and their successors down to our own time.'
Irenaeus developed the concept of recapitulation β that Christ summed up (recapitulated) all of human history in Himself, undoing the damage of Adam's sin. He also argued for the canonical status of the four Gospels, writing that 'there cannot be more or fewer than four Gospels.' He was martyred during the persecution of Marcus Aurelius. Key writings: Against Heresies, Demonstration of the Apostolic Preaching