the four council members. Provincial administration Traditionally, provinces and altepetl were governed by hereditary tlatoani. As the empire grew, the system evolved further and some tlatoani were replaced by other officials. The other officials had similar authority to tlatoani. As has already been mentioned, directly appointed stewards (singular , plural ) were sometimes imposed on altepetl instead of the selection of provincial nobility to the same position of tlatoani. At the height of empire, the organization of the state into tributary and strategic provinces saw an elaboration of this system. The 38 tributary provinces fell under the supervision of high stewards, or , whose authority extended over the lower-ranking calpixque. These calpixque and huecalpixque were essentially managers of the provincial tribute system which was overseen and coordinated in the paramount capital of Tenochtitlan not by the , but rather by a separate position altogether: the . On the occasion that a recently conquered altepetl was seen as particularly restive, the Nahuas placed a military governor, or , at the head of provincial supervision. During his reign, Moctezuma I elaborated the calpixque system, with two calpixque assigned per tributary province. The province itself stationed one, perhaps for supervising the collection of tribute, and the other in Tenochtitlan, perhaps for supervising storage of tribute. Commoners drew the tribute, the , and distributed to the nobility, be they 'kings' (), lesser rulers (), or provincial nobility (). The Nahuas supervised the tribute collection by the above officials and relied upon the coercive power of the Aztec military, but also upon the cooperation of the (the local nobility who were themselves exempt from and recipient to tribute) and the hereditary class of merchants known as . These pochteca had various gradations of ranks which granted them certain trading rights and so were not necessarily pipiltin themselves, yet they played an important role in both the growth and administration of the Aztec tributary system nonetheless. The pochteca strongly tied their power, political and economic, to the political and military power of the Aztec nobility and state. In addition to serving as diplomats (, or "travelers of the lord") and spies in the prelude to conquest, higher-ranking pochteca also served as judges in market plazas and were to certain degree autonomous corporate groups, having administrative duties within their own estate. Ideology and state Nahua metaphysics centers around , "a single, dynamic, vivifying, eternally self-generating and self-regenerating