The mention of lies versus truth in verse 21 leads John quite naturally to an analysis of the Gnostics’ errors. But it is not their errors in general that he seizes upon but rather the fundamental error which is their denial that Jesus is the Christ. Indeed, as he states it, this is not only the Gnostics’ error but also the most fundamental error that can be made by anyone. Therefore, it also has the most serious consequences. In writing about this denial of Jesus as the Christ John calls it the lie and the one who embraces it the liar.
To gain the full force of John’s statement one must recognize that the confession “Jesus is the Christ” does not mean merely that Jesus is the Messiah of Old Testament expectation. This is involved, of course, but much more is involved too. For if this were all the statement means, it is hard to see how the Gnostics could be opposed to it. Here the context throws light on the statement; for in the very same verse and in the next verse John goes on to speak of Jesus as the Son, that is, as the Son of God, and of knowing the Son in the Father and the Father in the Son. In other words, it becomes clear from the context that John is thinking of a confession of Christ’s full divinity. It is the belief that God became incarnate in Jesus as the Christ. This, incidentally, also makes sense of the historical situation in respect to the Gnostics. For the one thing that is most certainly known about them, particularly in the form of gnosticism popularized by Cerinthus in Asia Minor, is that they believed that the divine Christ, conceived as an emanation from the highest and superior God, came upon the man Jesus at the time of His baptism and left Him before His crucifixion.
This type of gnosticism is not so foreign to some forms of modern biblical criticism, for it is reflected in the kind of scholarship that would drive a wedge between what is called “the historical Jesus” and the “Christ of faith.” To do this is heresy, of course. Moreover, it is a heresy with terrible consequences, as one might expect. First, says John, to deny the Son is to deny the Father. No doubt the false teachers would have pretended to be worshiping the same God as the Christians. “We only differ from you in your views about Jesus,” they might have said. But John says that this is impossible and quite obviously so. For if Jesus is God, then to deny Jesus as God is to deny God.
Moreover, it is also to forfeit the presence of God in one’s life or, as we could also say, to have no part of Him or He of us. John uses the phrase “has the Father.” In biblical language this is the equivalent of saying that the one who will not confess Jesus as the Christ remains unregenerate and therefore under God’s just condemnation. On the other hand, the one who finds Christ finds the Father also and both possesses and is possessed by Him.
Twice in this section John has identified the denial of Jesus by the false teachers as the work of antichrist; that is, as the work of a terrifying demonic influence upon the congregations to whom he is writing. But if that is so, then the Christians might well ask, “But what can we do against it? How can we guard ourselves against this adversary?” John’s answer is that they are to make use of the two main weapons of defense that have been given to them.
The first of the Christians’ weapons is the word which they had heard from the beginning. Clearly, this refers to the Gospel or basic apostolic teaching which they had heard at the beginning and which they had believed. In its fullest sense, however, it refers to the entire teaching of the Word of God. They are to let this Word abide in them and therefore guide and form them. By contrast, they are not to neglect it or minimize it while running off in a search for some new thing.