I was in way over my head. Somehow, I had managed to sneak my way into an upper-level seminary class for which I was woefully unprepared. I was like a kid who, having just learned his multiplication tables, suddenly found himself sitting in trigonometry.

The class was on the writings and theology of St. Irenaeus, a second century bishop in the city of Lyon (ancient Gaul, modern France). After the first session, I approached the prof to ask for his suggestions on an essay topic. I’ll never forget his response, “Chad, I suggest you examine the connection between the Eucharist and recapitulation in Adversus Haereses.”

Gulp.

Eucharist. Ok, I knew that was a fancy Greek name for the Lord’s Supper. But recapitulation? Adversus Haereses? No clue. I remember hightailing it toward the library, repeating the prof’s suggestion over and over, lest it slip my mind before I could write it down.

And so began, however falteringly and humorously, my lifelong fascination with one of the most important teachers of the early church, one who had a living link to the apostles themselves.

A Student of the Student of John the Apostle

Irenaeus was born around AD 130. He studied under Polycarp, who himself had been a student of John the Apostle. Irenaeus says of Polycarp that he “always taught the things which he had learned from the apostles, and which the church has handed down” (Against Heresies. 3.4).

Just imagine that: how would you like to study under a teacher who himself had been a student of the disciple whom Jesus loved? Sign me up!

Irenaeus had plenty of opportunities to take what he had learned, from Polycarp and others, and put them into practice. Though born in Smyrna (modern-day Turkey), he ended up in the Roman province of Gaul, as part of the Christian community there. While he was away on church business in Rome, persecution against believers broke out back home, the bishop died, and upon Irenaeus’ return, he took his place. For the next 20+ years, Irenaeus was bishop and missionary in that region. He died, possibly by martyrdom, around AD 200.

The Champion of the Incarnation

Though the Lord Jesus used Irenaeus to minister to people in his own time and place, he also used him as (what Roman Catholics call) a Doctor of the Church, that is, one on a relatively short list of teachers who have made significant contributions to theology.

Call him a church father, call him a Doctor of the Church, call him Bishop of Lyon. For my part, Irenaeus will always wear the title “Champion of the Incarnation.” He understood, better than anyone I have ever read, the full implications of the fact that God the Creator took on our created flesh to redeem this created world through the very stuff of creation.

Why was this so vital to Irenaeus? For one, this was thoroughly biblical, part of his theological heritage from John via Polycarp. But for another, Irenaeus and his fellow Christians of the second century were increasingly enveloped by a toxic miasma of an over-the-top spiritualizing religion called Gnosticism.

The Popular, Toxic Religion of Gnosticism

Taking its name from gnōsis, the Greek word for knowledge, the Gnostics claimed to have a higher, secret knowledge. Although they were by no means monolithic, the various Gnostic groups could shake hands over one basic premise: this world of dirt and rocks, trees and animals, human flesh and blood, is gross and unspiritual and unworthy of any connection to the true God.

This visible world was a failed project slapped together by a junior deity. All of us humans, who have a spark of divinity trapped inside these bags of flesh, are stuck here for now. Freedom or salvation is begun by realizing the gnōsis that this created world is evil, our human bodies are a hindrance to true spirituality, and what matters is the residue of “god-ness” imprisoned inside each of us.

To spread their popular message, Gnostics cherry-picked biblical passages, here and there, twisting them to suit their false teachings. You’ve likely stumbled upon claims that there are “Lost Gospels” out there, somehow “removed” by the church. This is baseless nonsense, but those who urge this are referring to so-called “Gospels” penned by Gnostic sects—texts which we never considered canonical, much less removed from the Bible.

In a famous passage from Irenaeus, he says the Gnostics are like men who disassembled the mosaic of a king, rearranging the jewels and gems to form the image of a dog, then claiming this is what the king looks like (Against Heresies. 1.8). So they rearrange Scripture texts, weaving in their own baseless myths, to concoct heretical dogmas that pull the wool over the eyes of the ignorant.

Against Heresies

Two works by Irenaeus have been passed down to us: Demonstration of the Apostolic Preaching and Refutation and Overthrow of Knowledge Falsely So Called. The latter is usually called the less-than-a-mouthful title, Against Heresies [in Latin: Adversus Haereses]). In this work, divided into five books, Irenaeus took on the monumental task of describing the beliefs of various Gnostic sects and then refuting them, based upon Scripture and the Rule of Faith, an early creed-like summary of the Bible.

If you’ve never read Against Heresies, what are you waiting for? Stop reading this article immediately, call your boss and tell him you’re not coming into work, turn your phone off, download a copy onto your Kindle, make a pot of strong coffee, and sit there for the next 24 hours doing nothing but absorbing it. You can thank me later.

What Irenaeus does is walk us through the Scriptures, Old Testament and New Testament, to demonstrate the coherence of the biblical story, from creation to incarnation to eschaton. Far from being the work of a flunky deity, creation is the beautiful work of the only true God.

In this world, he also made humanity, not because “he stood in need of man, but that he might have someone upon whom to confer his benefits” (4:14). Isn’t that a golden sentence? God created us so he would have someone upon whom to bestow his favor, his love, his gifts. That is why we exist, because of the love of God.

Unlike the heretical Gnostics, whose noses were held high away from creation in their uber-spirituality, Irenaeus preached the earthy Gospel of the creating God who is not embarrassed by the stuff that he made.

“The glory of God,” Irenaeus says, “is a living man [or ‘a man fully alive’]” (4.20). And that life consists of beholding God. That we might see God, the Father has made himself known to us in his Son, who took on our human nature, was present in this creation, and saved it, that we might participate in the glory of the Father. We are made fully alive in Jesus, who came that he might “vivify those who receive and behold him through faith (4:20).

Unlike the heretical Gnostics, whose noses were held high away from creation in their uber-spirituality, Irenaeus preached the earthy Gospel of the creating God who is not embarrassed by the stuff that he made. He took into himself created matter, “attaching man to God by his own incarnation” (5.1). And he still uses the stuff of creation, like the bread and wine of the Eucharist, to make us fully alive by communion in his body and blood (5.2).

Summing Up All People in Christ

If there’s one word that sums up what Irenaeus taught about the saving work of Jesus, it’s the five-dollar word recapitulation. In Greek, recapitulation is anakephalaiōsis, which means a “summing up” or “bringing together.” When Jesus became man, as Adam had been a man, he “summed up [recapitulated] in himself all nations dispersed from Adam downwards, and all languages and generations of men, together with Adam himself” (3.22).

Jesus brings together, in his human body, every human from Adam onward. You, me, Adam, your meth-head cousin and your gossipy Grandma—we are all in Jesus, who has undone and redone our sinful history that he might make us fully alive in communion with the Father through the Holy Spirit, to the glory of his name. He is the head of a new humanity. From him, our head, divine life flows into us, his members, so that we are renewed bodily, as creatures, to reflect the glory of our Creator.

Unfortunately, Gnosticism, rather than passing out of existence, is alive and still spreading its cancer today. It just goes by the variety of names associated with popular cultural spiritualities, talk of the god within, even a rejection of how God formed us as males and females (as if our created biological realities don’t matter). Even in churches, where our bodies are treated as “shells” or “prisons” of the soul, we hear the Gnostics happily clapping along.

So let us revisit Irenaeus, this very modern yet ancient teacher of the church. He first began to teach me, thirty years ago, when I was a wet-behind-the-ears theologian. My essay for that class, well, it was a B- at best. But by it, I was introduced to an A+ Doctor of the Church. He, more than any other father of the church—ancient, reformational, or modern—has shaped what I teach and believe about the implications of the Word becoming flesh.

Get his works. Immerse yourself in them. You will not be disappointed in this Champion of the Incarnation.