“The means of life is found in fellowship with God. But fellowship with God is to know God and to enjoy his goodness. Human beings therefore shall see God so that they may live . . . . The glory of God is a human being fully alive, and the life of a human being consists in beholding God.” 
These beautiful words were penned by a man who is probably my favorite theologian of the early church — Saint Irenaeus of Lyons. As the quote above reflects, St. Irenaeus was a thinker captivated by the pursuit of truth about God.
Although in earlier days I might have named St. Augustine of Hippo as my favorite church father, I now think Irenaeus sits solidly at the top of the list.
Here’s a quick rundown of his life and legacy, as well as the elements of his theology that most stand out to me.
A Pastor Zealous for Grace and Truth
Born in Asia Minor (which is now Turkey) around AD 130, Irenaeus later moved far to the west and became bishop of the church in Lyons (southern France), where he ministered from AD 177 until his death around 202. In his youth he sat under the teaching of Polycarp, who in turn was discipled by the apostle John — making Irenaeus only two generations removed from the apostles. As such, he serves as an important bridge between the era of the primitive church and that of the later major theologians and church councils.
Irenaeus’s name comes from the Greek word for “peaceful” (from which we also get our English word “irenic”), and evidently he lived up to it. In one of the only surviving fragments we have of his personal letters, the bishop recounts how early Christians disagreed on when to celebrate Easter and how many days to fast beforehand. In response, Irenaeus argued that this was an area where believers could follow their own customs and convictions. Ultimately what mattered most was that Christians live in harmony and respect each other’s decisions.
But there was one area where the bishop of Lyons refused to be peaceful. He vigorously combatted false teaching — particularly the heresies of Gnosticism and Marcionism that were rampantly spreading in his day.
Much like modern cult leaders, the promoters of these teachings were gaining converts by promising them secret knowledge of the “true” nature of God and how to be saved — for a manageable fee, of course! Irenaeus opposed these distortions of the gospel by constantly pointing people back to the Scriptures and the words of Christ so they could see the truth for themselves, and by reminding them of the true faith taught by the apostles and openly preached for free by the whole church throughout the world.
Irenaeus put a lot of legwork into his refutation of the various Gnostic theories. He read their commentaries, interviewed their followers, and even snuck into a few of their secret meetings, all in an effort to truly understand them before criticizing them. This culminated in the publication of one of the most important theological documents in the history of the church: the five-volume work fittingly known as Against Heresies.
Evidently his efforts were successful: after the publication of Against Heresies, Gnosticism was effectively snuffed out for hundreds of years until its modern reappearance as a part of the “New Age” movement.
Captivated by God’s Goodness
In my recent read-through of his hefty tome, I was struck by the depth and cohesiveness of Irenaeus’s theology. Though his project was largely polemical, intended to tear down a false system, Irenaeus’ Against Heresies manages to cover most of the topics you’d find in a modern textbook of systematic theology — God, creation, the fall, God’s covenants with Israel, Christ’s incarnation, salvation, life in the Spirit, ecclesiology, and even eschatology!
One of his greatest burdens in the book was to defend the truth of God’s goodness and, in turn, the goodness of his creation. At the heart of Gnosticism was a denial of the value of physical matter and an insistence that a good God could not have created such a broken world. Their solution to the problem of evil in the world was to posit that the universe was in fact made by a defective deity, a lesser god among a vast plethora of celestial beings. And thus, according to the Gnostics, the way to be saved from the prison of material existence was through “secret knowledge” of these higher gods (or “Aeons”).
It wasn’t hard for Irenaeus to demonstrate the incoherence of such beliefs, particularly since the various Gnostic teachers couldn’t even agree with each other over how many of these “Aeons” there were or which ones were higher than the others. But on a deeper level, the bishop of Lyons turned to Scripture to demonstrate that the true God is, in fact, the one who created the universe to be “very good,” a receptacle of his blessing, but that human disobedience to God resulted in the evil we experience.
Thankfully, God redeemed matter by taking a physical body himself in the person of Jesus of Nazareth, “who did, through His transcendent love, become what we are, that He might bring us to be even what He is Himself” (Against Heresies, Preface to Book V). The glorious historical reality of Christ’s incarnation, death, and resurrection has undone the curse of sin and death, opening up the true way for humanity to experience salvation and immortality — including the future resurrection of our bodies.
For Irenaeus, as for all orthodox Christians, creation matters. God values our bodies, and therefore what we do with our bodies matters to him. It is in the body that we worship him, and it is in the metaphorical Body of Christ — that is, the Church — that we are shaped by the preaching of the true gospel to become ready for spending eternity in the presence of God’s glory.
Irenaeus stood solidly within the mainstream of primitive Christian thought in his forceful insistence that God was not the author of evil. Rather, God endowed his creation with the free choice of whether to remain in relationship with him, “because God made man a free [agent] from the beginning, possessing his own power, even as he does his own soul, to obey the behests of God voluntarily, and not by compulsion of God. For there is no coercion with God” (Against Heresies, Book IV, ch. 27:1).
Willing to Wonder
In one of the few areas where Irenaeus allowed himself to venture into more speculative territory, it was in answering the charge of the Gnostics that God should never have given his creatures a free choice if he foreknew they would fall. This is where the bishop offers what scholars now refer to as the “Irenaean Theodicy,” an approach to the problem of evil that still merits consideration.
In short, he posits that only by offering such a choice, and allowing his human creations to undergo the process of discovery in losing and regaining God’s blessing, could God lead people to appreciate virtue of their own accord (Against Heresies, Book IV, ch. 27:6-7). God wanted creatures who were good by choice and not simply by preprogrammed nature, so that they could enjoy eternity with him all the more for having freely chosen it. Seen in this way, the presence of suffering and evil in the world becomes the necessary condition for the cultivation of true virtue in human souls.
Whether or not one finds his reasoning convincing, I for one think it’s a fascinating approach to a difficult topic. It’s clear that Irenaeus had a deep respect for the biblical depiction of God’s goodness and love, coupled with an awe and curiosity at the wonder of Christ’s incarnation. This was a man who refused to leave his brain at the door when worshiping his God, while also refusing to leave his heart of devotion out of his theologizing.
The depth of Irenaeus’s own learning, as well as his brilliance as a speculative theologian, shines through his writing. Even though we have earlier extrabiblical Christian documents, it could reasonably be said that Saint Irenaeus was the first great theologian of the church after the apostles. And the great thing is, his biggest contributions were not in the way of innovation, but simply articulation and explanation of orthodox Christian doctrine, preserving the gospel for subsequent generations.
My prayer is that all Christians would share his burden to see the Church built up by the clear preaching of gospel truth, as well as his passion for unity and peace among those who have embraced such truth.
 From Against Heresies, Book IV, chapter 20, sections 5-7. I’ve used the rendition found in James R. Payton Jr., Irenaeus on the Christian Faith: A Condensation of Against Heresies (Pickwick Publications, 2011),