Sanctuaries and ritual traditions commonly gained prestige through claims of antiquity; conversely, novelty was an accusation occasionally leveled against groups such as the Christians. Yet ritual geography and practices were, in practice, always liable to revision, and it is evident that certain gods, holy places, and rituals had precise historical origins. How was change introduced, managed, and understood in the ancient Mediterranean world? Several varieties of innovation can be differentiated: (1) Many city-states had defined procedures for introducing new gods and initiating new collective rituals: those procedures were often envisaged as involving the active participation of the gods, as instigators or approvers of change. As in all religious systems balances were to be struck between existing religious authority, wherever vested, and the prophets, priests, and others who gained from the change; (2) Another variety of innovation represented homeostatic reactions to other changes, such as the foundations of cities, disasters survived, the fall or rise of monarchies, and the like; (3) Potentially most disruptive were those innovations brought by migration and/or the transfer of ideas and rituals across the connected Mediterranean world. The spread of mystery religions, of astrology, and of new gods provide examples of this. Certain societies were more receptive than others to this kind of novelty. Religious innovations of the first two kinds were often assimilated into the loosely bounded ritual systems of antiquity, but other changes had a cumulative effect that changes the religious geography permanently.