Believers and non-believers often take it for granted that traditional religious faith is, in principle, incapable of the sort of justification which might be given to a scientific theory. Yet how are scientific theories justified and is it the case that religious belief cannot satisfy the same standards of rationality? Based on a critical examination of recent accounts of the nature of science and of its justification given by Kuhn, Popper, Lakatos, Laudan, and Newton-Smith, this book contends that models of scientific rationality which are used in criticism of religious belief are in fact often inadequate as accounts of the nature of science. It is argued that a realist philosophy of science both reflects the character of science and scientific justification, and also suggests that religious belief could be given a justification of the same sort.