Irenaeus
Second-century Greek bishop, defender of orthodoxy against Gnosticism, and author of Against Heresies.
Irenaeus was a second-century Greek bishop who helped shape Christian communities in what is now southern France and became a key figure in early Christian theology. He is best known for pushing back against Gnostic readings of Christian scripture and defending what he saw as orthodox belief. Born in Smyrna (modern-day İzmir, Turkey), he grew up in a Christian family and heard Polycarp preach—Polycarp was said to have been a listener of John the Evangelist. Around 180, as bishop of Lugdunum (today’s Lyon), Irenaeus wrote *Against Heresies*, a work aimed at refuting Gnostic teachings, especially those of Valentinus. To counter Gnostic claims of secret knowledge, he laid out three foundations of orthodoxy: the scriptures, the tradition passed down from the apostles, and the teachings of the apostles’ successors. He is the earliest surviving writer to treat all four of the now-canonical gospels as essential.
Irenaeus was a priest in Lyon during a persecution under Emperor Marcus Aurelius. In 177, the clergy of Lyon, many imprisoned for their faith, sent him to Rome with a letter to Pope Eleutherius about the heresy of Montanism. While he was in Rome, the persecution in Lyon occurred. After returning, he succeeded the martyred Saint Pothinus as the city’s second bishop. During a subsequent period of religious peace, he balanced pastoral duties with missionary work, though details are sparse. Most of his writings targeted Gnosticism. He mentions encountering Gnostic texts and conversing with Gnostics, possibly in Anatolia or Rome, and notes that followers of “Marcus the Magician” were active in the Rhone valley.
Little is known of his later years as bishop. The last recorded action, from Eusebius 150 years later, is that around 190 or 191, Irenaeus urged Pope Victor I not to excommunicate Anatolian Christian communities that kept the Quartodeciman practice for Easter. His death date is unknown, likely at the end of the second or start of the third century. He is considered a martyr by the Catholic Church and some Orthodox traditions. He was buried under the Church of Saint John in Lyon, later renamed St. Irenaeus, which was destroyed by Huguenots in 1562. Several relics claimed to be his exist in Lyon churches; carbon-14 dating showed two crania from different churches were medieval, but a heelbone in Lyon Cathedral dates to the right period.
Irenaeus is venerated as a saint in the Catholic, Anglican, Lutheran, Eastern Orthodox, Oriental Orthodox, and Assyrian Church of the East traditions. The Latin Catholic Church marks his feast on 28 June; Pope Francis named him the 37th Doctor of the Church on 21 January 2022, with the title *Doctor unitatis* (“Doctor of Unity”). The Eastern Orthodox Church celebrates him on 23 August. Lutheran, Church of England, and Episcopal calendars also honor him on 28 June.
His most important surviving work is *Against Heresies* (Latin: *Adversus haereses*), written around 180. Book I describes Valentinian Gnostics and their predecessors, tracing them back to Simon Magus. Book II argues that Valentinianism has no doctrinal merit. Book III uses the Gospels to show these doctrines are false. Book IV focuses on Jesus’ sayings and stresses the unity of the Old Testament and the Gospel. Book V covers more of Jesus’ sayings and the letters of Paul. Irenaeus wrote that truth should be sought from the Church, where the apostles placed all that pertains to truth, calling it “the door of life.” He also said Christ came for all people from the beginning who feared and loved God and lived justly, not only those after Tiberius Caesar.
- born
- Some time before Polycarp's death circa 155 AD, Smyrna (now İzmir, Turkey)
- died
- End of the second or beginning of the third century
- field
- Christian theology, bishopric, anti-Gnostic polemics
- nationality
- Greek
- known_for
- Writing *Against Heresies*, opposing Gnosticism, earliest surviving witness to regard all four canonical gospels as essential
Lore & Background
Irenaeus was a Greek from Polycarp's hometown of Smyrna in Anatolia, now İzmir, Turkey, born some time before Polycarp's death circa 155 AD. Unlike many of his contemporaries, he was brought up in a Christian family rather than converting as an adult. During a local persecution of Christians around Lyon during the reign of Marcus Aurelius, the Roman emperor from 161 to 180, Irenaeus was a priest of the Church of Lyon. The clergy of that city, many of whom were suffering imprisonment for the faith, sent him to Rome in 177 with a letter to Pope Eleutherius concerning the heresy of Montanism. While Irenaeus was in Rome, the Lyon persecution took place. Returning to Gaul, Irenaeus succeeded the martyr Saint Pothinus and became the second bishop of Lyon. During the religious peace which followed the Lyon persecution, the new bishop divided his activities between the duties of a pastor and of a missionary. Little is known about the career of Irenaeus after he became bishop. The last action reported of him (by Eusebius, 150 years later) is that in 190 or 191, he exerted influence on Pope Victor I not to excommunicate the Christian communities of Anatolia which persevered in the practice of the Quartodeciman celebration of Easter. Nothing is known of the date of his death, which must have occurred at the end of the second or the beginning of the third century. He is regarded as a martyr by the Catholic Church and by some within the Orthodox Church. He was buried under the Church of Saint John in Lyon, which was later renamed St Irenaeus in his honour. The church was devastated in 1562 by the Huguenots. Several relics supposedly of Irenaeus are held in various churches in Lyon. Two crania from different churches were dated by carbon-14 to the Middle Ages, but a piece of heelbone kept in the Lyon Cathedral is from the right time period.
Reader's Guide
Irenaeus is venerated as a saint in the Catholic Church, Anglican Church, Lutheran Churches, the Eastern Orthodox Church, the Oriental Orthodox Churches, and the Assyrian Church of the East. He was declared a Doctor of the Church in the Catholic Church by Pope Francis in 2022. The Latin Catholic Church celebrates Irenaeus' memorial on 28 June. Pope Francis also conferred upon Irenaeus the supplementary title Doctor unitatis ('Doctor of Unity'). The Eastern Orthodox Church celebrates Irenaeus on 23 August. Lutheran Churches honor Irenaeus on their calendar of saints on 28 June. Irenaeus is honored in the Church of England and in the Episcopal Church on 28 June. Irenaeus wrote a number of books, but the most important that survives is the Against Heresies (Adversus haereses), written around 180. He also wrote The Demonstration of the Apostolic Preaching (also known as Proof of the Apostolic Preaching), an Armenian copy of which was discovered in 1904. Eusebius attests to other works by Irenaeus, today lost, including On the Ogdoad, an untitled letter to Blastus regarding schism, On the Subject of Knowledge, On the Monarchy or How God is not the Cause of Evil, On Easter. Irenaeus exercised wide influence on the generation which followed. Both Hippolytus and Tertullian freely drew on his writings. However, none of his works aside from Against Heresies and The Demonstration of the Apostolic Preaching survive today. Even though no complete version of Against Heresies in its original Greek exists, we possess the full ancient Latin version, probably of the third century, as well as thirty-three fragments of a Syrian version and a complete Armenian version of books 4 and 5.
Did You Know?
- Irenaeus is the earliest surviving witness to regard all four of the now-canonical gospels as essential.
- Until the discovery of the Library of Nag Hammadi in 1945, Against Heresies was the best-surviving description of Gnosticism.
- The general consensus among modern scholars is that Irenaeus was fairly accurate in his transmission of gnostic beliefs.
- Irenaeus wrote: 'One should not seek among others the truth that can be easily gotten from the Church. For in her, as in a rich treasury, the apostles have placed all that pertains to truth, so that everyone can drink th
Notable Quotes (Wikiquote)
"Book 3, Chapter 3. From Readings in World Christian History (2013), pp. 58-99." — Irenaeus "It is not necessary to seek truth among others which it is easy to obtain from the Church." — Irenaeus "Book 3, Chapter 4. From Readings in World Christian History (2013), pp. 58-99." — Irenaeus "Book 3, Chapter 22, paragraph 4. From Philipp Schaff, Irenaeus Against Heresies, in The Writings of the Fathers Down to A.D. 325. ante-nicene Fathers, Volume 1 - The Apostolic Fathers, Justin Martyr, Iraneus,p. 455." — Irenaeus
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