Religion is a broad category of human behavior with many overlapping features. It can encompass anything from worship and belief in a god or gods to mystical experiences and the practice of magic. It can also include beliefs and behaviors that are not based on any gods but which a person believes provide meaning to their lives, such as the practice of tai chi or yoga. It can even encompass a belief in the possibility of life after death. The variety of practices that can be described as religious is so great that it is not surprising that scholars and other commentators have struggled with how to define the concept.
One question is whether a definition should be functional, focusing on the kinds of functions that can be derived from religions, or substantive, focusing on the conceptions that people hold of religion. A functional approach has the advantage of making it possible to treat religion as something that occurs in all cultures. However, it is sometimes argued that it does not allow one to understand why and how a particular kind of religion developed.
A substantive approach, on the other hand, may be more appropriate for a social science study of religion. In this view, the characteristics of religion that make it different from other cultural forms are those that the adherents themselves believe are necessary for their own spiritual well-being and that they think will benefit society. In this view, the social context of a religion is less important than its conception of reality.
The definitions that scholars have used to describe religion vary widely, from a broad approach encompassing any belief in spirit beings or in the existence of gods or spirits to one narrowly defined as the belief in a transcendental creator. A number of scholars have also tried to develop a social taxonomy for religion by listing the characteristics that they think are necessary for a religion. These taxonomies can be useful in sorting out the many religious practices.
In addition to a taxonomy, other issues related to the concept of religion that have been debated by scholars include how to determine what is and is not religious, how to count religiosity, and when it makes sense to use the word religion. Some scholars have criticized the use of the term for its association with imperialist and neocolonialist projects. Others have argued that the emergence of a social taxonomy for religion is an inevitable consequence of the development of language to describe social phenomena.
A final issue is the extent to which it is possible to develop a scientific theory about religion. Some have argued that a science of religion is impossible because it involves hidden mental states and cannot be observed directly. Other researchers have argued that the problems of studying these mental states are not insuperable. They have pointed to experiments in which the brain activity of participants who were experiencing religious experiences was recorded by magnetic resonance imaging. These studies have demonstrated that religious people show heightened levels of neurotransmitters associated with the brain’s reward system. They have also cited studies of the effects of prayer on medical conditions and in which participants reported increased wellbeing following participation in religious services.