The Enthusiast tells the story of a character type that was developed in early modern Britain to discredit radical prophets during an era that witnessed the dismantling of the Church of England's traditional means for punishing heresy. As William Cook Miller shows, the caricature of fanaticism here called the Enthusiast began as propaganda against religious dissenters, especially working-class upstarts, but was adopted by a range of writers as a literary vehicle for exploring profound problems of spirit, soul, and body and as a persona for the ironic expression of their own prophetic illuminations.

Taking shape through the public and private writings of some of the most insightful authors of seventeenth-century Britain—Henry More, John Locke, the Third Earl of Shaftesbury, Mary Astell, and Jonathan Swift, among others—the Enthusiast appeared in various guises and literary modes.

By attending to this literary being and its animators, The Enthusiast establishes the figure of the fanatic as a bridge between the Reformation and the Enlightenment, showing how an incipient secular modernity was informed by not the rejection of religion but the transformation of the prophet into something sparkling, witty, ironic, and new.