1Jn 4, 3 The spirit of the antichrist is already in the world

(1Jn 4, 3) The spirit of the antichrist is already in the world
[3] And every spirit that does not acknowledge Jesus does not belong to God. This is the spirit of the antichrist that, as you heard, is to come, but in fact is already in the world.

(CCC 678) Following in the steps of the prophets and John the Baptist, Jesus announced the judgement of the Last Day in his preaching (cf. Dan 7:10; Joel 3-4; Mal 3:19; Mt 3:7-12). Then will the conduct of each one and the secrets of hearts be brought to light (cf. Mk 12:38-40; Lk 12:1-3; Jn 3:20-21; Rom 2:16; 1 Cor 4:5). Then will the culpable unbelief that counted the offer of God's grace as nothing be condemned (cf. Mt 11:20-24; 12:41-42). Our attitude to our neighbour will disclose acceptance or refusal of grace and divine love (cf. Mt 5:22; 7:1-5). On the Last Day Jesus will say: "Truly I say to you, as you did it to one of the least of these my brethren, you did it to me" (Mt 25:40). (CCC 675) Before Christ's second coming the Church must pass through a final trial that will shake the faith of many believers (Cf. Lk 18:8; Mt 24:12). The persecution that accompanies her pilgrimage on earth (Cf. Lk 21:12; Jn 15:19-20) will unveil the "mystery of iniquity" in the form of a religious deception offering men an apparent solution to their problems at the price of apostasy from the truth. The supreme religious deception is that of the Antichrist, a pseudo-messianism by which man glorifies himself in place of God and of his Messiah come in the flesh (Cf. 2 Th 2:4-12; 1 Th 5:2-3; 2 Jn 7; 1 Jn 2:18, 22). (CCC 676) The Antichrist's deception already begins to take shape in the world every time the claim is made to realize within history that messianic hope which can only be realized beyond history through the eschatological judgement. The Church has rejected even modified forms of this falsification of the kingdom to come under the name of millenarianism (Cf. DS 3839), especially the "intrinsically perverse" political form of a secular messianism (Pius XI, Divini Redemptoris, condemning the "false mysticism" of this "counterfeit of the redemption of the lowly"; cf. GS 20-21).