Religion is the range of human beings’ relations to that which they regard as holy, sacred, absolute, spiritual, divine or worthy of especial reverence. It is also seen as people’s way of dealing with their ultimate concerns about life and death. These concerns may be expressed in traditional terms of relationships with and attitudes toward gods or spirits; in more secular or naturalistic religions, they are often expressed in terms of one’s relationship to the broader human community or the natural world.

In the nineteenth century, increasing exploration of non-European religions sparked a re-examination of the nature of religious phenomenon. The work of Johann Gottfried von Herder (1744-1803), who promoted an evolutionary account of humanity and took a positive approach to mythology, and the French historian Édouard Quinet (1830-89), who used his knowledge of Indian religion to promote a study of the ‘Genie des religions’ (the Genie of Religions), opened the way for a more empirical approach to the nature of religious belief and practice.

The development of sociobiological theory since the early twentieth century has led to a major shift in the definition of religion. This shift has been from a substantive approach that defines membership in religion in terms of belief in a distinctive kind of reality, to functional approaches that define religion in terms of the function it serves in people’s lives. The result of this shift has been that what is counted as religion by a functional definition is often not considered to be a religion by other definitions.