 Despite this murkiness, all three of these versions are “substantive” definitions of religion because they determine membership in the category in terms of the presence of a belief in a distinctive kind of reality. In the twentieth century, however, one sees the emergence of an importantly different approach: a definition that drops the substantive element and instead defines the concept religion in terms of a distinctive role that a form of life can play in one’s life—that is, a “functional” definition. One sees a functional approach in Emile Durkheim (1912), who defines religion as whatever system of practices unite a number of people into a single moral community (whether or not those practices involve belief in any unusual realities). Durkheim’s definition turns on the social function of creating solidarity. One also sees a functional approach in Paul Tillich (1957), who defines religion as whatever dominant concern serves to organize a person’s values (whether or not that concern involve belief in any unusual realities). Tillich’s definition turns on the axiological function of providing orientation for a person’s life.