St. Irenaeus was a bishop who so thoroughly refuted a certain strain of heresy in his region that his words were used throughout the Church to guide the truth that has been handed on to us today.

He was born in 125 and was educated by St. Polycarp, who personally knew and learned from St. John. Irenaeus was sent as a missionary to what is now Lyons, France. Trading routes were leading to the development of that region, and the Church was growing there. Irenaeus was assigned to work as a priest under the bishop, St. Pothinus.

The region fell under a persecution and Irenaeus was chosen to travel to Rome to deliver a letter and speak with the pope about some matter. While he was away, Pothinus was killed, along with many of the other priests who worked with him. Irenaeus stayed in Rome until it was safe, and later he returned to Lyons as its new bishop.

He was bishop there for some 20 years, and expanded the Church in the area. He even spoke the native Celtic dialect instead of his own Greek. Certain deviations of the faith were spreading through the area, and Irenaeus was determined to refute them and guide his flock with the true faith. He learned every variation of the heresy and then explained all of the distorted beliefs in a large work that also described the true faith that came to him from the apostles and is contained in Scripture.

These heresies were from a strain of thought called Gnosticism, which seemed attractive to people because it claimed to offer them secret wisdom that was not available to everyone. Irenaeus said that he was determined to “strip the fox.” His work in defense of the faith spread rapidly and was used everywhere to refute gnostic belief, which was a major threat to the early faith.

It is believed that Irenaeus was martyred, but there is little evidence for this. He died around the year 202, and his relics rest in the reliquary chapel in the Basilica. His image is used here with permission from Catholic.org.

St. Irenaeus, you defended the early Church from secret sects and ensured the truth of our faith today—pray for us!