Irenaeus and the Gnostics

From Christian History:

God became flesh
The Gnostics who threatened Irenaeus's community tended to divide things into two realities—one good, the other bad. In response to such dualism, Irenaeus presented the unity of apostolic faith.

For example, Irenaeus' opponents divided "Christ" from "Jesus." Christ, they said, was a divine spirit-being from the heavenly realm (the Pleroma, or "fullness") who did not become really incarnate, so he could not really suffer. He was not truly human, but either only seemed to be human or temporarily inhabited a human named "Jesus."

But Irenaeus was too familiar with the constant threat of martyrdom to let such dualism deceive his flock. The real, bloody passion and death of Christ was a fundamental element of Christian faith. Martyrdom imitated it, and Christians confessed it in baptism and worship. Irenaeus responded with a strong biblical statement that Jesus Christ was one person, both divine and human, and that he really was crucified.

This is what gave comfort to those who were martyred: "[Christ] knew, therefore, both those who should suffer persecution, and he knew those who should have to be scourged and slain because of Him; and He did not speak of any other cross, but of the suffering which He should Himself undergo first, and His disciples afterward."

At the root of the Valentinian Gnostic myth known by Irenaeus was a division between two Gods: the supreme, transcendent Father revealed by Christ, and the arrogant Demiurge, the creator of the physical world, who was identified with the Old Testament God of the Jews. Therefore, the Gnostics divided reality into two opposing realms—the heavenly world of spiritual beings (named "Aeons") and the material world of trees, rocks, earth, flesh, and blood.

In contrast to this, Irenaeus declared: "But there is one only God … He is Father, He is God, He the founder, He the Maker, He the Creator, … He it is whom the law proclaims, whom the prophets preach, whom Christ reveals, whom the Apostles make known to us, and in whom the church believes." These words reveal another important theme for Irenaeus: the harmony between the Old Testament and the emerging New Testament, between the prophets and apostles. The Creator spoken of by Moses is the Father revealed in Christ. His redemptive plan has been the same throughout history.

The Valentinian Gnostics also taught that, since the material world was created by an imposter, an ignorant deity, it had no value and must perish. The human body, as part of the material world, could never be immortal. This is why Christ could not have been truly human and why, the Gnostics believed, there would be no bodily resurrection or redemption of the created order. Salvation was purely spiritual.

But according to Irenaeus, the "spiritual" person is made up of the "the union of [material] flesh and [the human] spirit, receiving the Spirit of God." God created the physical world, and so that world has value and will be redeemed and renewed someday. God created the human body, and the body will be raised again incorruptible and immortal.

Against the Valentinians, Irenaeus emphasized the supernatural, redemptive ministry of the Holy Spirit who renews both the body and the spirit. This ministry of the Holy Spirit strengthened the martyrs to bear witness unto death in hope of bodily resurrection. This promise was based on the reality of Christ's incarnation: "For if the flesh were not in a position to be saved, the Word of God would in no wise have become flesh."

The faith that saves
The Gnostics had an elitist understanding of salvation; they divided humanity into two categories, the "spiritual ones" who belong to the Father and the "material ones" who belong to the Demiurge. As the "spiritual ones," the Gnostic believed, they were destined for salvation because of the divine spark within them (unlike the rest of humanity, who are asleep and have no hope).

Not so for Irenaeus. All humans are fallen—dead in their sins—and in need of redemption. Salvation is not a matter of destiny but of faith. The eternal Son of God, who became human, reunited God with humanity. Those who believe in him have the life of the Holy Spirit in them—and only they can be called "spiritual": "as many as fear God and trust in His Son's advent, and who through faith do establish the Spirit of God in their hearts—such men as these shall be properly called both 'pure,' and 'spiritual,' and 'those living to God,' because they possess the Spirit of the Father, who purifies man, and raises him up to the life of God."

So we see in Irenaeus the great orthodox doctrines of unity: One God, who is the Father and Creator of all things, immaterial and material, and who orchestrates one harmonious history of revelation and redemption; one Savior, who is both divine spirit and human flesh, both Christ and Jesus; one human nature, which is both spiritual and fleshly; one salvation of both the spiritual and material realms, which is by faith.

These were the doctrines Irenaeus received from those who had passed the apostolic teaching down to him. This was the orthodoxy that protected his flock against the wolves of heresy and that gave Polycarp and the martyrs of Lyons and Vienne the faith to endure even to the end.