Religions are culturally distinctive sets of beliefs and practices that are based on the existence of one or more supreme beings, cosmos, or spirit(s). Religion also involves the moral conduct of believers, worship, or prayer, ritual and meditative practice, and participation in religious institutions. Religious life teaches people how to live and what is right and wrong. It offers people a framework for dealing with the uncertainty of life, and a goal toward which to strive (either in this life or the next).

The definition of “religion” has changed over time. It now includes not only traditional, organized religions such as Christianity, Judaism, Islam, Hinduism, and Buddhism, but also beliefs and practices that are new or uncommon, not part of a formal church or sect, only subscribed to by a few people, or seem illogical or unreasonable to others. It also extends to the moral beliefs of atheists and agnostics.

A growing number of philosophers have addressed questions about religion. These philosophers include continental philosophers such as Martin Heidegger, Jacques Derrida, and Simone de Beauvoir, and analytic philosophers such as Bertrand Russell, G.E. Moore, and Alan Sokal. In addition, there is a significant amount of work by philosophers trained in anthropology, sociology, and philosophy of culture who study religion from an analytical perspective.

Many of these philosophical analyses have been monothetic, in that they operate under the classical view that every instance accurately described by a concept will have a defining property that puts it in that category. The last several decades, however, have seen a rise in polythetic approaches to defining religion. These approach the notion of a religion as a family-resemblance concept instead of as a necessary and sufficient property.

The reason for the shift is a recognition that the concepts used to sort a variety of different cultural activities may have assumptions baked into them, and that these assumptions can distort the understanding of these activities.

For example, Durkheim argued that religion is real because it reinforces social stability in at least two ways. It gives people a common set of values and thereby promotes socialization; and it establishes rituals that bring together members of a community physically (such as houses of worship) or facilitate communication among them (e.g., prayers).

These goals can be proximate, such as creating a more productive, charitable, or successful way of living, or ultimate, such as achieving the heavenly bliss that some religions promise after death. In either case, they make the project of human life a little easier, because they help people recognize and cope with the various kinds of limitations that confront all projects of life, including the limits of this universe and the possibility of rebirth.