Warfield provides helpful insights into John’s teaching on the Antichrist: “he makes three declarations concerning Antichrist which appear to traverse its implications. He transposes Antichrist from the future to the present. He expands him from an individual to a multitude. He reduces him from a person to a heresy.”  These three observations undermine the bulk of modern Antichrist discussion.
John’s readers are hearing that though Antichrist is not yet on the scene, he nevertheless “is coming.” but John informs them that this “antichrist” “is now already in the world” (1Jn 4:3). As Warfield notes “that post-posited ‘already’ [carries] with it the utmost strength of assertion.” John writes: “this is the spirit of the Antichrist, which you have heard was coming, and is now already in the world” (1Jn 4:3b). John clearly warns them that that which they “heard was coming” is “now already in the world.” In addition, he remarks: “As you have heard that the Antichrist is coming, even now many antichrists have come” (1Jn 2:18). Due to the appearing of these antichrists, his readers should understand that “it is the last hour” (1Jn 2:18). They are not harbingers of a distantly future Antichrist, for their presence is the signal that “the last hour” has already “come” (gegonasin). The “even now” emphasizes the presence of that which they fear (“as you heard”).
An objection from one amillennialist theologian against postmillennialism is postmillennialism’s removal of the antichrist not only from our future expectation but from the very center of time: “more and more that kingdom of darkness comes to manifestation as time progresses. At the very center of time therefore, stands the development of the Antichristian world power. Really, postmillennialism has no room for Antichrist in its thinking. . . . Antichrist cannot be taken seriously.” 
In redirecting his readers’ focus from the Antichrist’s future to his contemporary existence, John points out that the Antichrist is a movement, rather than an individual. In dealing with the idea of “the Antichrist,” he writes: “even now many antichrists have come” (1Jn 2:18). In fact, Antichrist is a “spirit” (1Jn 4:3) that pervades these many “antichrists” (1Jn 2:18), which involve “many deceivers” (2 Jn 7). Such views as Hoekema’s are surely mistaken: “The New Testament also teaches us to look for a single, final antichrist in the future (see 2Th 2:3–4).” 
Antichrist really is not a multitude of people, but rather the “spirit” (1Jn 4:3) among them that promotes deception (2 Jn 7) regarding Christ. “Who is a liar but he who denies that Jesus is the Christ? He is antichrist who denies the Father and the Son” (1Jn 2:22). John clearly applies the conception of the one Antichrist (ho antichristos) to the generic tendency to promote lies about the identity of Christ. He repeats this point in his second letter: “For many deceivers have gone out into the world who do not confess Jesus Christ as coming in the flesh. This is a deceiver and the antichrist [ho antichristos]” (2Jn 7). Thus, “according to 1 John, what is to be dreaded about the Antichrist is not the unleashing of awesome destruction but the fomenting of heresy.” 
On the basis of these four references we learn that Antichrist is not an individual, malevolent ruler looming in our future. John was “not looking to the appearance of some supernatural being in the prophesied future.” Rather, Antichrist is a contemporary heretical tendency regarding the person of Christ, which is current among many in John’s day. Hoekema errs when he writes: “Yet it would not be correct to say that John had no room in his thinking for a personal antichrist, since he still looks for an antichrist who is coming.”  As we shall see below, the beast of Revelation and the man of lawlessness are also contemporary realities in the first century — though wholly distinct from Antichrist.
1. Warfield, “Antichrist,” Selected Shorter Writings, 1:358.
2. Herman Hanko, “An Exegetical Refutation of Postmillennialism,” 25–26.
3. Anthony Hoekema, The Bible and the Future, 70.
4. Robert Fuller, Naming the Antichrist, 17.
5. Hoekema, Bible and the Future, 158.