Religion is a cultural phenomenon with so many different forms and beliefs that it is hard to pin down. Yet, despite its difficulty to define, it appears to be a universal human need and experience. It is a contested concept that is a subject of study in anthropology, history, sociology, philosophy, psychology, religious studies, and even cognitive science. Because it cuts across disciplinary lines, scholars have come to recognize that definitions of religion vary widely. Some are very broad, such as Paul Tillich’s (1886-1965) claim that religion involves “ultimate concern,” and others are quite narrow, such as the idea that a religion is only a belief in one god or spiritual being.

The debate about how to describe religion is a key issue in the social sciences and humanities, and the way it plays out has profound consequences. Scholars have argued that the way we define a concept determines the kind of analysis that will be applied to it. For example, some of the first attempts to analyze religion used a classical approach based on the assumption that if something is correctly described as a particular type of object, it will share a set of defining properties with all objects in that category. These were called “substantive” definitions. The twentieth century, however, saw the rise of a more reflective view that rejected the assumption that things are identical and took inspiration from Ludwig Wittgenstein’s notion of “family resemblance” to categorize objects. These were called “functional” definitions.

One reason that functional definitions gained popularity is that they are more inclusive than substantive ones. People can believe in supernatural beings and cosmological orders without having a religion. And a religion may exist in one culture without being present in any other cultures. The result is that functional definitions can capture a variety of social phenomena and a wide range of experiences.

Nevertheless, there are philosophical issues that arise for the contested concept of religion, and these problems are likely to surface with other abstract concepts used to sort cultural types (e.g., literature, democracy). One is that a social genus like religion can be understood in terms of secondary characteristics that can help explain its presence in various societies and cultures. Yet, the existence of these social ties suggests that the term should be treated as a family resemblance concept rather than as an object with necessary and sufficient properties.

A second philosophical issue is that it is possible to have a religion even without believing in god or goddesses. In such cases, the belief is that there are natural forces or spiritual energies that can be manipulated through rituals in order to control the environment, including weather, pregnancy and birth, and the success of hunting. This form of religiosity has been analyzed by some scholars as a secular form of religion.