The Age of Reason; Being an Investigation of True and Fabulous Theology is a deistic pamphlet, written by eighteenth-century British radical and American revolutionary Thomas Paine, that criticizes institutionalized religion and challenges the legitimacy of the Bible. Published in three parts in 1794, 1795, and 1807, it was a bestseller in America, where it caused a short-lived deistic revival. British audiences, however, fearing increased political radicalism as a result of the French Revolution, received it with more hostility. The Age of Reason presents common deistic arguments; for example, it highlights what Paine perceives as corruption of the Christian Church and criticizes its efforts to acquire political power. Paine advocates reason in the place of revelation, leading him to reject miracles and to view the Bible as an ordinary piece of literature rather than as a divinely inspired text. It promotes natural religion and argues for a creator-God.
Most of Paine's arguments had long been available to the educated elite, but by presenting them in an engaging and irreverent style, he made deism appealing and accessible to a mass audience. The book was also inexpensive, putting it within the reach of a large number of buyers. Fearing the spread of what they viewed as potentially revolutionary ideas, the British government prosecuted printers and booksellers who tried to publish and distribute it. Paine nevertheless inspired and guided many British freethinkers of the nineteenth and twentieth centuries and his influence and spirit endures in the works of contemporary writers like Christopher Hitchens.