The young Christian faith was pushing west through the Roman Empire during the second century, as the earliest missionaries and evangelists were sent out from the churches of Asia Minor.
Polycarp was instrumental in this westward push, sending a man named Pothinus, whom he had taught, to southern Gaul. While establishing a church in Lyons, Pothinus was joined by another important disciple of Polycarp, Irenaeus.
In Irenaeus, we see again a student following in a master’s footsteps, building upon the spiritual foundation laid directly before by Polycarp and indirectly by Ignatius. We also have the first major leader who had no connection with the apostles.
In the midst of broad persecution, he fought against the heresies that threatened the young church. The biggest sect was Gnosticism, the same set of heresies that cropped up in the New Testament. In response, Irenaeus wrote his most famous work, Against Heresies, a five-volume set that outlined in excruciating detail the fallacies of the Gnostics and the truth of the Gospel.
Irenaeus is the first in our line that did not die as a martyr. But he faced some terrible adversities at the dawn of the church as Ignatius and Polycarp, and like them he stood with undaunted faith.