He was one of the first Fathers and he was the first great theologian of the Church, yet St. Irenaeus is hardly a household name among practicing Catholics today.
And perhaps understandably so. The distance between his time and ours—about 18 centuries—doesn’t help. He lived at a time when a common path to sainthood was martyrdom—leaving us with stories of grisly death and heroic virtue that still reverberate down the centuries. But Irenaeus himself seems to have been spared the sword and the lions. He’s also left us just one work—and one that’s not exactly inviting to the layman. If its formal title, Refutation and Overthrow of Knowledge falsely So-called, doesn’t scare off the novice, the hundred-pages detour it takes through the bizarre parallel universe of Gnostic gods and demi-gods might.
Yet Irenaeus remains enormously important to the Church today—not only for professional theologians but also for devout Catholics who want to better understand and defend their faith. Here are ten things you need to know about him.
1. Spiritual lineage back to the Apostle John. Irenaeus was born sometime around 125 and died at the end of that century or the beginning of the next. He thus lived close to the time of the apostles and, according to tradition, his theology was shaped by the preaching of Polycarp, who was himself a disciple of the Apostle John. By simply being a Church Father, Irenaeus is an authoritative figure—this only makes him more so.
2. Refuter of Gnostic heresies. Gnosticism—a heresy which came in many shapes and sizes and denied a whole slew of Christian doctrines, from the goodness of creation to the fully divinity of Christ—was the first heresy the Christian world confronted. Irenaeus offers a meticulous and theologically rich refutation of Gnosticism in his major work, better known as Against Heresies. Although Irenaeus sets out to debate heretics, along the way he produced one of the first great systematic theological treatises of the Church.
3. Eucharistic belief. Irenaeus is a crucially important source for establishing the existence of belief in the Real Presence of Christ in the Eucharist among the earliest Christians. The Eucharist, Irenaeus writes, consists of “two realities, earthly and heavenly.” He describes Christ as the “perfect bread” of the Father who enables us to enter into full communion with the being of God: “He did this when He appeared as a man, that we, being nourished, as it were, from the breast of His flesh, and having, by such a course of milk nourishment, become accustomed to eat and drink the Word of God, may be able also to contain in ourselves the Bread of immortality, which is the Spirit of the Father.” These are not the words of someone who views the Eucharist as a symbol—and remember this is in the second century of the Church.
4. Marian devotion. Mary also plays a central role in his theology. In Against Heresies, Irenaeus compares her to Eve: “And if the former did disobey God, yet the latter was persuaded to be obedient to God, in order that the Virgin Mary might become the patroness (advocata) of the virgin Eve. And thus, as the human race fell into bondage to death by means of a virgin, so is it rescued by a virgin; virginal disobedience having been balanced in the opposite scale by virginal obedience.”
5. Scriptural canon. Irenaeus provides us with one of the first lists of the four gospels. His argument for why there were four—and no more—is among the more intriguing arguments in defense of the biblical canon ever put forth: “It is not possible that the Gospels can be either more or fewer in number than they are. For, since there are four zones of the world in which we live, and four principal winds, while the Church is scattered throughout all the world, and the ‘pillar and ground’ of the Church is the Gospel and the spirit of life; it is fitting that she should have four pillars, breathing out immortality on every side, and vivifying men afresh.”
6. Centrality of the Church. Irenaeus also had a high view of the Church’s role in the world. At one point, he likens it to a recreation of the Garden of Eden: “For the Church has been planted as a garden (paradisus) in this world; therefore says the Spirit of God, ‘Thou mayest freely eat from every tree of the garden,’ that is, Eat ye from every Scripture of the Lord; but ye shall not eat with an uplifted mind, nor touch any heretical discord.’” Remember—this is coming centuries before the Church reached the height of its power and influence in the Middle Ages.
8. Unity through the Roman Church. Already, in the second century, Irenaeus had a clear notion of how unit was maintained in the universal Church. In an oft-quoted passage, he insists on the need for communion with the Church in Rome:
Since, however, it would be very tedious, in such a volume as this, to reckon up the successions of all the Churches, we do put to confusion all those who, in whatever manner, whether by an evil self-pleasing, by vainglory, or by blindness and perverse opinion, assemble in unauthorized meetings; by indicating that tradition derived from the apostles, of the very great, the very ancient, and universally known Church founded and organized at Rome by the two most glorious apostles, Peter and Paul; as also the faith preached to men, which comes down to our time by means of the successions of the bishops. For it is a matter of necessity that every Church should agree with this Church, on account of its pre-eminent authority, that is, the faithful everywhere, inasmuch as the apostolical tradition has been preserved continuously by those who exist everywhere.
9. All things summed up in Christ. Irenaeus is also famous for recapitulation, the concept that all things are summed up, or, literally, brought back to their head, which is Christ. This may sound like an abstract theological term, but it makes a real difference in how we understand Who Christ was and what He did on earth. In his theology of recapitulation, Irenaeus is really saying that Christ, in a sense, re-enacted all the events and all the figures from the Garden of Eden, in the process of undoing original sin. Just as tree was the cause of the curse, Irenaeus writes, so also we were saved through a tree (the cross). And just as Christ is the new Adam, so also Mary is the new Eve. Irenaeus even sees a parallel between the temptation of Eve by the serpent and the temptation of Christ in the desert by Satan. Recapitulation, properly understand, also becomes an argument for the fullness of Christ’s humanity and divinity.
10. Original sin. Irenaeus is also an important early source for the doctrine of original sin, even though he does not use that term. Irenaeus defines the original sin as disobedience and explains why death was a necessary consequence. Also, again with insight that is remarkable for such an early writer, Irenaeus demonstrates how original sin, which the result of free will, nonetheless fit into his ultimate plan for humanity.
Want to learn more about Irenaeus? Begin by reading Against Heresies. NewAdvent.org has a helpful table of contents that will help you navigate your way through this book.