Gnosticism

One of the earliest heresies to arise in the Christian church was Gnosticism, and Irenaeus was one of its chief early opponents. Not all Gnostics believed exactly the same thing, but the general outlines of the belief are fairly clear.

Gnostics were dualists, teaching that there are two great opposing forces: good versus evil, light versus darkness, knowledge versus ignorance, spirit versus matter. Since the world is material, and leaves much room for improvement, they denied that God had made it. “How can the perfect produce the imperfect, the infinite produce the finite, the spiritual produce the material?” they asked. One solution was to say that there were thirty beings called AEons, and that God had made the first AEon, which made the second AEon, which made the third, and so on to the thirtieth AEon, which made the world. (This, Gnostics pointed out to the initiate, was the true inward spiritual meaning of the statement that Jesus was thirty years old when he began to preach.) As Irenaeus pointed out, this did not help at all. Assuming the Gnostic view of the matter, each of the thirty must be either finite or infinite, material or non-material, and somewhere along the line you would have an infinite being producing a finite one, a spiritual being producing a material one.

The Gnostics were Docetists (pronounced do-SEE-tists). This word comes from the Greek word meaning “to seem.” They taught that Christ did not really have a material body, but only seemed to have one. It was an appearance, so that he could communicate with men, but was not really there. (If holograms had been known then, they would certainly have said that the supposed body of Jesus was a hologram.) They went on to say that Jesus was not really born, and did not really suffer or die, but merely appeared to do so. It was in opposition to early Gnostic teachers that the Apostle John wrote (1 John 4:1-3) that anyone who denies that Jesus Christ is come in the flesh is of antiChrist.

Gnostics claimed to be Christians, but Christians with a difference. They said that Jesus had had two doctrines: one a doctrine fit for the common man, and preached to everyone, and the other an advanced teaching, kept secret from the multitudes, fit only for the chosen few, the spiritually elite. They, the Gnostics, were the spiritually elite, and although the doctrines taught in the churches were not exactly wrong, and were in fact as close to the truth as the common man could hope to come, it was to the Gnostics that one must turn for the real truth.
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In opposition to this idea, Irenaeus maintained that the Gospel message is for everyone. He was perhaps the first to speak of the Church as “Catholic” (universal). In using this term, he made three contrasts:

(1) He contrasted the over-all church with the single local congregation, so that one spoke of the Church in Ephesus, but also of the Catholic Church, of which the Churches in Ephesus, Corinth, Rome, Antioch, etc. were local branches or chapters.

(2) He contrasted Christianity with Judaism, in that the task of Judaism was to preserve the knowledge of the one God by establishing a solid national base for it among a single people, but the task of Christianity was to set out from that base to preach the Truth to all nations.

(3) He contrasted Christianity with Gnosticism, in that the Gnostics claimed to have a message only for the few with the right aptitudes and temperaments, whereas the Christian Gospel was to be proclaimed to all men everywhere.
Irenaeus then went on to say: If Jesus did have a special secret teaching, to whom would He entrust it? Clearly, to His disciples, to the Twelve, who were with Him constantly, and to whom he spoke without reservation (Mark 4:34). And was the teaching of the Twelve different from that of Paul? Here the Gnostics, and others since, have tried to drive a wedge between Paul and the original Apostles, but Peter writes of Paul in the highest terms (2 Peter 3:15), as one whose teaching is authentic. Again, we find Paul saying to the elders of the church at Ephesus (Acts 20:27), that he has declared to them the whole counsel of God. Where, then, do we look for Christ’s authentic teaching? In the congregations that were founded by the apostles, who set trustworthy men in charge of them, and charged them to pass on the teaching unchanged to future generations through carefully chosen successors.
– Source: Biography of Irenaeus, Bishop of Lyons, theologian By James Kiefer