This introduction demonstrates atheism’s centrality in eighteenth-century British culture, and it illustrates the paradoxical ways in which atheism’s presence in the period’s literature was meant to prevent its presence in the real world. The chapter charts the history of British thinking about unbelief throughout the seventeenth and eighteenth centuries before arguing that fictional depictions of atheism as repulsive and unsympathetic gave rise to a unique form of believing selfhood, one defined not by creeds and doctrines but by affective rejections of unbelief. Moreover, the association of belief with sociability, and atheism with selfishness, led authors like Jonathan Swift, Alexander Pope, Sarah Fielding, Phebe Gibbes, and William Cowper to create ecumenical fantasies in which theists around the globe unite to curb atheism’s spread. These fictions nuance our understanding of secularization, demonstrating how atheism’s relationship to modernity is more fraught than is typically acknowledged, and revealing the profound role imaginative literature has played in sustaining belief.