One of the fundamental concepts of the Aztec religion was the grouping of all beings according to the four cardinal points of the compass and the central direction, or up and down. Therefore, in the Mexican mind the numbers 4 and 5 are very important, just as in Occidental magic the number 3 is significant.

The divine pair represented the central direction, or up and down, that is, the heaven and the earth, while their four sons were assigned to the four directions, or the four cardinal points of the compass. For that reason, three of them were characterized by different colors: red, black, and blue, corresponding to the East, the North, and the South, respectively, while Quetzalcoatl occupied the place that a white Tezcatlipoca, corresponding to the West, must have held in the primitive myth.

In fact, in the Codex Bologna or Cospiano (A pre-Columbian codex now in the library of the University of Bologna, Italy.) there appears a white Tezcatlipoca with all the characteristics of the god of providence, from whom he differs only in color. The Codex Bologna belongs to the same Puebla-Tlaxcaltecan region as the Codex Borgia, mentioned in the previous section, and these manuscripts are painted in a style identical to that of the paintings which decorate the altars of Tizatlan in Tlaxcala, and of the polychrome ceramics that are found there and in many other sites in the Valley of Puebla, such as Tepeaca, Atlixco, and Totimihuacan. All of this demonstrates that the codices or pictorial manuscripts which have been correctly designated as the Borgia group belong to the cultures that flourished in the areas around Puebla and Tlaxcala.

This fundamental idea of the four cardinal points of the compass and the central direction, up and down, which made the fifth or central region, is found in all the religious manifestations of the Aztecs and is without doubt one of the concepts they inherited from the old cultures of Mesoamerica.

Not only were colors and gods grouped in this manner. Also animals, trees, days, and men, according to the day on which they were born, belonged to one of the four regions of the world. Man was given the name of the day of his birth within the ritual calendar of 260 days, which will be explained later. The calendar was divided into four parts of 65 days each, one part corresponding to the East, one to the North, one to the West, and one to the South, and these parts were repeated an infinite number of times.