Why did Irenaeus the Bishop of Lyons write - Against Heresies?

Even in heresy there is “nothing new under the sun” (Ecclesiastes 1:9 NIV) The false teachings that spring up in and around the church remain much the same.
Instead of turning to Christ’s atoning works, many have sought to save themselves by discovering some secret knowledge. In the early church, it appeared in a group of heresies called Gnosticism (gnosis is a Greek word meaning “knowledge”).

Before the founding of the church, some form of Gnosticism apparently existed. When John wrote his first epistle, he struck a blow at this false teaching. Yet it still had a following in the second century.

We know little about Irenaeus, the man who opposed Gnosticism in the latter part of the second century. He was probably born in Asia Minor in about 125. Active trading between Asia Minor and Gaul had allowed Christians to bring their faith to Gaul, where they had established a vigorous church in the chief city, Lyons.

While he served as an elder in Lyons, Irenaeus lived up to his name, which means “peaceful,” by traveling to Rome to ask the bishop there to extend leniency to the Montanists in Asia Minor. During this mission, persecution arose in Lyons, and the bishop there was martyred.

Irenaeus became bishop in his place and found that Gnosticism had gained converts in Gaul. It had spread easily because the Gnostics used Christian terms—though they gave them radically different interpretations. The fusion of Christian terms with concepts from Greek philosophy and Asian religion appealed to those who wanted to believe they could save themselves without depending on the grace of the Almighty Father.

Irenaeus studied the forms of Gnosticism. Though they varied greatly, they commonly taught that the physical world was evil; that the world was created and is governed by angelic powers, not God; that God is distant and not really connected with this world; that salvation can be attained by learning special secret teachings; that spiritual persons (pneumatikoi)—that is, the Gnostics themselves—are superior to regular Christians (psychikoi). Gnostic teachers supported these ideas with the Gnostic Gospels—volumes that usually bore an apostle’s name and portrayed Jesus teaching Gnostic doctrines.

When the bishop of Lyons had learned about this heresy, he wrote Against Heresies, an enormous work in which he sought to unveil the foolishness of the “Gnosis Falsely So Called.” Drawing on Old and New Testaments, he showed that a loving God created the world, which became corrupted through human’s sin. Adam, the innocent first man, became sinful by yielding to temptation. But his fall has been undone—recapitulated—by the work of the second innocent man, Christ, the new Adam. The body is not evil, and at the last day believers’ bodies and souls will be raised; they will live with God forever.

Irenaeus understood that Gnosticism appealed to the human desire to know something others didn’t know. Of the Gnostics he wrote, “As soon as a man has been won over to their way of salvation, he becomes so puffed up with conceit and self-importance that he struts about with the air of a rooster.” But Christians should humbly accept God’s grace, not become involved in intellectual exercises that lead to vanity.

All his life Irenaeus had happily recalled his acquaintance with Polycarp, who had personally known the Apostle John, so perhaps it’s not surprising that Irenaeus appealed to the authority of the apostles when he disproved the claims of Gnosticism. The bishop pointed out that the apostles had taught in public, keeping nothing secret. Throughout the empire, the churches agreed on certain teachings that came from Christ’s apostles, and these alone formed the foundation of belief. 

By declaring the apostles’ successors, the bishops, guardians of the faith, Irenaeus enhanced the respect paid to bishops.

In Against Heresies Irenaeus set forth the standard for the church’s theology: All the truth we need is embodied in the Bible. He also proved himself the greatest theologian since the Apostle Paul. His widely circulated argument dealt a deadly blow to Gnosticism in his age.


Curtis, A., Lang, J. S., Petersen, R., & Curtis, J. S. L. A. K. (1998). 100 most important events in christian history, the. Grand Rapids, MI: Baker.