Religion is a vast, sprawling collection of beliefs and practices. It includes everything from a single god or goddess to an all-powerful deity, from rituals to moral codes, from belief systems to cults. Religion is a social taxon and its vast diversity evokes a lot of discussion. Whether to call some things religious and others not is a key question in such matters as public policy, psychotherapy, education, and the media. But the answer is not so simple as it seems. There are two philosophical issues at play. One involves the concept of social kinds, and the other concerns how to evaluate definitions in general.
The development of the concept of religion is an object lesson in how a term can shift from a specific sense to a more general one and back again. In its original sense, religion was the name for scrupulous devotion to a god or goddess (or, alternatively, to any kind of organized group). It was this sense that Cicero used in his condemnation of Roman religio and Epicurean Lucretius contrasted with vera religio (true worship of the one true god) and falsa religio (false worship).
Today the word “religion” is used as a taxon label for sets of social formations. Its paradigmatic examples are the so-called world religions of Judaism, Christianity, Islam, Hinduism, Buddhism, and Confucianism. It is also used to describe the religions of a specific place or people, and there are many more practices that have been given this label.
Some scholars have attempted to define what counts as a religion, and these have been divided into monothetic and polythetic approaches. Monothetic definitions rely on the classical view that every instance accurately described by a concept will share some defining property with the examples of the category. Polythetic definitions, on the other hand, use a prototype theory of concepts, in which cases are assessed not for their accuracy but for their usefulness.
The broadest definitions are functional, in which religions are defined as systems for monitoring, coding, protecting, and transmitting information of the highest possible value, from person to person and across generations. It is the axiological function of providing orientation for life that makes these informational systems worthy of the name “religions” and that gives them their universality.
Religions protect that which is indispensable for human life and flourishing of a kind—from sex to salvation, from family relationships to the meaning of life, from health to the proximate goal of being, from the ecstatic to the transcendent. Religions help people to organize and prioritize their values in a way that is conducive to the realization of these goals.
The fact that human beings need to organize and prioritize their values is a necessary condition for the existence of religions, but it does not explain why certain values are more valuable than others. This is a deeper question that is beyond the scope of this article, but it may be useful to consider some ways in which different values can be distinguished, and how those distinctions can be evaluated.