Irenaeus (c. 2nd century) was born somewhere in western Asia Minor, probably Smyrna. He studied religion and philosophy under Polycarp, the bishop of Smyrna. He was a missionary to Gaul, or modern-day France, and eventually became the bishop of Lyons when the previous bishop was martyred during the reign of Marcus Aurelius. He served with great distinction and there are indications that most of the population of Lyons accepted the message of Christ during his lifetime. He wrote extensively, including his best-known treatise, Against All Heresies, which defended the true faith against Gnosticism. He was the first early church Father to extensively use the entire New Testament in his writings and to show the unity between the Old and New Testaments.
