At the time of the Spanish Conquest, the religion of the Aztecs was polytheistic, based on the worship of a multitude of personal gods, most of them with well-defined attributes. Nevertheless, magic and the idea of certain impersonal and occult forces played an important role among the people. There was, in addition, among the uneducated classes, a tendency to exaggerate polytheism by conceiving of as gods, also, what, to the priests, were only manifestations or attributes of one god. Today, in a like manner, images of a saint are sometimes considered not only different but antagonistic, in spite of the fact that the Roman Catholic priest explains that the images are only two different aspects of the same saint.

But if there was a magic and impersonal background in the religion of the Aztec people, as well as an exaggerated polytheism, there is also evidence of the efforts of the Aztec priests to reduce the multiple divinities to different aspects of the same god, for when they adopted the gods of conquered peoples or received gods from peoples of more advanced culture, the priests always tried to incorporate them, as did the Romans, into their own national pantheon, by considering them as diverse manifestations of the gods they had inherited from the great civilizations which preceded them and from which they had derived their culture.

Thus it was, for example, that the god of wine was doubtless for the Mexican priests a single god, called Ometochtli because of his calendar name, which means "Two Rabbit." Nevertheless, in the manuscript known as the Codex Magliabecchiano (A post-Columbian Mexican codex in the National Library, Florence, Italy) we find a great many gods of pulque, with the characteristics of the region whence they came and names derived from those same areas. Thus we have the famous Tepoztecatl—or "he of the copper ax," who was the god of Tepoztlan, Morelos—as well as Toltecatl, the god of Tula, and Yautecatl, the god of Yautepec.

While the Aztec priests tried to unite in a single concept the different gods of the different tribes and synthesize in a single power what were considered different gods, the people as a whole would not admit that their local god was subject to any other or that he was only an attribute of a superior being.

The only exceptions were Huitzilopochtli, the Aztecs' own tribal god, and the other deities associated with him in the national myths kept alive by Aztec pride. In legends of later times we see this god figuring among those who created the world, occupying a place similar to that held by the traditional Toltec and Teotihuacan gods and by those gods worshiped by the people of the Valley of Mexico before the volcano Xitle covered their homes with lava, several centuries before Christ.

However, as we shall see later, a very ancient school of philosophy held that the origin of all things was a single dual principle, masculine and feminine, that had created the gods, the world, and man. Certain exceptional men, like Nezahualcoyotl, the king of Texcoco, already preferred to worship an invisible god that could no longer be represented. He was called Tloque Nahuaque, or Ipalnemohuani, "the god of the immediate vicinity," "that one through whom all live," who was placed above the heavens and in the highest realm and on whom all things depended. If this is not a true monotheistic attitude because it still acknowledges the existence and the worship of other gods, it does indicate that in exceptional mentalities the philosophical desire for unity had already appeared and that men were seeking a single cause to explain all other causes, and a single god superior to all other gods, just as the gods were superior to all men.

Therefore, when Nezahualcoyotl built a temple in Texcoco upon a pyramid of nine terraces representing the nine heavens, he did not place in the sanctuary that crowned this pyramid any image representing the god, since "the one through whom all live" could not be portrayed and must be conceived as pure idea. Naturally this single god of Nezahualcoyotl did not have much following, nor did he affect the religious life of the people. The gods of philosophers have never been popular, for they arise from the need of a logical explanation of the universe, while the common people require less abstract gods who will satisfy their sentimental need for love and protection.