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St. Irenaeus of Lyon: Getting to know the new Doctor of the Church

Why has Pope Francis chosen Irenaeus to be our latest Doctor, and why will he name him Doctor of Unity? To answer these questions, we must look at this life and accomplishments.

A stained-glass window by Lucien Bégule depicting St. Irenaeus at the Church of St, Irenaeus in Lyon, France. / Gérald Gambier via Wikimedia (Public Domain).

On 7th October 2021, Pope Francis announced that he planned to name St. Irenaeus of Lyon as the 37th Doctor of the Church, giving him the title “Doctor of Unity”. And this past Friday, he declared St. Irenaeus the 37th Doctor of the Church, with the title “Doctor Unitatis” (“Doctor of Unity”).

“May the doctrine of such a great Master encourage more and more the path of all the Lord’s disciples towards full communion,” Pope Francis stated in his January 21st decree.

The tradition of calling certain Christians doctors (teachers) of the Church, goes back to the Middle Ages, when theologians of that time recognized four Fathers of the Church, Sts. Gregory the Great, Ambrose, Augustine of Hippo, and Jerome, as being preeminent teachers of the faith.

In the Eastern Church, three Church Fathers, Sts. John Chrysostom, Basil the Great, and Gregory of Nazianzus (also called Gregory the Theologian), came to be recognized as the greatest teachers of the faith. In the West, these three also came to be venerated as teachers of the faith and, to even up the numbers, a fourth eastern Father was added, St. Athanasius, making a total of four eastern Doctors and four western Doctors.

From 1567, more Doctors were named, beginning with St. Thomas Aquinas. They include people who were bishops, priests, deacons, monks, friars, nuns, and one layperson.i Some, like Aquinas, were academic theologians. Others, like St. John of the Cross and St. Catherine of Siena, were mystics. As yet, no married person has been named a Doctor. To be named a Doctor a person must be eminent in learning and display a marked degree of holiness.

Why has Pope Francis chosen Irenaeus to be our latest Doctor, and why will he name him Doctor of Unity? To answer these questions, we must look at this life and accomplishments.

Irenaeus is believed to have been born in Smyrna in modern day Turkey around 135 AD. He could be regarded as a third generation Christian. As a young man, he was taught by Bishop St. Polycarp of Smyrna, who in turn had been a disciple of St. John the Evangelist. By 177 AD he had moved to Gaul, contemporary France, being recorded as a priest in the church at Lugdunum (Lyons). This was a large and important Roman city on the river Rhône.

In that same year he was sent with a letter from the persecuted community in Lyons to Pope Eleutherius. This mission may have saved his life for, in his absence, the 90-year-old Bishop Pontinus died from ill-treatment in prison, and at least 47 other Christians were martyred. On his return Irenaeus was appointed as the second bishop of Lyon. He devoted himself to this ministry for the next 25 years. He is believed to have been martyred around 202 AD.

Two works of Irenaeus survive. One is called The Demonstration of the Apostolic Teaching. It was discovered only in 1904, in an Armenian translation. It seems to have been written to instruct recent converts to Christianity, and it has been called the oldest catechism of Christian doctrine. The other and far more famous work is The Detection and Overthrow of the False Gnosis, usually known as Adversus Haereses (Against Heresies). Originally written in Greek, complete copies have survived only in Latin, although the last two of its five books have also survived in Armenian.

The main target of this work was a group of people called Gnostics. This term comes from the Greek term for knowledge. English words like “agnostic,” “ignorant,” “diagnosis,” and “prognosis” are derived from it. The Gnostics were people who claimed to be Christians, but Christians who possessed a special, secret knowledge.

Gnosticism was a mixture of Christian, pre-Christian, and contemporary pagan beliefs. It was also diverse; there were many Gnostic variants. It was esoteric, offering a hidden knowledge obtainable only by the few. It claimed to see behind the “symbolism” of the doctrines believed by ordinary Christians, like the resurrection of Jesus. According to it, we are saved by coming to the realization that spiritually, we are already divine. Creation takes place through an intermediary, a “demiurge,” and subsequent emanations. Evil comes from a demiurge who thought he was the original God. This is an attempt to explain suffering and corruption; the spiritual has been imprisoned in the material. Gnosticism was essentially dualistic. Spirit is good. Matter is bad. Both good and evil have divine sources.

Rather than appeal much to Sacred Scripture, the Gnostics wrote their own Scriptures, for example, the Gospel of Thomas, the Gospel of Philip, the Gospel of Judas, and many others. Many of these writings were discovered in 1945 in a monastic library in an Egyptian town called Nag Hammadi.

In these writings, Jesus is sometimes portrayed in a docetic manner, as not truly being in the flesh, but only appearing to be so (from dokeis meaning “apparition”). For others, he is an embodiment of the a divine being who became incarnate to bring gnosis to the earth, but he does not die for us, nor rise from the dead. For others, he is not God come in the flesh, but a human being who attained enlightenment through gnosis and taught his disciples to do the same. If Gnosticism were true, then Jesus was not truly God. Nor was he truly one of us, truly human, and he could not offer his humanity perfectly to the Father.

Rather than give my own poor account of the significance of his defense of the Catholic faith, I would like to quote from Pope Benedict XVI’s assessment of it, given at a General Audience on 28th March, 2007.

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.

For Irenaeus, the great principle that founds the faith we believe is the Apostolic Tradition. This Tradition is “public,” not secret. This “tradition [is] passed down by the Apostles and the faith proclaimed to men,” coming “down to us through the succession of Bishops”ii.

Unlike the teaching of the Gnostics, who gave many different versions of their beliefs, this Tradition is “one”.

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.iii

Finally, this teaching is upheld by the Holy Spirit. This teaching,

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.iv

Given the importance of St. Irenaeus, the question about his being named a Doctor of the Church should be more along the lines of: “Why has it taken so long”? Yet why does Pope Francis wish to name him Doctor of Unity now?

The Pope made his original announcement at an audience with the St. Irenaeus Orthodox-Catholic Joint Working Group. This group is not an “official” one, but an unofficial initiative of the Johann Mohler Institute for Ecumenism. It is comprised of 13 orthodox theologians from various Orthodox Churches, and 13 Catholic theologians.

The group chose St. Irenaeus as their patron because he is revered as a Father of the Church by both Eastern and Western Churches. He was a Greek speaking easterner who ministered as a bishop in the West. We have even seen above that his work was known as far away from Gaul as Armenia in the Caucasus Mountains, the first country to adopt Christianity as its official religion.

Furthermore, as the Pope pointed out to the group, the name Irenaeus is derived from the Greek word eirenaios, which comes from the Greek word for “peace” (we derive the English word “irenic” from it). It is for this reason that the Pope has named St. Irenaeus Doctor Unitatis, someone who can be a model of that unity desired by all who love the broken Body of Christ.

(A version of this article appeared as “Irenaeus: Doctor of the Church,” in the Catholic Weekly, January 2, 2022, 10-11.)


i St. Catherine of Siena was a Dominican tertiary.

ii St. Irenaeus, Adversus Haereses, 3, 3, 3-4.

iii Ibid., 1, 10, 1-2.

iv Ibid., 3, 24, 1.

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About Peter John McGregor 3 Articles
Peter John McGregor is a lecturer in dogmatic theology and spirituality at the Catholic Institute of Sydney, Australia.


  1. “No married person has been named a Doctor of the Church.” Really? Is that a thing? Do we care? We are looking for spiritual leadership and defense of the church and our doctrine here. This is a not a diversity woke session,nor are we looking to go down the recent academic tradition of a quota system, I hope. On the other hand, lets see what the now schismatic Germans say.

    • Dear LJ, I was not making a woke point, or making a judgement, just stating a fact. I would not classify myself as being, in an sense, woke. Hopefully, one day a married person will be named a doctor. Yours in Christ, Peter McGregor

3 Trackbacks / Pingbacks

  1. St. Irenaeus of Lyon: Getting to know the new Doctor of the Church – Via Nova Media
  2. St. Irenaeus of Lyon: Getting to know the new Doctor of the Church – Catholic World Report – The Old Roman
  3. St. Irenaeus of Lyon: Getting to know the new Doctor of the Church – Columbus Catholic Corner

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