In A.D. 177, the people of Lyon (the capital of Gaul, today’s France) went after the city’s Christians. It had been a trying time for the people of Southern Gaul, who had been suffering from frequent enemy raids and a deadly plague. To those who hadn’t embraced Christ, the Christians’ refusal to worship pagan deities was a credible explanation to the gods’ fury. Long existing prejudices escalated into a full-scale riot. Residents assaulted Christians, dragging them to the public square. City authorities evaded responsibility, instead throwing Christians in prison and submitting the matter to the governor.

Eventually, the Christians were condemned for repudiating the authorities’ demands. Some were cruelly executed in a public arena, while others, like Pothinus, the bishop of Lyon, died in prison. In the wake of this nightmare, Irenaeus, who was likely traveling when the tragedy occurred, returned to pick up the pieces. As Pothinus’s successor, he was faced with all the questions of a tragic aftermath: how to care for widows and orphans, console the suffering, encourage the defectors, relieve fears, and promote unity.

A Missionary to Gaul

By the time Irenaeus moved to Gaul, Christianity was growing rapidly. Historians estimate that, by the end of the first century, the Christians in the Roman Empire were fewer than 10,000. By A.D. 150, they had grown to about 40,000, and by the end of the second century, they were more than 200,000. They were mostly spread around the Mediterranean Sea, but some of them ventured beyond the boundaries of the empire. The persecution was sporadic, mostly instigated by the common people.

Early Christians were organized in churches and united by common beliefs, which were expressed in short official statements known as “Rule of Faith” (an early form of the Apostles’ Creed). Their customs and traditions, however, were very different and changed from place to place. No one knows for sure how long the Christian communities had been in Gaul when Irenaeus arrived there. It appears that they were already there around the middle of the second century—mostly immigrants from Asia Minor.

Very little is known about Irenaeus’s life. Even the year of his birth has been disputed. He might have been born around A.D. 130 or 140 in today’s Turkey, where he studied (specifically in Smyrna, today’s Izmir) under Bishop Polycarp. As a direct disciple of the apostle John, Polycarp echoed John’s warnings against false teachers. Later in life, Irenaeus still remembered Polycarp’s cry, “O good God, for what times hast Thou reserved me, that I should endure these things?”


Gnosticism (from the word gnosis, meaning knowledge) is a term of convenience used by later historians. The various tendencies under this umbrella had one thing in common: a desire for higher knowledge. As such, they were already mentioned in New Testament warnings by Paul (especially in the Epistle to the Colossians), John (in his first epistle), and Jude.

Most likely, Irenaeus encountered Gnostics when he traveled to Rome, which at that time had a population of over a million people from all over the known world. He was particularly acquainted with a group known as Valentinians, who were part of the widespread phenomena we today refer to as Gnosticism. Irenaeus took time to study Gnostic writings and to talk to Gnostics in person. His conclusions, however, were firm and unequivocal: These people were wolves in sheep’s clothing, and their statements were “absurd and inconsistent with the truth.”

At the encouragement of a friend, Irenaeus wrote his reflections in a series of five books, which he titled The Refutation and Overthrowal of Knowledge Falsely So-Called (today known as Against Heresies), a project he continued for a number of years, between A.D. 175 and 189.

He might have started writing before moving to southeastern Gaul, where he served as presbyter (or bishop, since the two words were used interchangeably). He mostly operated in Vienne and Lyon, two cities about 20 miles from each other. It was a prosperous region, particularly important as a center of trade and Celtic religious rites. Every year, Lyon hosted a meeting of the 60 tribes from the area and a popular festival in honor of the sun god Lugh (equivalent of the Roman Mercury).

Bringing Truth to a Persecuted Church

It was just before this festival, in 177, that the Lyonnaise attacked the Christians. Irenaeus was probably in Rome, where he had been sent to carry a letter to Bishop Eleutherius and discuss the controversial teachings of Montanus in Asia Minor. The authors of the letter commended Irenaeus as being “zealous for the covenant of Christ.”

When he returned, the questions facing Irenaeus were urgent and complex. While the faith of some survivors had been strengthened through the persecution, many others were wearied by the struggle. The taunts of their fellow citizens questioning where their God “was” were still fresh.

Beyond the threat of violence from those who still followed traditional Roman beliefs, Irenaeus had to address heresy within the church. In the wake of the tragedy, the temptation to Christians to fall into the Gnostics’ teachings was great. Gnosticism, in its various forms, had encouraged people to look for higher knowledge and a more sophisticated understanding of Christian belief than what the apostles and the local churches could offer. While adherents organized themselves in separate communities, they often gained a hearing within the churches.

The Gnostic message had a wide appeal. First of all, the prospect of obtaining a higher, secret knowledge is always tempting. Second, Gnosticism provided a plausible explanation of the problem of evil as the result of the impulsive and vindictive whims of an inferior god, and this struggle between two deities made sense. Third, the Gnostics’ contempt for the material world allowed many of them to consider pagan ceremonies inconsequential. They could in good conscience accept the demands of the Roman government and escape persecution. In addition, their message sounded biblical enough to attract those who didn’t have time to submit their claims to serious examination.

For Irenaeus, the main problem with Gnosticism was that it was not historical Christianity. The Gnostics were not interested in the historical Jesus and didn’t see the Bible as a unified story of redemption. To them, salvation was obtained through enlightenment and was only available to a chosen few. Their writings were earnest and poetic but quite different in scope and spirit from the canonical gospels.

Since the biblical narrative was not important to them, they could cast doubts on some of the basic tenets of the Christian faith. For example, some taught that the man on the cross was not the same as the miracle-working Christ, because it was not fit for Christ to suffer. This was problematic on both soteriological and practical levels. To persecuted Christians, it would have raised the question of why Christ asked his followers to accept abuses to the point of death when he himself escaped all suffering.

Besides, while most Gnostics were sincerely convinced of possessing the truth, a few used the appeal of higher knowledge as a means of exploitation. A Gnostic named Marcus was especially crafty around Lyon, performing tricks with water and wine to mimic Christ’s miracles and amaze his followers. He targeted wealthy women, urging them to give messages from God by saying the first thing that came into their minds. When they did, he proclaimed them prophetesses, accepting their valuable gifts and sexual favors as tokens of their gratitude. Only a few women recognized the deception and returned to the church.

These and many other pressing problems made Irenaeus’s work against the Gnostics particularly pastoral. He hoped to help not only those who were attracted by their message but the Gnostics themselves, because he loved them “better than they seem to love themselves.”

Answering the Gnostics

The Gnostics’ teachings were not an easy study. Unlike the apostles’ writings, which the Gnostics scorned as overly simple, these included complicated explanations. Some believed that the world was created by a dual god who emitted another single or dual being, forming a unit that generated a succession of Aeons or spiritual beings or powers who performed different functions in the universe. Some Gnostics gave personal, subjective names to these beings, often revealed through an elaborated code of numbers or letters.

Navigating and explaining the multiple variations of this system was enough to weary the toughest mind. Erasmus of Rotterdam, who published the first printed edition of Against Heresies in 1526, commented that Irenaeus had a patientis stomachi to digest their doctrines. Irenaeus would have agreed, as he ended his survey with the typical cries of Greek tragedies, Iu, Iu! Pheu, Pheu!

Irenaeus used satire to highlight the incongruities he found in the Gnostics’ universe. If the names of these Aeons were arbitrary, why not call one of them Gourd and his coexisting power Utter Emptiness? “This Gourd and Emptiness, since they are one, produced (and yet did not simply produce, so as to be apart from themselves) a fruit, everywhere visible, eatable, and delicious, which fruit-language calls a Cucumber,” Irenaeus mocked. “Along with this Cucumber exists a power of the same essence, which again I call a Melon.”

Irenaeus’s main responses came from logic and Scriptures. He employed logic to point out that two contrasting gods, being inevitably imperfect and limited, can hardly be called gods. His abundant use of Scriptures (629 citations from both the Old Testament and 1,065 from the New) is impressive and unique among second-century writers, who relied largely on logic or—as in the case of Justin Martyr—on primarily Old Testament writings. It was for Irenaeus a careful and deliberate choice, in order to confirm the apostolic truth the Gnostics refuted. His inclusion of New Testament Scriptures is particularly useful to historians as a proof that many of the books that compose this part of the Bible were already authoritative at that time.

The Unity of Scriptures

Irenaeus’s desire to answer the Gnostic contrast between a capricious and malevolent creator of an evil and defected world and the good and loving God of the New Testament produced a most vigorous and lucid explanation of the unity of Scriptures, culminating in the doctrine we call “recapitulation.”

Irenaeus reminds his readers of the biblical narrative, where there is only one God, who is perfect, omnipotent, uncreated, and the only source of every good thing. This God created the world good and has continued to preserve it through history in spite of the rebellion of the first Adam. In the fullness of time, God sent his only son as a second Adam to take on human flesh (the same flesh the Gnostics despised) and accomplish what the first Adam failed to do.

This reminder was also important on a soteriological level. By rejecting anything physical, the Gnostics denied Christ’s incarnation and his effective work of salvation, reducing him to the role of an enlightened being sent to open the eyes of spiritual men to a secret knowledge. Also, by picking and choosing Scriptures, they obscured the unity of the biblical story of salvation through Jesus Christ, “who came [so that], taking to Himself the pre-eminence, as well as constituting Himself Head of the Church, He might draw all things to Himself at the proper time.”

A Passionate Faith

Throughout Irenaeus’s writings, it’s clear that his doctrines are not sterile notions. He writes enthusiastically and passionately, communicating his excitement for the beauty of God’s person, truth, and works, which include the created world and the gospel. His heart soars as he challenges the Gnostics to come even slightly close to God’s incomparable creation: “What heavens have they established? What earth have they founded? What stars have they called into existence? Or what lights of heaven have they caused to shine? Within what circles, moreover, have they confined them? Or, what rains, or frosts, or snows, each suited to the season, and to every special climate, have they brought upon the earth?”

This excitement over who God is and what he has done in Christ stands, for Irenaeus, as the basis of the Christian’s way of life—a life that is marked by grateful obedience, love, and exuberance. The motivation has changed. Christian giving, for example, is “made, not by slaves, but by freemen.” Irenaeus saw martyrdom as the culmination of the Christian path and a chance to demonstrate what he considered the highest form of love: love for our enemies.

Irenaeus’s Relevance

Some believe that Irenaeus died as a martyr in 202 or 203, during the persecution unleashed by Emperor Septimius Severus. There is no solid proof of this. Jerome mentions it in his commentary on Isaiah, written in 410, but not in his 392 biographical work De Viris Illustribus. In any case, the last writing we have from Irenaeus is from 190, so the date, if not the mode of Irenaeus’s death, might be fairly accurate.

His legacy, however, lived on. From a purely historical point of view, Against Heresies is still considered the best analysis of Gnosticism from an eyewitness.

Erasmus, whose work many argue paved the way for the Protestant Reformation, identified so strongly with the theologian’s passion for biblical truth that he called him “my Irenaeus.” Erasmus lamented that Irenaeus’s priscum vigorem (early vigor) was sorely absent in the 16th-century church, together with the bishop’s love for peace.

The name Irenaeus means, in fact, “peacemaker,” and the second-century bishop had several occasions to live up to his name. One of these occurred in A.D. 190, when Irenaeus encouraged Victor, bishop of Rome, to accept the different dating of Easter used by the Christians from Asia Minor who lived in Rome, instead of excommunicating them as Victor had threatened to do. As strict as Irenaeus was in matters of essential doctrine, he stood for tolerance in minor issues.

Erasmus might have referred to this occasion when, at the end of his introduction to his edition of Against Heresies, he prayed God would raise some new Irenaei to bring peace to his troubled times. His prayer is still as relevant today.

Simonetta Carr is the author of the award-winning series Christian Biographies for Young Readers, published by Reformation Heritage Books. She also writes a regular column, “Cloud of Witnesses,” for the Alliance of Confessing Evangelicals.