This book is the first extensive historical analysis of the relationship between empire and the Victorian secularist movement. Historians have paid little attention to the role of empire in the development of organized free thought. Secularism as it developed in Britain and its settler colonies was an overtly outward-looking, global ideology in a period marked by the rise of scientific rationalism and belief in the logic of a European civilizing mission. Recent scholarship has focused on how the empire influenced British and American atheists on the question of race. What is missing is an in-depth examination of the formation of secularist ideas about universal progress, ethics, and secular morality. Through an examination of the secularist periodical and pamphlet press, this book argues that the religious diversity of the British Empire helped to shape the ethical worldview of the secularists, providing ammunition for their critiques of Christian morality and the church and justification for their policy reform proposals both in Britain and the colonies.