Irenaeus, the Bishop of Lyons was born around AD 130 and grew up in Smyrna where Polycarp was the bishop. He was a defender of the orthodox view of who Jesus was and is viewed as one of the major contributors to the emergence of a unified, catholic Christianity.
He was a leading figure in establishing the canon of Scripture because he was one of the first to answer such questions as: Which texts are authoritative? How should they be interpreted? By what authority do they speak? Whose interpretations are correct? Thus, his main arguments were that the catholic church had to draw their authority from the same place that the apostles drew theirs': the Old and the New Testaments of the Bible and not "fanciful narratives and cosmic mythology".
One of his most significant works was The Detection and Overthrow of What is Falsely Called Knowledge" which was aimed at the false teachings of the Gnostics and their so-called "knowledge". Today it is simply known as Against Heresies.