The study of Religion has developed into a major academic enterprise over the past half century, in response to recognition of the pervasiveness and power of religions throughout history. Its study is necessary, because it is a universal phenomenon, yet at the same time each religion is distinct and different.
Some scholars have sought a definition of Religion that will serve as the basis for an academic discipline. Such a formal definition might resemble a biological one, with the various religions classified as different species. This approach has many problems, especially for a field that attempts to be empirical. A univocal, scientific definition of religion would not be useful, since it would restrict the scope of study to only a limited range of data. Such a definition also runs the risk of becoming meaningless or even misleading, as it is possible that a particular fact might be called a religion when in fact it is not.
A polythetic approach might be more useful, in that it seeks to categorize religious facts on the basis of secondary characteristics. Such an approach can produce interesting results, and it may be possible to discover patterns that can lead to explanatory theories. The problem with this approach is that it tends to generate too many definitions and to leave the student with no clear idea of what Religion actually is.
A realist approach might seek to define Religion by its functions. This approach is usually influenced by functionalist ideas. Durkheim, for example, based his definition of Religion on the function of creating solidarity. Another example is Paul Tillich’s (1957) concept of Religion, in which he defined it as whatever dominates a person’s values and directs his or her life (though the defining characteristic does not involve belief in any unusual realities).