Religion is a unified system of beliefs and practices that gives its followers something sacred to believe in, a spiritual concept or figure to worship, or something to cling to in times of crisis. It usually also involves a set of rules to follow and codes of conduct, as well as a sense of belonging to a larger community that can give them support during difficult times. Religions vary in their specific teachings and beliefs, but most of them deal in some way with salvation—either in a literal fashion, such as going to heaven after death in Christianity, or in a more symbolic manner, such as reaching nirvana in Buddhism. They also often involve cultural beliefs and worldviews, texts and prophecies, a place to go, rituals and ceremonies, symbols and trances, and moral teachings that have a spiritual significance for believers.
Throughout history, scholars have tried to categorize religions and to understand what distinguishes them from other cultural types. Most attempts have been “monothetic,” meaning that they operate under the classical view that a given concept can be accurately defined in terms of a single defining property. The last few decades, however, have seen the emergence of a different approach, one that uses polythetic classification, whereby the notion of a religion is understood as a social taxon that can be sorted into groups by virtue of the presence or absence of various characteristics.
These newer approaches to religion raise a number of philosophical issues. The most important is that they make it possible to classify a wide variety of practices as belonging to a category called religion without ever saying whether or not they actually correspond to any unusual realities. This shift from a substantive to a functional definition of religion is reflected in the work of Emile Durkheim and Paul Tillich, who define the concept as whatever set of practices unite a group of people into a moral community (whether or not those practices involve belief in any unusual realities).
Another issue arises when one considers that even within religions there is great diversity, with some people believing that their faith requires them to act in particular ways and others simply having certain moods or beliefs that are regarded as religious in nature. For this reason, the philosopher Kwame Anthony Appiah has suggested that maybe there isn’t such a thing as a religion at all—or at least that it is impossible to come up with a general definition of it.
In addition, many of the current definitions of religion include in their scope areas that most non-religious academics would regard as purely scientific, such as cosmology or ecology. This may be because some scholars are trying to show that the study of religion can benefit from the same kinds of critical skills used in other disciplines. Despite these obstacles, however, it seems likely that the study of religion will continue to expand and to provide useful insights into human life.