It is evident to anyone who is at all familiar with the documents and witnesses of the times that Aztec society at the time of the discovery of Mexico appears to be intensely religious, that all public and private life was invaded, so to speak, by rites and dominated by beliefs. But what exactly was the place of religion and its ministrants in the hierarchy of powers? To what degree was the priestly function interwoven with that of government and the administration of the city? Can the regime of ancient Mexico be described as a theocracy? To answer these questions, it is of no small use, first, to go back to the period preceding the foundation of Mexico-Tenochtitlan.