Christian Thinkers 101: A Crash Course on Irenaeus


Irenaeus was one of the first Christians to defend the faith against Gnosticism, but what exactly did he believe and what else did he contribute to Christianity? Here’s your crash course on the life and accomplishments of Irenaeus—and why he still matters today.

Who Was Irenaeus?

Irenaeus (c. 130–202) was a Greek thinker who was born in Asia Minor to a Christian family. His historic connections to early Christianity ran deep, as he was a student of the apostolic father Polycarp (69–155). Christian tradition asserts that Polycarp actually knew the apostle John—so Irenaeus wasn’t too far removed from the time of the apostles. Irenaeus was both a sophisticated theologian and a careful apologist. In fact, he was the first Christian apologist to defend Christianity from specific heresies (false teachings that deny essential Christian doctrines). Irenaeus defended Christianity from the influential heresy known as Gnosticism. He also wrote about the early Christian church having four Gospels that were distinct from the counterfeit Gnostic Gospels. Irenaeus was also a leader in the church and ultimately became the bishop of Lyons. There is a late tradition that Irenaeus was martyred, but this claim is not well supported by historical evidence and is rejected by modern scholars.

What Did Irenaeus Write?

Irenaeus’ two most important books are Against Heresies and Demonstration of the Apostolic Preaching. The first book is a defense of Christianity and a critique of early Gnostic claims. The second is a catechism (a summary of Christian teaching) that includes both apologetic and pastoral themes since Irenaeus was also a spiritual shepherd in the early Christian church.


What Did Irenaeus Believe?

Christians of various traditions continue to uphold beliefs articulated by Irenaeus. Perhaps Irenaeus’ three most important Christian apologetics accomplishments are the following:

  1. Irenaeus critiqued Gnosticism, a heretical religious philosophy that affirmed esoteric knowledge, dualism (spirit is good, matter is evil), and a transcendent non-creator God above Jehovah.
  2. Irenaeus critiqued Marcionism, a heretical religious philosophy that affirmed Jesus as the savior and Paul as his chief apostle, but rejected the Hebrew Bible and the God of Israel.
  3. Irenaeus critiqued the false Gnostic Gospels and differentiated them from the four apostolic Gospels.

Why Does Irenaeus Matter Today?

Irenaeus is sometimes criticized for his atonement theory known as the recapitulationism (the view that Christ’s atonement reversed the course of humankind from disobedience to obedience), yet he is an important early Christian theologian and apologist. His critiques of the potent heresies of Gnosticism and Marcionism helped protect Christianity from doctrinal corruption. Irenaeus also helped connect apostolic Christianity with the later church fathers. He is significant in his role of affirming the distinctive apostolic orthodoxy. It is said that Irenaeus was known for seeking to carefully understand competing heresies and then attempting to provide Scriptural and historical arguments against them. It would appear that Irenaeus practiced the golden rule of apologetics: Treat other people’s beliefs the way you want yours treated (carefully, fairly, accurately). Irenaeus is important today because he helps connect the doctrinal truths of apostolic Christianity with the faith’s later development. Furthermore, Irenaeus provides important background information about who authored the various biblical books and what their purposes were in being written.

Other articles in the Christian Thinkers 101 series: St. Augustine; C. S. Lewis; Blaise Pascal; St. Anselm; St. Athanasius; St. Thomas Aquinas; Jonathan Edwards; Søren Kierkegaard; St. Bonaventure; Martin Luther; John Calvin

Reflections: Your Turn

Irenaeus defended Christianity from heretical teachings. What can Christian churches do today to help their people avoid false doctrine?


  • For an examination of Irenaeus’ life and accomplishments, see Getting to Know the Church Fathers: An Evangelical Introduction by Bryan Litfin.

  One thought on “Christian Thinkers 101: A Crash Course on Irenaeus

    • August 30, 2016 at 10:10 am

      Thanks, Vincent.

      Ken Samples

  1. August 30, 2016 at 8:08 am

    Another phenomenal post in a great series. I need to bump him up my list. Currently reading through Origen and loving it.

    • August 30, 2016 at 9:55 am

      Hello, JW.

      The church fathers are a great theological and apologetics resource for us today.

      Best regards.

      Ken Samples

  2. Esther Ziol
    September 6, 2016 at 9:47 am

    How can the church help believers avoid heresies? How about a very basic course on hermeneutics? The errors we see today seem to be those that re-interpret the Bible in ways never meant by the Author of scripture.

    • September 6, 2016 at 4:27 pm

      Thank you, Esther, for your comments.

      Sound hermeneutical principles are critically important.

      Best regards in Christ.

      Ken Samples

  3. Rita Gorski
    September 6, 2016 at 10:10 am

    I appreciated that you noted that Irenaeus appeared to use the golden rule of apologetics: treat other people’s beliefs as you would want yours to be treated – carefully, fairly, accurately. Something to remember in all our communications with others. We could add respectfully, but that may be implied in the others. I’ve so enjoyed this “course.” Thank you.

    • September 6, 2016 at 4:25 pm

      Thanks again, Rita, for your thoughtful comments.

      The Golden Rule of Apologetics is difficult to do but when it is done it is very powerful.

      Best regards.

      Ken Samples

  4. Scott
    September 16, 2016 at 5:30 am

    I read through Irenaeus last Autumn, as a matter of fact, and one comment created a whole lot of questions for me. It’s his view of Jesus being crucified while in his mid-to-upper 40s. He includes this view as part of his recapitulation theory (which you mentioned above). But the problem for me was that that theory didn’t seem to be the sole reason for his unique view on Jesus’ age at death. Rather, he claimed an extra-biblical/historical basis — or at least confirmation — for it. In Book 2, Chapter 22 (see e.g. here: he specifically noted having received information from those who knew the apostles themselves! Here’s a relevant quote:

    Now, that the first stage of early life embraces thirty years, and that this extends onwards to the fortieth year, every one will admit; but from the fortieth and fiftieth year a man begins to decline towards old age, which our Lord possessed while He still fulfilled the office of a Teacher, even as the Gospel and all the elders testify; those who were conversant in Asia with John, the disciple of the Lord, [affirming] that John conveyed to them that information. And he remained among them up to the times of Trajan. Some of them, moreover, saw not only John, but the other apostles also, and heard the very same account from them, and bear testimony as to the [validity of] the statement.

    Now, I’m not trying to open up a can of worms here. (Seems to me Irenaeus did that himself!) And I’m not sure if there’s really anything biblically wrong with the idea that Jesus did, in fact, die at such an age. (Is there?) But, for what it’s worth, I’ve tried to do what research I could on this and haven’t found anything satisfactory so far in dealing with this claim.

    Basically, though, it would appear to me that, with reference to our use of Irenaeus’ writings, if one is NOT going to accept Irenaeus’ view of Jesus’ age, the logical corollary is that one must then be somewhat careful and not treat his information as accurate without further confirmation. In other words, if he provides his own eccentric interpretation of a passage or theological point, that’s one thing. But when he does so while claiming as a source of information those who knew the very Apostles, what are we to do? We can, if we wish, impugn one of the links in the chain: 1) the Apostles (never!), 2) those who knew them well (not likely either), 3) Irenaeus’ interpretation of what they said (or what he thought they said), etc. But wouldn’t that also mean taking with a grain of salt his other historical claims, not matter how much we covet them in our desire to defend the integrity of Scripture? And this would include, as you noted above, his provision of “important background information about who authored the various biblical books and what their purposes were in being written.” We seem to require some other early Church authority to vindicate Irenaeus before we can accept any historical claim, no?

    • September 18, 2016 at 6:27 pm



      I’m not familiar with the age of Jesus issue connected to Irenaeus. Historians range Jesus dates from 7-4 B.C. – A.D. 28-33. Some would narrow the dates to 4 B.C. – A.D. 30 or 33 (Harold Hoehner: Chronological Aspects of the Life of Christ). The narrowed dates come closer to the 33 years age that many accept. So we don’t know Jesus’ exact age at death though the narrowed dates above seem reasonable if not likely.

      It seems to me that the church fathers were overall both reliable and important as theologians and apologists of early Christianity. Yet some of the fathers were much more scholarly and careful than others. I think Augustine stands as the greatest of all the church fathers. But sometimes the fathers got things wrong and/or had exotic or erroneous views. Thus the views of the fathers need to be carefully examined.

      I would think that the apostles would have known Jesus’ general age through interacting with his mother Mary. So the fact that there appears to have been a controversy about his age strikes me as a bit puzzling. But fortunately Irenaeus’ important identification of the Gospel authors is supported by other church fathers such as Papias and by historical-textual considerations.

      Thanks for sharing this with me.

      Best regards in Christ.

      Ken Samples

  5. September 22, 2016 at 4:55 pm

    Christian churches today should equip their members with continual instruction that is Christ-centered, and focused on God’s holiness and eternal perspective, not our finite mind’s thoughts of how things should be. God’s plan for redemption of His people by His grace alone through faith in the Son Christ alone is a common thread that ties together every book of the Bible, even when not direct or obvious. Along with the truth of the Gospel, churches should pound into their members the underlying paradoxical principles of righteousness made possible by evil, strength made possible by weakness, triumph made possible by trials, glory made possible by humility, and life made possible through death. Our lives are made full when motivated by gratitude, submission, and service, not by self-serving attempts to feel good or to be popular in the world’s eyes. False doctrine always arises from mankind’s desire to claim some degree of sovereignty away from God.

  6. November 27, 2016 at 7:15 pm

    Reblogged this on Is Christianity True?.

    • November 27, 2016 at 10:09 pm

      Thanks, Steve.

      Ken Samples

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