The Gospel of Saint John is said to have been one of the exorcist’s best defenses against the devil. It was said to have sent the possessing devil into fits. It was believed the medieval demonic could not stand to hear it read aloud. The following text appeared in the King James version of the Bible, much as the 16th and 17th century exorcists would have read it:
In the beginning was the Word, and the Word was with God, and the Word was God. The same was in the beginning with God. All things were made by him; and without him was not any thing made that was made. In him was life; and the life was the light of men. And the light shineth in darkness; and the darkness comprehended it not. (John 1:1-5)
And the Word was made flesh; and dwelt among us, (and we behold his glory, the glory as of the only begotten of the Father), full of grace and truth. (John 1:14)
The Gospel of St. John was supposedly used during exorcism because it was believed the idea of God becoming incarnate in Christ was something which the devil and demons could not stand. The reasoning behind the theory of God manifesting himself in man should be so disturbing to the devil is difficult to comprehend. All that is, if one believes it, is the act of Divine manifestation, God became man. It is a divine magical act – a mystery. The identical act has been ascribed to the devil and his demons many times. The devil has been said to manifest himself in a person. If the devil is believed to be able to do what God does, then why should such an act scare the devil so?
The same theory holds true in the case of the legendary vampire. It is held that a vampire is afraid of the crucifix. However, the vampire is the «undead,» a spirit that has materialized; his soul is or already has been, by belief, condemned to hell. Christ can no longer save or condemn him, thus reducing all cause for him to fear the crucifix. Obviously, objectively viewed, the devil’s fear in both incidents is for the living, to show them Christ wins over the devil or evil. Causally, one might observe, the crucifix serves as a quick end to vampire movies and caused Christians to feel less guilty for enjoying them. A.G.H.
Source: 4.