Today, the Church remembers St. Irenaeus (died about AD 202) who was a Greek Christian priest noted for his role in guiding and expanding Christian communities in what is now the south of France and, more widely, for the development of Christian theology by combatting what the Early Church was beginning to define as heresy and defining orthodoxy. Originating from Smyrna, now Izmir in Turkey, he had heard the preaching of Polycarp, who in turn was said to have heard John the Evangelist, an apostle of Jesus.
Chosen as bishop of Lugdunum, now Lyon, his best-known work is "On the Detection and Overthrow of the So-Called Gnosis", often cited as "Adversus Haereses", an attack on gnosticism, in particular that of Valentinus. To counter the doctrines of the gnostic sects claiming secret wisdom, he offered three pillars of orthodoxy: the scriptures, the tradition handed down from the apostles, and the teaching of the apostles' successors. Intrinsic to his writing is that the surest source of Christian guidance is the church of Rome, and he is the earliest surviving witness to recognise all four gospels as essential. Irenaeus is also known as one of the first theologians to use the principle of apostolic succession to refute his opponents. Irenaeus' point when refuting the Gnostics was that all of the Apostolic churches had preserved the same traditions and teachings in many independent streams. It was the unanimous agreement between these many independent streams of transmission that proved the orthodox Faith, current in those churches, to be true.
The central point of Irenaeus' theology is the unity and the goodness of God. Irenaeus conceives of our salvation as essentially coming about through the incarnation of God as a man. He characterizes the penalty for sin as death and corruption. God, however, is immortal and incorruptible, and simply by becoming united to human nature in Christ he conveys those qualities to us: they spread, as it were, like a benign infection. Irenaeus emphasizes that salvation occurs through Christ's Incarnation, which bestows incorruptibility on humanity, rather than emphasizing His Redemptive death in the crucifixion (although the latter event is an integral part of the former).
Blessed Irenaeus, ora pro nobis.
Almighty God, you upheld your servant Irenaeus with strength to maintain the truth against every blast of vain doctrine: Keep us, we pray, steadfast in your true religion, that in constancy and peace we may walk in the way that leads to eternal life; through Jesus Christ our Lord, who lives and reigns with you and the Holy Spirit, one God, now and for ever. Amen.
