Irenaeus Writes Against Heresies

Irenaeus, bishop of Lyon in Gaul, whose writings Catholic tradition counts among the church fathers, wrote five books exposing and refuting the Gnostic systems, especially the school of Valentinus. He answered them from the Scriptures of both Testaments and the rule of faith, insisting that the one God who made the world is the Father of Jesus Christ. He also appealed to the succession of bishops in churches founded by apostles, especially Rome, an argument later used to support the claims of the Roman see.