A form of religious belief in which Christian values are turned upside down, Satan is worshipped and God is reviled, Ritual is upended (as in the Black Mass), and behaviour normally thought of as Evil is promoted while "virtues" (like humility) are condemned. The origin of Satanism may lie as far back as Gnosticism (> Gnostic Fantasy), and certainly for centuries the religious establishments of the West tended to accuse those they wished to scapegoat (Cathars, Witches, etc.) of being Satanists. All the same, the 19th-century vogue for Satanism, and the behaviour of the lifestyle fantasists who thought of themselves as Satanists, seems literary in origin (> Satan).
The term is of some use in the study of Supernatural Fiction. Authors (some of them advocates of or dabblers in Decadence) like Charles Baudelaire, Marjorie Bowen, Aleister Crowley, Gustave Flaubert, Anatole France, J K Huysmans and Oscar Wilde made ironic use of the reversal of values represented by the belief. The extent to which any individual writer actually ascribes to Satanism presumably varied. The wave of Horror tales and movies following Ira Levin's Rosemary's Baby (1967), filmed as Rosemary's Baby (1968), and William Peter Blatty's The Exorcist (1971), filmed as The Exorcist (1973), brought Satanism renewed popularity as a theme. [JC]