In a century dominated by the exacting methods and dramatic successes of science, it is difficult to imagine an informed contemporary religious believer never shaken by the doubt that his or her most sacred ideas are atavisms to a benighted age, vain and empty fantasies. To such a believer, Freud's late monograph, The Future of an Illusion, with its warm, solicitous tone, but relentless scepticism, must seem the patient knell of his or her worst fears. For here Freud uses his dialectical skill and his psychoanalysis to augment motives for self-doubt at least as old as Abraham: Perhaps the most cherished of my beliefs are a kind of madness, a condition I do not recognize because it is so widely shared. Perhaps like the madman bewitched by the tapestry of his delusions, I hold fast to my faith only because I could not endure the threadbare fabric of a life without it. But it is not as though the religionist is utterly without defence against this source of doubt, nor that the familiar defence is without considerable prima facie force against Freud. For when sceptics such as Freud turn their account of the origin of religious faith into a case against the truth of religious claims, the believer can attack this line with an unassailable axiom: No examination of the motives for a belief is relevant to an assessment of its truth. To assume otherwise is to commit the genetic fallacy. The question I want to deal with here is whether the religious believer should rest content with this rejoinder to Freud.