"Melancholy Duty" is a scholarly book that examines the complementary aspects of the thinking of David Hume and Edward Gibbon, particularly in relation to their engagement with 18th-century Christianity. In ten chapters, the iconoclastic work of these two thinkers is illuminated, with Hume regarded as a prominent philosopher and Gibbon as a consummate historian. The book analyzes how they attempted to naturalize the study of Christianity, focusing on its social and political dimensions. It offers a comprehensive and thorough exploration of the challenge that philosophical historiography poses to Christianity. Topics such as belief in miracles and the afterlife, fanaticism, superstition, and the nature of religious persecution are central to the critical engagement of Hume and Gibbon. This work makes a valuable contribution to various academic disciplines, including the history of ideas, religious studies, and philosophy, and is aimed at a broad audience of professionals and interested readers.