The psychology of religion studies religious experience, belief, and practice as features of the mind and personality, examining conversion, mysticism, prayer, ritual, and their emotional and cognitive workings. Its foundational text is William James's The Varieties of Religious Experience (1902), which set the tone for the descriptive, respectful study of religious experience: James distinguished the "healthy-minded" from the "sick soul," analyzed conversion and mystical states in their own terms, and judged religion pragmatically by its fruits in the life of the believer rather than by the truth of its doctrines.
A quite different current runs through Sigmund Freud, who explained religion reductively, as an "illusion" rooted in the projected wish for a protective father, and as a form of collective obsessional neurosis, while Carl Jung, breaking with him, treated religious symbols far more positively, as expressions of the archetypes of the collective unconscious and as vital to psychological wholeness. The twentieth century added the study of religious development (the stages of faith), the psychology of conversion and of religious coping, and the attachment-theory analysis of the believer's bond with God. More recently the cognitive science of religion has sought to explain the recurrence of religious ideas in terms of the ordinary workings of human cognition, our tendency to detect agency, to attribute minds, and to remember "minimally counterintuitive" concepts. The field ranges, in short, from the sympathetic description of the inner life of faith to the attempt to explain religion as a natural product of the human mind.