Religion is the set of beliefs and practices that give people a sense of order in their lives, provide them with meaning, and make it possible to live life as a project. It is a remarkably broad concept that includes not only the established world religions such as Judaism, Christianity, Islam and Hinduism, but also religious beliefs that are new, uncommon, not part of a formal church or sect, subscribed to by only a small number of people, or that seem illogical or unreasonable to others.

Many philosophers have attempted to define the term “religion.” The most commonly used definitions are substantial: they determine that someone is a member of a religion if they believe in a particular kind of reality. Such a definition is inadequate, however, because it fails to capture the way that religions develop and what their essence really is.

One can find functional definitions of religion in Emile Durkheim, who defines it as whatever system of practices creates solidarity among a group of people (whether or not those practices involve belief in unusual realities), and in Paul Tillich, who defines it as the axiological function that provides orientation in life. These functional definitions are more accurate than the substantive ones, but they can be problematic, too. For instance, they tend to treat religions as a monothetic set of beliefs and practices, which leads to the common assumption that all human cultures have religion.

Philosophers have also developed a theory of the nature of religion that does not use a substantive definition but instead focuses on the functions that religions perform. This approach, called a functionalist theory of religion, allows us to see how a variety of different religions share a similar underlying structure and how they evolve and become more complicated over time.

It also helps us to understand why there are so many differences between religions and why some of them appear to be more successful than others. This is because religions provide maps that enable people to deal with (or accept) the many limitations that stand across the project of their lives.

Religions give people ways to achieve the most important goals imaginable, some of which are proximate (a wiser, more fruitful, more charitable, or more successful way of living) and some of which are ultimate (the final condition of this or any other person, or of the cosmos itself).

Moreover, because they can be a source of strength in times of difficulty, religions are often the main source of moral guidance for society. This is why they have been so important to people throughout history and continue to be today. They are an essential element in what might be called the “socialization” of the human mind and body. Without them, we would be much less able to deal with the challenges of our environment and the many pitfalls that lie in our path. Moreover, they give us a sense of security and confidence that can free our minds to explore what might be possible for us.