Religion is a remarkably diverse phenomenon. It consists of beliefs, values, practices, ceremonies, rituals, holy places, and symbols that are central to a person’s life. It is often rooted in an individual’s relationship with a supreme being or divinity, although it may be more generally concerned with spirituality and morality. It is also a source of social cohesion and stability, the inspiration for art and architecture, literature, poetry, music, dance, drama, and film. It is at the root of societal ethics and laws, and it has contributed to the development of astronomy, mathematics, biology, and other fields of science.

Yet the term “religion” is notoriously difficult to define. Most attempts at definitions focus on the idea that religion involves a belief in a distinctive kind of reality or in the existence of gods or spirits. Such stipulative definitions, however, are often problematic. They are either too broad or too narrow, and they tend to ignore the fact that there are people who do not believe in these things.

A different approach focuses on the role that religion plays in society, rather than on the ideas and symbols that comprise it. This functional definition grew out of the work of three social theorists active in the wake of 19th century European industrialization and secularization: Emile Durkheim, Max Weber, and Karl Marx. Their goal was to examine how the religious aspects of a culture were used to sustain and control it, especially the power and financial exploitation that are so common in contemporary religions.

The use of the concept of religion as a social taxon is controversial, especially since cognitive science can explain many of its features without reference to hidden mental states. Some scholars reject stipulative definitions of religion, while others argue that to define religion by beliefs alone is an ideological bias and that it is important for scholars of religion to shift attention from beliefs to the institutional structures that produce them.

Some of the latest discussions about the nature of religion have been influenced by Wittgenstein’s notion of family resemblance, in which a social category does not have a single essence but only a set of crisscrossing and partially overlapping features like those found in a variety of games. This approach to the study of religion is known as polythetic.