This fascinating study explores the interests and motivations that led fifty-three English clergymen to join the Royal Society of London between 1663 and 1687. An important contribution to a deeper understanding of science and religion in the Restoration period, this study contends that the doubts the Society raised about the certainty of human knowledge influenced these clergymen's understanding of the nature of belief and their defense of Christian mysteries like the Trinity and the Incarnation. By focusing on the ways they defined the term, 'belief', a correlation can be established between their stand on the problem of certainty and their success in answering critics of the mysteries of Christianity.