To possess the detailed esoteric knowledge necessary to perform the religious rituals that were patronized by the upper classes in early civilizations required considerable training. In many instances such knowledge, including rituals, prayers, hymns, incantations, and divination formulae, was the prerogative of priests, who were expected to manage the technical details of human relations with the supernatural. In early civilizations or still earlier smaller-scale societies, a shaman or sorcerer might learn how to relate to the supernatural from ecstatic experiences or by seeking personal instruction from a experienced master of these arts. Most individuals became part of a corporate priesthood by receiving formal instruction in a religious school or apprenticing with a religious cult or institution.

One of the fantasies that many religious scholars have propagated concerning early civilizations is that they were characterized by struggles for power between priests and secular authorities. The extensive nineteenth-century historical literature concerning competition for political supremacy between kings and popes in medieval Europe convinced many anthropologists that such conflicts characterized most complex premodern societies (L. White 1949: 233–81). To evaluate such relations objectively, it is necessary to examine the training, lifestyle, organization, and roles of priests in specific early civilizations.

Each city-state in the Valley of Mexico had its own religious institutions, and every major deity possessed its own temple or temples. All the larger temples had their own priests (tlamacazqui), who lived in special residences adjacent to the temple while they were on duty.