(1) Docetism.—In the first place, John may mean that the opponents simply denied the reality of the earthly life of Jesus. Such a form of error is by no means unknown in the history of the Church. It is called "Docetism." According to Docetism the Son of God did not really live a human life—with human sufferings and a human death—but only appeared to do so.
(2) Cerinthus.—In the second place, the meaning of the passage may be that the opponents denied the unity of the person of Jesus Christ. Compare ch. 2:22. Some persons in the early Church supposed that there were two separate persons in the figure that is described in the Gospels. A heavenly being, the Christ, it was thought, united himself with the man Jesus at the time when the dove descended after the baptism. Matt. 3:16,17. Such was the view of Cerinthus, who is declared by tradition to have been an opponent of the apostle John at Ephesus. It has been suggested, therefore, that it was actually Cerinthus, with his disciples, who is combated in the First Epistle of John.
(3) Denial of the Incarnation.—Both Cerinthus and the Docetists denied the reality of the incarnation—both denied that the Son of God actually assumed a human nature and lived a complete human life. According to Cerinthus and others like him, the Christ stood only in somewhat loose relation to the man Jesus. He was united with him only late in life, he left him before the crucifixion. On this view, it was not the Christ who lay in the manger at Bethlehem, it was not the Christ who suffered on the cross. Cerinthus, like the Docetists, kept the Son of God out of any close relation to the world and to us.
(4) John's Reply.—Against some such view as one of these, John was concerned to establish the reality of the incarnation—the truth that "the Word became flesh." In the Gospel, that truth underlies the whole of the narrative; in the First Epistle it is directly defended against the opposing error. It is defended first of all by an appeal to what the writer had seen and heard. "We knew Jesus in Palestine," says John in effect, "and we can testify that Jesus himself was none other than the Christ, the Son of God." I John, 1:1-4.
(5) John, the Opponents, and Cerinthus.—The false teachers who are combated in the epistle had apparently withdrawn from the Church and formed a separate sect. I John 2:19. Their separateness of mind and heart and life had found expression in open schism. Whether they are to be identified with disciples of Cerinthus is at least doubtful. False speculation about the person of Christ no doubt assumed many forms in the closing years of the first century.
5. CONNECTION BETWEEN THE SECOND AND THE THIRD EPISTLE
In III John 9, the apostle tells Gaius that he had written "somewhat unto the church." This letter to the church may have been written at some previous time. It is also possible, however, that it was written together with the letter to Gaius. The Greek word for "I wrote" admits of that interpretation. If that interpretation be correct, then John perhaps means to say that although he has written a letter to the church he could not in that letter urge the hospitable reception of the missionaries. For the present, the influence of Diotrephes was too strong. The letter to the church had to be concerned with other matters.
If this view of the letter mentioned in III John 9 be adopted, then the Second Epistle of John corresponds to the description. The Second Epistle is addressed to a church, and it is written with some reserve. If "certain" of the children of "the elect lady" were walking in truth, II John 4, the inference is that others were conducting themselves very differently. Evidently there was danger of false teaching among the readers. Hospitality to men like Demetrius and his companions could hardly be expected of such a church. If hospitality should be practiced, it was only too likely to be hospitality to men of a very different stamp. Vs. 10, 11.
Possibly, therefore, the Second Epistle of John is actually the letter that is referred to in III John 9, a letter to the church of which Gaius was a member. This hypothesis is supported by the striking formal similarity of the two letters. They are of almost exactly the same length; the openings and especially the conclusions, II John 12, 13; III John 13, 14, are couched in almost exactly the same terms. They look very much like twin epistles, written on two sheets of papyrus of the same size.
Of course the hypothesis is by no means certain. Perhaps the letter referred to in III John 9 was a previous letter bespeaking hospitality, which had failed of its effect. When the apostle saw, from the answer or lack of answer to the previous letter, that the church was ill disposed, he had recourse to an individual member of it. Even in this case, however, it remains probable that our two epistles were written at about the same time.