Religion is one of the most fundamental forces in human history, and it has been a key force in the development of knowledge, art, and technology. It has also been both a source of liberation and coercion, with religious groups often developing in cooperation with or in opposition to the institutions of their societies. The study of religion has long been one of the major disciplines in the social sciences, and many of its leading figures have been pioneers in bringing a more sociological perspective to the understanding of both the diversity and universality of religion.

A common definition of religion defines it as a human being’s relation to that which is held to be sacred, holy, absolute, spiritual, divine, or worthy of especial reverence. In some traditions, this is expressed in terms of a belief in spirits or gods; in others, it is a concern with the nature of human life and the natural world. A common function of religion is to provide moral guidance, with the corresponding expectation that individuals will behave according to those guidelines. Religions have a variety of social functions, including stabilizing communities and giving people an identity. They can help people cope with the uncertainty of life and give them maps for navigating through it. They can offer a sense of purpose and meaning, as well as a sense of belonging, and they may even organize hierarchies, with particular individuals deemed to be invested with a special sort of spiritual or moral authority.

They can also encourage moral behavior and thus contribute to the maintenance of the order of society. They can teach people about their place in the universe, guiding them to live in a way that is consistent with that place, and they can provide a framework for understanding the world, which helps to promote scientific inquiry. But they can also lead to violence and wanton bloodshed, as when individuals or entire communities or nations persecute their members on the basis of their religious beliefs.

This is why it is important for the study of religion to understand how these various functions interact with each other. In the twentieth century, there has been an effort to drop the traditional substantive definition of religion in favor of a functional one. Emile Durkheim argued that religion is whatever system of practices unites a number of people into a single moral community, and Paul Tillich used the term to refer to the dominant concerns that serve to organize a person’s values (whether or not they involve beliefs in any unusual realities). These are “functional” definitions, and they are based on the recognition that religions have an essential role in human lives.