Today we celebrate St. Irenaeus of Lyons. He was in all probability born in Smyrna (today, Izmir in Turkey), where in his youth, he attended the school of Bishop Polycarp, a disciple in his turn of the Apostle John. We do not know when he moved from Asia Minor to Gaul, but his move must have coincided with the first development of the Christian community in Lyons: here, in 177, we find Irenaeus listed in the college of presbyters.

Irenaeus was first and foremost a man of faith and a Pastor. Like a good Pastor, he had a good sense of proportion, a wealth of doctrine, and missionary enthusiasm. As a writer, he pursued a twofold aim: to defend true doctrine from the attacks of heretics, and to explain the truth of the faith clearly. His two extant works —the five books of “The Detection and Overthrow of the False Gnosis” and “Demonstration of the Apostolic Teaching” (which can also be called the oldest “catechism of Christian doctrine”)— exactly corresponded with these aims. In short, Irenaeus can be defined as the champion in the fight against heresies.

—But his work went far beyond the confutation of heresy: in fact, one can say that he emerges as the first great Church theologian who created systematic theology.