Psychology of religion consists of the application of psychological methods and interpretive frameworks to the diverse contents of religious traditions as well as to both religious and irreligious individuals. The various methods and frameworks can be summarized according to the classic distinction between the natural-scientific and human-scientific approaches. The first cluster amounts to objective, quantitative, and preferably experimental procedures for testing hypotheses about causal connections among the objects of one's study. In contrast, the human-scientific approach accesses the human world of experience using qualitative, phenomenological, and interpretive methods. This approach aims to discern meaningful, rather than causal, connections among the phenomena one seeks to understand.
Psychologists of religion pursue three major projects:
systematic description, especially of religious contents, attitudes, experiences, and expressions
explanation of the origins of religion, both in the history of the human race and in individual lives, taking into account a diversity of influences
mapping out the consequences of religious attitudes and conduct, both for the individual and for society at large.
The psychology of religion first arose as a self-conscious discipline in the late 19th century, but all three of these tasks have a history going back many centuries before that.
The challenge for the psychology of religion is essentially threefold:
to provide a thoroughgoing description of the objects of investigation, whether they be shared religious content (e.g., a tradition's ritual observances) or individual experiences, attitudes, or conduct
to account in psychological terms for the rise of such phenomena, whether they be in individual lives
to clarify the outcomes—the fruits, as William James put it—of these phenomena, for individuals, and the larger society. These fruits may be both positive and negative.
The first, descriptive task naturally requires a clarification of one's terms—above all, the word religion.