I think for an interesting discussion we should look at the beloved apostle Johnâs text in full:
Beloved, do not believe every spirit, but test the spirits, whether they are of God; because many false prophets have gone out into the world. By this you know the Spirit of God: Every spirit that confesses that Jesus Christ has come in the flesh is of God, and every spirit that does not confess that Jesus Christ has come in the flesh is not of God. And this is the spirit of the Antichrist, which you have heard was coming, and is now already in the world. [1 John 4:1-3; NKJV]
John speaks of discerning the spirits, as there are many false prophets, and then goes on to give a trait of a false spirit: any one who âdoes not confess that Jesus Christ has come in the flesh is not of Godâ is speaking in âthe spirit of the Antichrist.â What does the beloved apostle mean when he says âdoes not confess that Jesus Christ has come in the fleshâ? Both Muslims and Christians agree that Jesus had a physical body, and even atheists who believe Christ was simply a man believe that he had a physical body, ergo that he âcame in the flesh.â
What St. John is referring to here, however, is the Incarnation. The Gnostics, whom John fought against personally, did not believe that Christ had a physical body as the physical world was seen as pure evil, and so many heresies said that Christ was fully spirit (which is why so many of them, such as the Docetists, denied the crucifixion, as a spirit cannot suffer). Christ was fully man and fully God - at the Incarnation, the Divine Word maintained His deity but took on human flesh. St. John focused on this argument for nearly all of the first chapter of his gospel. To deny the Incarnation was to deny the reality of Jesus, which John here condemns.
The argument John is presenting in 1 John 4:1-3, therefore, must be understood within the Christian context. It must also be understood that while St. John identifies one singular Antichrist (such as in Revelation), he also identifies plural Antichrists or âthe spirit of the Antichristâ and warns that both are already present in the world (as he does here). While I am not calling every single Muslim an Antichrist (God forbid) the teachings of Mohammad and the Quran are indeed the Spirit of the Antichrist and, while they donât deny Christ coming in the flesh, they deny Christ coming in His divine glory and the reality of the Incarnation, just as the Gnostics did. To a Christian, that is a very dangerous teaching.