The Catholic Church espouses that the devil is not only real, but fully responsible for all that's evil in the world. While demonic possessions are controversial within the Church, the Bible is deals with the phenomenon through stories that reference both good and evil. Yet, in the last century, both rationalism and scientific methods are being used to explain "possessions" rather than referring to them as a paranormal phenomenon or force grounded in the demonic. .
There's a tension between the Church and science in an effort to explain if there are such things as good and evil. An example of this tug-of-war is demonstrated in the film, "The Exorcist," (1973) directed by William Friedkin. The male protagonist is a man of science and a man of God and the film delves into his struggle between what is good and what is evil, the secular and religious.
In many religions, the devil represents pure evil. The bible states, "He that committeth sin is of the devil; for the devil sinneth from the beginning. For this purpose the Son of God was manifested, that he might destroy the works of the devil."(John 3:8) .
The Bible is a constant story of good versus evil and in The Exorcist we see that through the battle with Regan's demon that claims to be the devil himself. The film deals with demonic possession very effectively through accurate religious evil. By creating various religious realism, viewers start to see a blurred line between what is film and what is truth. With the lack of computer aided special effects at the time and limited development of this genre before the release of this film, the audience could very easily see the events on screen taking place in real life. Shaking of the bed, vomiting and obscene dialog aid in that belief. During the climax of the film, quick cuts between Regan/Demon and Father Damien Karras show the tension and spiritual fight portrayed much like an action fight sequence might be edited.