Irenaeus was in all probability born in Smyrna (today, Izmir in Turkey) in about 135-140, 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. In that very year, he was sent to Rome bearing a letter from the community in Lyons to Pope Eleutherius. His mission to Rome saved Irenaeus from the persecution of Marcus Aurelius which took a toll of at least 48 martyrs, including the 90-year old Bishop Pontinus of Lyons, who died from ill-treatment in prison. Thus, on his return Irenaeus was appointed Bishop of the city. The new Pastor devoted himself without reserve to his episcopal ministry which ended in about 202-203, perhaps with martyrdom.
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. The second-century Church was threatened by the so-called Gnosis, a doctrine which affirmed that the faith taught in the Church was merely a symbolism for the simple who were unable to grasp difficult concepts; instead, the initiates, the intellectuals - Gnostics, they were called - claimed to understand what was behind these symbols and thus formed an elitist and intellectualist Christianity. Obviously, this intellectual Christianity became increasingly fragmented, splitting into different currents with ideas that were often bizarre and extravagant, yet attractive to many. One element these different currents had in common was "dualism": they denied faith in the one God and Father of all, Creator and Saviour of man and of the world. To explain evil in the world, they affirmed the existence, besides the Good God, of a negative principle. This negative principle was supposed to have produced material things, matter.
Firmly rooted in the biblical doctrine of creation, Irenaeus refuted the Gnostic dualism and pessimism which debased corporeal realities. He decisively claimed the original holiness of matter, of the body, of the flesh no less than of the spirit. 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; he himself speaks of the system of theology, that is, of the internal coherence of all faith. At the heart of his doctrine is the question of the "rule of faith" and its transmission. For Irenaeus, the "rule of faith" coincided in practice with the Apostles' Creed, which gives us the key for interpreting the Gospel, for interpreting the Creed in light of the Gospel. The Creed, which is a sort of Gospel synthesis, helps us understand what it means and how we should read the Gospel itself.
In fact, the Gospel preached by Irenaeus is the one he was taught by Polycarp, Bishop of Smyrna, and Polycarp's Gospel dates back to the Apostle John, whose disciple Polycarp was.
The true teaching, therefore, is not that invented by intellectuals which goes beyond the Church's simple faith. The true Gospel is the one imparted by the Bishops who received it in an uninterrupted line from the Apostles. They taught nothing except this simple faith, which is also the true depth of God's revelation. Thus, Irenaeus tells us, there is no secret doctrine concealed in the Church's common Creed. There is no superior Christianity for intellectuals. The faith publicly confessed by the Church is the common faith of all. This faith alone is apostolic, it is handed down from the Apostles, that is, from Jesus and from God. In adhering to this faith, publicly transmitted by the Apostles to their successors, Christians must observe what their Bishops say and must give special consideration to the teaching of the Church of Rome, pre-eminent and very ancient. It is because of her antiquity that this Church has the greatest apostolicity; in fact, she originated in Peter and Paul, pillars of the Apostolic College. All Churches must agree with the Church of Rome, recognizing in her the measure of the true Apostolic Tradition, the Church's one common faith. With these arguments, summed up very briefly here, Irenaeus refuted the claims of these Gnostics, these intellectuals, from the start. First of all, they possessed no truth superior to that of the ordinary faith, because what they said was not of apostolic origin, it was invented by them. Secondly, truth and salvation are not the privilege or monopoly of the few, but are available to all through the preaching of the Successors of the Apostles, especially of the Bishop of Rome. In particular - once again disputing the "secret" character of the Gnostic tradition and noting its multiple and contradictory results - Irenaeus was concerned to describe the genuine concept of the Apostolic Tradition which we can sum up here in three points.
a) Apostolic Tradition is "public", not private or secret. Irenaeus did not doubt that the content of the faith transmitted by the Church is that received from the Apostles and from Jesus, the Son of God. There is no other teaching than this. Therefore, for anyone who wishes to know true doctrine, it suffices to know "the Tradition passed down by the Apostles and the faith proclaimed to men": a tradition and faith that "have come down to us through the succession of Bishops" (Adversus Haereses, 3, 3, 3-4). Hence, the succession of Bishops, the personal principle, and Apostolic Tradition, the doctrinal principle, coincide.
b) Apostolic Tradition is "one". Indeed, whereas Gnosticism was divided into multiple sects, Church Tradition is one in its fundamental content, which - as we have seen - Irenaeus calls precisely regula fidei or veritatis: and thus, because it is one, it creates unity through the peoples, through the different cultures, through the different peoples; it is a common content like the truth, despite the diversity of languages and cultures. A very precious saying of St Irenaeus is found in his book Adversus Haereses: "The Church, though dispersed throughout the world... having received [this faith from the Apostles]... as if occupying but one house, carefully preserves it. She also believes these points [of doctrine] just as if she had but one soul and one and the same heart, and she proclaims them, and teaches them and hands them down with perfect harmony as if she possessed only one mouth. For, although the languages of the world are dissimilar, yet the import of the tradition is one and the same. For the Churches which have been planted in Germany do not believe or hand down anything different, nor do those in Spain, nor those in Gaul, nor those in the East, nor those in Egypt, nor those in Libya, nor those which have been established in the central regions of the world" (1, 10, 1-2). Already at that time - we are in the year 200 - it was possible to perceive the Church's universality, her catholicity and the unifying power of the truth that unites these very different realities, from Germany, to Spain, to Italy, to Egypt, to Libya, in the common truth revealed to us by Christ.
c) Lastly, the Apostolic Tradition, as he says in the Greek language in which he wrote his book, is "pneumatic", in other words, spiritual, guided by the Holy Spirit: in Greek, the word for "spirit" is "pneuma". Indeed, it is not a question of a transmission entrusted to the ability of more or less learned people, but to God's Spirit who guarantees fidelity to the transmission of the faith.
This is the "life" of the Church, what makes the Church ever young and fresh, fruitful with multiple charisms.
For Irenaeus, Church and Spirit were inseparable: "This faith", we read again in the third book of Adversus Haereses, "which, having been received from the Church, we do preserve, and which always, by the Spirit of God, renewing its youth as if it were some precious deposit in an excellent vessel, causes the vessel itself containing it to renew its youth also.... For where the Church is, there is the Spirit of God; and where the Spirit of God is, there is the Church and every kind of grace" (3, 24, 1). As can be seen, Irenaeus did not stop at defining the concept of Tradition. His tradition, uninterrupted Tradition, is not traditionalism, because this Tradition is always enlivened from within by the Holy Spirit, who makes it live anew, causes it to be interpreted and understood in the vitality of the Church. Adhering to her teaching, the Church should transmit the faith in such a way that it must be what it appears, that is, "public", "one", "pneumatic", "spiritual". Starting with each one of these characteristics, a fruitful discernment can be made of the authentic transmission of the faith in the today of the Church. More generally, in Irenaeus' teaching, the dignity of man, body and soul, is firmly anchored in divine creation, in the image of Christ and in the Spirit's permanent work of sanctification. This doctrine is like a "high road" in order to discern together with all people of good will the object and boundaries of the dialogue of values, and to give an ever new impetus to the Church's missionary action, to the force of the truth which is the source of all true values in the world.
