A radical cultural and political history of exorcism and possession from the 1950s to the present day. Once considered an outdated embarrassment, demands for exorcism have increased since the mid-twentieth century, becoming a popular product in our therapeutic marketplace and a weapon against groups that resist state, corporate, and ecclesiastical powers. Are the 'possessed' suffering from mental health problems? Is the world falling victim to the devil and demons? Charting the history of exorcism in an allegedly secular age — from the brainwashing panic of the postwar period to the cult deprogramming of the 1970s, and from the massive influence of William Peter Blatty’s The Exorcist to the harmful practice of conversion “therapy” — Purging the Devil is an inquiry into the nature of belief and a meditation on our fascination with evil.