Irenaeus of Lyons

Irenaeus was bishop of Lyons in Gaul and, as a young man, had heard the preaching of Polycarp of Smyrna, who had himself known the Apostle John — a living link the Church has long pointed to as evidence of unbroken apostolic teaching. His major work, Against Heresies, refutes Gnostic teaching by appealing to the public, traceable succession of bishops from the apostles, making him one of the earliest and most systematic witnesses to apostolic tradition.