You Should Know Irenaeus

Irenaeus of Lyons

Irenaeus once wrote,

Thou wilt not expect from me, who am resident among the Keltae, and am accustomed for the most part to use a barbarous dialect, any display of rhetoric, which I have never learned, or any excellence of composition, which I have never practiced, or any beauty and persuasiveness of style, to which I make no pretensions.1

As a result, Irenaeus has become a somewhat forgotten theologian, quickly dismissed as blundering and confused. Certainly, he is difficult to access, and hard-going theologians tend to incite the wrath of the critics. However, Emil Brunner’s reassessment of Irenaeus has become increasingly standard:

In spite of the fact that in the formal sense Irenaeus was not a systematic theologian, yet—like Luther—he was a systematic theologian of the first rank, indeed, the greatest systematic theologian: to perceive connections between truths, and to know which belongs to which. No other thinker was able to weld ideas together which others allowed to slip as he was able to do, not even Augustine or Athanasius.2

Who, then, was Irenaeus?

Theologians You Should Know

Michael Reeves

Reeves helps modern readers see that the lives and thought of important theologians from the past are still relevant today, shaping what we believe and how we live as Christians.

Irenaeus was born somewhere around AD 130 and grew up in Smyrna in Asia Minor, where the then bishop, Polycarp, became his mentor and passed on his memories of the apostle John and others who had seen the Lord. It was to be extremely important to Irenaeus that he had such a direct link back to the apostles. It is possible that he went with Polycarp to Rome—at any rate, both visited Rome. There Irenaeus seems to have learned from men such as Justin (he clearly borrowed much from him), as well as seeing how endemic the problem of heresy was there. He then traveled to Gaul and settled where a church had been founded quite recently in the capital city of Lugdunum (Lyons).

Then in 177 he was sent back as the church’s delegate to Eleutherus, then bishop of Rome, perhaps to discuss the problem of false teaching in Gaul. At any rate, while he was away, a ferociously violent wave of persecution swept through Lyons; many of Irenaeus’s friends and fellow-believers were horrifically tortured and killed, including the old bishop, Pothinus. When Irenaeus returned, he was chosen to succeed Pothinus as bishop.

After that, the only thing we know of Irenaeus’s life is his intervention in the Paschal controversy. Victor, Eleutherus’s successor as bishop of Rome, had threatened to excommunicate the churches of Irenaeus’s native Asia Minor for celebrating Pascha (later called Easter) on 14 Nisan, rather than the following Sunday, as they did in Rome. Irenaeus wrote irenically to Victor and the bishops of the Asian churches, urging them that on such secondary matters both parties should be free to celebrate according to their own tradition. It was an important little incident, for it showed that, despite all Irenaeus’s emphasis on unity in the apostolic tradition, he did not countenance unconditional submission to the bishop of Rome, and could allow for different practices in the church.

Irenaeus wrote a number of works of theology; today, though, apart from a number of fragments from his writings, we have only two complete works of his: Detection and Refutation of What Is Falsely Called “Knowledge,” usually known simply as Against Heresies, and his much shorter Demonstration of the Apostolic Preaching. In these works we see the first serious attempts to formulate Christian doctrine into a coherent structure. Irenaeus is thus a key architect of Christian thought. As such it is unsurprising that his influence spread so rapidly and so far (a fragment of Against Heresies, dating from when Irenaeus was still alive, has been found at Oxyrhynchus in Egypt, at the other side of the known world from where he wrote the work). We actually have no idea when or how Irenaeus died, though later tradition has it that he was martyred on June 28, 202.

​​Against Heresies

By the middle of the second century, a collection of sects we now lump together and call Gnosticism had infected much of the church with various odd mutations of Oriental and Greek philosophies. One branch in particular seemed to be thriving: Valentinianism. Its leading light, Valentinus, once expected to become the next bishop of Rome, was an influential, gifted, and persuasive theologian who managed to draw a number of disciples to his peculiar beliefs. Quite a number in the church in Lyons had been won over. Irenaeus saw this Gnosticism as a manyheaded monster, threatening his flock. And, a pastor at heart, through his great five-volume work Against Heresies, he set out to protect the Christians, convert the Gnostics from their error, and bring them to saving knowledge and, ultimately, kill the monster. Certainly, Against Heresies struck Gnosticism a mortal blow.3

Irenaeus’s Against Heresies is also available online (at http://www and in the Ante-Nicene Fathers series in the same translation (also vol. 1). It is well worth a few hours’ time, though a warning to the reader: unless you are very keen to learn about second-century Gnosticism, skip the first two books! For those who just want a taste of Irenaeus, John Behr’s translation of The Demonstration of the Apostolic Preaching (Crestwood, NY: SVS, 1997) is excellent, and it comes with very helpful notes and an introduction—highly recommended. For anyone interested in following up Irenaeus’s main themes of incarnation and recapitulation, one outstanding introduction is worth mentioning: Gustaf Wingren, Man and the Incarnation: A Study in the Biblical Theology of Irenaeus (Edinburgh: Oliver & Boyd, 1959).


  1. Irenaeus, Against Heresies 1.preface.3.
  2. Emil Brunner, The Mediator: A Study of the Central Doctrine of the Christian Faith, trans. O. Wyon (London: Lutterworth, 1934), 262.
  3. However, the fact that Gnosticism never quite died out is one reason why Irenaeus remains relevant today. Irenaeus believed that Valentinus had managed to come up with the definitive heresy that summed up and encapsulated all heresies. If there is any truth to that, it should be no surprise that we live today in a culture increasingly fed on a diet of rewarmed Gnosticism (witness the essential Gnostic themes of Dan Brown’s The Da Vinci Code and Philip Pullman’s His Dark Materials trilogy).

This article is adapted from Theologians You Should Know: An Introduction: From the Apostolic Fathers to the 21st Century by Michael Reeves.

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