Any change in religious practice, organization, or belief is religious innovation. The major world religions such as Islam and Christianity have developed orthodox bodies of belief, custom, and practice, which are regarded as part of a sacred tradition. Religious innovation is thus seen as a departure from orthodoxy, because it is a threat to tradition. Since religious innovation is inevitable, there is a permanent tension between belief in the unchanging nature of orthodox tradition, and the actual social change of religious organizations. See also schism.