Few teachings in the Bible have been as wildly misunderstood as the teaching of the apostle John on the Antichrist. Opinions and speculation about him are commonplace. Unfortunately, the assumptions made about Antichrist are usually far away from the actual teaching of the Bible on the subject.
The Bible tells us it was the last hour two thousand years ago, and commentators have come up with many ingenious explanations in order to account for why we are all still here. The apostle John was describing the sweep of the second hand toward the hour of midnight. And here we sit, an aeon or so later, quietly listening to the creak of centuries, and still no Second Coming. Perhaps John was mistaken? But that is not an option for believers, and so a better place to look for mistakes, and with much greater promise for discovering them, is in our own understanding of what John is actually talking about.
What is the real nature of antichrist? The preterist view of such passages, and in my view the correct one, holds that Antichrist, a false teacher who sought to mislead the people of God, died two thousand years ago. So did the Beast, a civil ruler, who sought to destroy the people of God. Understanding that these things have already been fulfilled does not make us careless; quite the opposite. We learned from Solomon that nothing is new under the sun. Because antichrists are still among us, and beasts still seek to persecute us, we must come to understand how the faithful are called to respond to all the works of the enemy. The Antichrist is dead, but a liberal bishop who denies that Jesus is God enfleshed is a modern antichrist. The Beast is dead, but a civil ruler who wants to savage the people of God is a modern beast. Cerinthus and Nero are dead, but their modern counterparts are still very much alive. The fact that we are not dealing with the same Beast, or the same Antichrist, does not leave us without opportunities for application. How do we fight against their spiritual descendants? The way our fathers did, and one of the greatest things we need to learn is how to fight while honoring that which is diabolical (Rom. 13:1-5; Jude 8-9; Acts 26:25).
Incidentally, we may remark in passing that there is absolutely no basis in Scripture anywhere for the popular conflation of the Beast and Antichrist into one arch-fiend at the end of the world.
A clear sign of the end (of the Judaic aeon, not the world) was that certain false teachers had bolted from the church which John was addressing. A division between light and darkness is always necessary, and will always reveal itself over time. First he says, they went out. John says that these false ones departed (v. 19). This shows us how the doctrine of the perseverance of the saints is to be understood. The real believers had an anointing — because they had an anointing from the Holy One (the Lord Jesus), they knew all things (v. 20). They were established in the truth. And they were firmly grounded in the antithesis. John tells his people that they know the truth. He did not write to teach them, but to remind them (v. 20). But further, and this is very important, it is not enough to know the truth. They must know that no lie comes from the truth. It is not enough to affirm the truth. A man must always affirm and deny. If he refuses to deny, he does not really affirm.
The heresy which John had in his crosshairs is a heresy about the person of Christ. The arch-liar is the one who denies that Jesus is the Christ. Always remember that the issue is not words, but rather the referents of the words. What is meant by them? John teaches us here that the way of access to the Father is through the Son. A man who has the Son (which he cannot have unless he holds to the truth about the Son) has the Father also. A man who denies the Son has denied the Father also (vv. 22-23).
So there are two safeguards. The first is the gospel. The doctrine preached from the beginning must abide in them in order for them to abide in the Son and Father (v. 24). The end result of faithfulness to this doctrine is eternal life (v. 25). The second is the Spirit. Deceivers will come (v. 26). When they do, the anointing that believers have received abides in them, and they do not need some special Gnostic guru. They will be led by the Spirit to walk in the same way that they have been taught. The Spirit continues just as the true teaching continues.