"Little children, it is the last hour, and as you have heard that antichrist is coming, so now many antichrists have come. Therefore we know that it is the last hour" (1 John 2.18).
In 1 John 2.18 the Apostle John enters into direct confrontation with false teachers, a confrontation that indirectly had already determined the preceding exposition. And it is not a final confrontation. The theme is taken up again in 1 John 4.1 and in 1 John 5.4.
While the false teachers are identified as πλανῶντες ὑμᾶς (“those deceiving you”) in 1 John 2.26, in our verse they are recognized as ἀντίχριστοι (“antichrists”). With this designation John refers to the time-honored apocalyptic expectation (καθὼς ἠκούσατε, “as you have heard”) that the Antichrist will appear at the end of time. When John says: καὶ νῦν ἀντίχριστοι πολλοὶ γεγόνασιν (“and now many antichrists have come”), he historicizes the single anticipated Antichrist.
So the antichrists are the false teachers and everyone who denies that Jesus is the Christ (1 John 2.22). Anyone who does not “confess” Christ alone (1 John 4.3) and/or who does not acknowledge that Jesus has come in the flesh (2 John 7) is an antichrist.
Further, the fact that these antichrists have arisen is the sign ὅτι ἐσχάτη ὥρα ἐστίν (“that it is the last hour”). For it is without a doubt that Jesus’ coming is the last hour for the κόσμος (“world”). Now, it is specifically Jesus’ coming to which the deniers of Christ indirectly testify. And to this extent this assertion has the same meaning as 1 John 2.8: “the darkness is passing away and the true light is already shining.” This ever present “shining” is precisely what can and should be confirmed for believers by the very appearance of the false teachers.
"And this is the judgment: the light has come into the world, and people loved the darkness rather than the light because their works were evil" (John 3:19).