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Core Christianity: Tough Questions Answered

Defender of Truth: Meet Irenaeus

by Andrew Menkis posted November 28, 2022

This article is part of our series, “Cloud of Witnesses: Stories from the Church.” Read more from the series here.

Tertius listened closely and wrote quickly, eager to ensure every word was captured. He was a scribe, working for one of the influential leaders in a new religious sect called “the Way.”[1] This new religion was spreading rapidly around the Roman empire. Tertius was recording the letter of a well-educated Jew named Paul, who had converted unexpectedly to this sect after strongly opposing it. Paul’s letter was addressed to fellow converts living in the epicenter of civilization, the city of Rome. As he came to the end of his letter, he delivered a passionate warning against false teachers:

“I appeal to you, brothers, to watch out for those who cause divisions and create obstacles contrary to the doctrine that you have been taught; avoid them.”[2]

From its beginning, followers of the Way—a movement we now call Christianity—faced threats. Some of these came from without, such as persecution by the Roman government. Other threats came from within. In this warning, Paul speaks of the danger of false teachers within the church who create division and contradict the apostolic message, which had been delivered to the first leaders in the Christian movement by the founder himself, Jesus of Nazareth. This danger did not and has not gone away. Early in the history of the church it became necessary for Christians to combat false teachers and false beliefs, exposing their errors and affirming the true doctrine which had been handed down from Jesus through the apostles. Those who engage in this work are called apologists. This title comes from an older meaning of the term “apologize”: to give a defense. One of the earliest Christian apologists was a man named Irenaeus.

Irenaeus of Lyons

Biographical details about Irenaeus are sparse and sporadic. He was born to Greek parents sometime between 115 and 142 A.D., most likely in Asia Minor. Perhaps his parents were Christians, because he tells us that as a young boy he saw the famous bishop of Smyrna, Polycarp. In any case, he himself was a Christian. At some point in his life, he moved to Gaul to serve the church. We know for certain that when the Bishop of Lyons was martyred, Irenaeus took his place.[3] This all would have taken place a little before 180 B.C. During these years, Irenaeus began to do the work of an apologist by researching and writing responses to false teachers and beliefs.

Main Opponents: Marcion & Valentinus

The church faced a variety of opponents and false teachings during the second century. Irenaeus addressed many of these challenges but focused primarily on the two of the most prominent false teachers: Marcion and Valentinus. Marcion taught that the God of the Old Testament was a different God from that of the New Testament. The God of the Old Testament was the creator, a violent and vindictive God. The God of the New Testament was the loving Father of Jesus Christ. Jesus was the Son of God, but Marcion denied that he became human.[4]

Valentinus was a gnostic theologian. Gnosticism gets its name from the Greek word for knowledge, gnosis. Valentinus and his followers asserted that they possessed secret gnosis. It was information not found in the widely accepted and read accounts of the life and ministry of Jesus Christ. In other words, Valentinus claimed to have teachings not found in Matthew, Mark, Luke, and John. These teachings came in the form of unwritten traditions as well as written Gospels in addition to the four typically accepted. While Valentinus was not the only gnostic to make such claims, he was perhaps the most influential one of the second century.

What was Irenaeus to do in the face of such strong and influential opponents to the apostolic faith? He decided to write a five-part series of responses and rebuttals. He took his time to research his opponents’ views and understand them exhaustively so that he could respond knowledgeably and definitively. Today these are often published together in one edition under the title, Against Heresies.

Response to Marcion

In response to Marcion’s claim that a complete and radical distinction must be made between the God of the Old and the God of the New Testament, Irenaeus attempted to prove that there is in fact one God of the Bible. He gave two main reasons in support of his claim: First, he argued the fulfillment of Old Testament prophecies by Christ in the New Testament show there is one God. He wrote,

Read with earnest care that Gospel which has been conveyed to us by the apostles, and read with earnest care the prophets, and you will find that the whole conduct, and all the doctrine, and all the sufferings of our Lord, were predicted through them.[5]

The unity of the message of the Old and New Testaments points to one author, a single God who foretold the coming of Christ and sent him.

The second argument that runs throughout Irenaeus’ writing has to do with the relationship between Adam and Jesus. He argued that there are parallels between Adam and Christ. The parallels show there is one God, with one plan of salvation, who inspired the entire Bible. As he read the Old and New Testament books together, Irenaeus saw that Jesus was a “recapitulation,” or “do-over” of Adam.[6] For example, Irenaeus saw a parallel between the temptation of Adam and of Christ. In Eden, the serpent tempted Adam with fruit. When Satan tempted Jesus in the desert, he again used food, tempting Jesus to cease fasting and make bread out of stones. Irenaeus wrote,

For as at the beginning it was by means of food that [the enemy] persuaded man . . . to transgress God’s commandments, so in the end he did not succeed in persuading Him that was hungered to take that food which proceeded from God.[7]

Jesus did what Adam could not, he resisted Satan’s temptation. Irenaeus pointed out that Jesus’s response to Satan, “Man cannot live on bread alone,” acknowledges that he, like Adam, truly is a human being at the same time as being truly divine.[8] Jesus is, as Paul puts it, the “last Adam” (1 Cor. 15:45). By highlighting the parallels between Adam and Christ, the unity between the story and characters of the Old and New Testament is demonstrated. There is one God of the Old and New Testament: a just and loving Father who has one majestic plan to save sinners through the second Adam, his beloved Son, Jesus Christ, by the power of the Holy Spirit.  

Response to Valentinus

It’s worth diving into Irenaeus’s response to Valentinus. Theologian and historian Henry Chadwick contends that “Irenaeus’s[1]  treatment of the Valentian theology was the most original and independent part of his work.”[9] This is because, in his response to the Valentinians, Irenaeus made significant contributions to the formation of the New Testament canon, established the chain of information about Jesus from the apostles to his own time, and cast a vision for the task of a theologian.

The Canon

The Valentinians claimed to have sources of religious knowledge that the church did not possess. These included secret traditions passed down from the apostles and books called gnostic Gospels [2] . In light of these claims, Irenaeus saw that it was necessary for the church to establish a formal list of books recognized as Scripture. A list like this is called a canon. Canonical books are those recognized by the church as having authority to tell Christians what truths they should believe and how they can please God with their lives. During Irenaeus’s life, the Old Testament canon had been officially established, but the New Testament canon had not.

In order to respond to Valentinus, Irenaeus saw that he would have to mount an argument for a canon and give reasons to exclude the gnostic teachings (whether oral traditions or written Gospels). The list of books that Irenaeus treats as Scripture almost perfectly matches the canon the church would officially adopt. In particular, he was very adamant that there are only four Gospels.[10] He quoted from almost every New Testament book with the exceptions of 3 John, James, and 2 Peter.[11] He excluded any additional gnostic Gospels, and significantly, rejected any secret apostolic teaching. Irenaeus argued that the books of the New Testament, written by the apostles, trumped any claim to a secret oral tradition, especially if the supposed traditions contradicted the written canonical Scriptures.

The Apostolic Faith

This leads directly into Irenaeus’s second argument against the Valentinians. He contended that the idea of secret apostolic teachings is ludicrous. His argument is simple. If the apostles had such a secret teaching, they would have passed it on to important church leaders. These special church leaders would, in turn, pass the tradition on to their successors. All that needs to be done then is to go back to the apostles, trace the succession of church leaders after them, and analyze the message they taught: was it the message of the Valentinians or that of the canonical Scriptures?

To make his point, Irenaeus used the church in Rome as an example. From Peter and Paul, the two apostles of Rome, he traced the succession of leaders in the church to his present day when Eleutherius was head of the church in Rome. This unbroken line of apostolic succession preserved a continuous and apostolic message that was in contradiction to gnostic teachings. In Irenaeus’s own words, “And this is most abundant proof that there is one and the same vivifying faith, which has been preserved in the Church from the apostles until now, and handed down in truth.”[12] Upon examination, the Valentinian’s supposed apostolic teaching did not have any evidence that they were any older than Valentinus himself.

The Discipline of Theology

There is a practical application to all these arguments against Valentinus. Irenaeus shows us that the task of theology is preservation, proclamation, and defense of the Scriptures. A theologian is not in the business of inventing their own original ideas. A true theologian may find some unique insights into Scripture or find a way to explain something with more precision or clarity, but they should never move beyond the apostolic message which is recorded for us definitively in the New Testament.

Irenaeus’s Legacy Today

The church today—like the church in Rome during the apostle Paul’s life or the church in Lyons during Irenaeus’s life—faces false teachers. The church still needs theologians and apologists to defend the apostolic truth against false teachings. Is God calling you to defend the faith once delivered? May the Lord raise up apologists and theologians in the mold of Irenaeus who have the gifts and courage to defend the truth of the gospel!

[1] Acts 9:2, 24:14

[2] Romans 16:17

[3] See Eusebius Pamphilus, Ecclesiastical History, (Grand Rapids: Baker Book House, 1991), 185.

[4] Marcion held to the view called docetism, which claims that Jesus only appeared to be human but did not truly become a man.

[5] Translated by Alexander Roberts and William Rambaut. From Ante-Nicene Fathers, Vol. 1. Edited by Alexander Roberts, James Donaldson, and A. Cleveland Coxe. (Buffalo, NY: Christian Literature Publishing Co., 1885.) Revised and edited for New Advent by Kevin Knight. <http://www.newadvent.org/fathers/0103434.htm>.

[6] Irenaeus, Against Heresies, V.21.1; Translated by Alexander Roberts and William Rambaut. From Ante-Nicene Fathers, Vol. 1. Edited by Alexander Roberts, James Donaldson, and A. Cleveland Coxe. (Buffalo, NY: Christian Literature Publishing Co., 1885.) Revised and edited for New Advent by Kevin Knight. <http://www.newadvent.org/fathers/0103521.htm>.

[7]  Irenaeus, Against Heresies, V.21.2; Translated by Alexander Roberts and William Rambaut. From Ante-Nicene Fathers, Vol. 1. Edited by Alexander Roberts, James Donaldson, and A. Cleveland Coxe. (Buffalo, NY: Christian Literature Publishing Co., 1885.) Revised and edited for New Advent by Kevin Knight. <http://www.newadvent.org/fathers/0103521.htm>.

[8] Luke 4:4

[9] Henry Chadwick, The Early Church: The story of emergent Chrstianity from the apostolic age to the dividing of the ways between the Greek East and the Latin West (London: Penguin Books, 1993), 81.

[10] Irenaeus, Against Heresies, III.11.8

[11]  Henry Chadwick, The Early Church: The story of emergent Chrstianity from the apostolic age to the dividing of the ways between the Greek East and the Latin West (London: Penguin Books, 1993), 81.

[12] Irenaeus, Against Heresies III.3.3

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Andrew Menkis

Andrew Menkis holds a B.A. from the University of Maryland in Philosophy and Classics and an M.A. in Historical Theology from Westminster Seminary California. He is a high school Bible teacher whose passion is for teaching the deep things of God in ways that are understandable and accessible to all followers of Christ.

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