Religion is a unified system of beliefs and feelings that gives its followers something to believe in, someone or something sacred to worship, and a code of moral conduct. It also deals with the supernatural or spiritual, about forces and powers that are outside the control of human beings. For some people, these beliefs and feelings are a source of comfort and stability, giving them hope for the future and a sense of purpose in life. They may help them deal with death and other difficulties, or they can provide a framework for community cohesion and social welfare.
Most definitions of religion, however, do not rely on belief in an unusual kind of reality. Instead, they rely on a distinctive function that a form of religion serves, what we might call a functional definition. For example, Emile Durkheim defined religion as whatever systems of practices unite a group of people into a moral community (whether or not they involve belief in any unusual realities). One can find a similar functional approach in Paul Tillich’s definition, which turns on the axiological function of organizing a person’s values.
Some philosophers, like Rodney Needham, have taken a polythetic approach to defining religion, arguing that there are multiple properties that a practice might possess, and that it is not clear how many of these characteristics a practice must have in order to qualify as a religion. Others, such as J. Z. Smith, argue that it is possible to apply the methods of scientific inquiry to the study of religion, e.g., by putting religious forms through a process of sorting and cluster analysis much as scientists might do with the properties of bacterial strains.