Today is the feast of St. Irenaeus of Lyon, Doctor of the Church. He was born to a Christian family in Smyrna (now Izmir, Turkey), somewhere around AD 130, and in his youth heard the teaching of St. Polycarp (also from Smyrna), who was a student of St. John. Somewhere between 160 and 180, he became a priest in Lyon under St. Pothinus, the first bishop of Lyon. He visited Pope St. Eleutherius at some point in the 170s on an official mission concerned with the heresy of Montanism. The persecution of Marcus Aurelius was going on at the time; like all imperial persecutions, it was sporadic and patchy, but Lyon happened to face a crack-down on Christianity while Irenaeus was away; Pothinus was executed and Irenaeus was elected bishop when he returned. As bishop, he published against Gnosticism, and is still one of our major sources on it. There was the inevitable extended period during which scholars assumed that his accounts of Gnostics were fictional or at least highly exaggerated, but, while there's no need to assume that he necessarily got everything right, rediscovery of actual Gnostic works has consistently shown him to be at least in the neighborhood. He appealed, successfully, to Pope St. Victor I to be lenient in the Quartodecimian controvery, but for the most part his episcopal tenure seems to have been quite uneventful. We have no certain information about how he died; on some calendars he's listed as a martyr, but there doesn't seem to be any plausible story, or indeed, any story at all, about how that would have happened.
From Adversus Haereses, Book 3, Chapter 1:
We have learned from none others the plan of our salvation, than from those through whom the Gospel has come down to us, which they did at one time proclaim in public, and, at a later period, by the will of God, handed down to us in the Scriptures, to be the ground and pillar of our faith. For it is unlawful to assert that they preached before they possessed "perfect knowledge," as some do even venture to say, boasting themselves as improvers of the apostles. For, after our Lord rose from the dead, [the apostles] were invested with power from on high when the Holy Spirit came down [upon them], were filled from all [His gifts], and had perfect knowledge: they departed to the ends of the earth, preaching the glad tidings of the good things [sent] from God to us, and proclaiming the peace of heaven to men, who indeed do all equally and individually possess the Gospel of God. Matthew also issued a written Gospel among the Hebrews in their own dialect, while Peter and Paul were preaching at Rome, and laying the foundations of the Church. After their departure, Mark, the disciple and interpreter of Peter, did also hand down to us in writing what had been preached by Peter. Luke also, the companion of Paul, recorded in a book the Gospel preached by him. Afterwards, John, the disciple of the Lord, who also had leaned upon His breast, did himself publish a Gospel during his residence at Ephesus in Asia.
These have all declared to us that there is one God, Creator of heaven and earth, announced by the law and the prophets; and one Christ the Son of God. If any one do not agree to these truths, he despises the companions of the Lord; nay more, he despises Christ Himself the Lord; yea, he despises the Father also, and stands self-condemned, resisting and opposing his own salvation, as is the case with all heretics.
