Irenaeus

Against Heresies is a five-book refutation written about 180 by a bishop of Lugdunum, the Roman city that is now Lyon, and the five volumes are those five books. Irenaeus set out to describe the Gnostic teachings he opposed before arguing against them, and the description is why the work still matters to historians who do not share his side of it: for centuries it was the fullest surviving account of what those groups actually taught, until Coptic texts turned up at Nag Hammadi in 1945 and could be set beside it. He argues from a rule of faith held openly by churches able to name their teachers back to the apostles, against knowledge said to pass privately from master to pupil. Almost none of the Greek original survives; what is read is a Latin translation of uncertain date. Irenaeus came from Smyrna and said he had heard Polycarp preach when he was a boy.