The struggle with Gnosticism, as we have seen, involved a consideration of the right exegesis of the Fourth Gospel over a broad front. Subsequent heresies, and particularly the Arian controversy, involved a similar consideration of the right exegesis of the Gospel on the narrower front of Christological interpretation. This issue had been one important feature in the arguments with the Gnostics. Irenaeus had even declared the refutation of a dualist Christology to be the very purpose of the writing of the Gospel. But in fact at that stage it was only a single strand among many. In the centuries that followed it became the issue of all-absorbing importance.

The Valentinian Christology (in so far as the very limited and sketchy evidence allows us to judge) had been built up on a onesided application of such texts as John x. 30 and John xiv. 6. The orthodox had replied with an insistence on those texts which emphasised his real humanity. But they had also to meet the theories of men like Theodotus, who could point to such a text as John viii. 40 and claim that it proved Jesus to be a mere man and no more. Origen clearly recognised that the fundamental fault in both these types of heresy was the arbitrary exclusion of a part of the evidence in the interests of an apparently more consistent picture of Christ, either as straightforwardly divine or entirely if superlatively human. It was evident that what was needed was a more careful statement of the divine and human elements in the person of Christ.