This dissertation argues that eighteenth-century British authors often employed atheism to explore both the limits of modern selfhood and the limits of literary representation. Authors like Jonathan Swift, Sarah Fielding, Phebe Gibbes, and William Cowper imagined godless worlds dominated by atheists and atheistic tenets to interrogate Lockean and later Scottish Enlightenment understandings of the self. These authors cast the atheist as the fundamental incarnation of a completely autonomous self, and they each raised the issue of that self's ability (or, more accurately, inability) to integrate successfully into a wider community defined by developing notions of civility, sociability, and fellow feeling. Perhaps unsurprisingly, this atheistic self was found wanting. For the authors discussed throughout “Unbelief,” a truly sociable self was a believing self. And, because atheism barred one from sociability, theists from all corners of Britain's empire were entitled to participate, if in varying degrees, in the believing world these authors promoted. How authors went about this was counterintuitive. Instead of directly addressing atheistic arguments in the manner of sermons and apologetic tracts, literary works instantiated a speculative genre that takes atheism's premises for granted, depicting worlds in which God is absent and atheists rule the roost. Hence, the narrator of Swift's An Argument Against Abolishing Christianity (1708) begins by informing us that two men recently discovered there is no God. Swift notably satirizes these British atheists by juxtaposing them to Turkish Muslims, who to their credit still believe in God. Although Swift most certainly felt little attraction to Islam, it is nonetheless telling that the chasm between real, substantive Christianity and the religions Britain encountered in the East was narrowed for him by the more troubling presence of atheism at home. In response to atheism's perceived spread, this chasm continued to shrink throughout the century. Thus, just as texts like Swift's Argument present speculative fictions meant to forestall the rise of real-world unbelief, so too did religious pluralism arise, at least in part, as a reaction against atheism.