Yei'Bi'Chei - Navajo religion combines moral, philosophical & preventive medicine set forth in legends & ceremonies where Man is a central theme & paramount in the Navajo world, with the sun, moon, stars, animals, plants, ceremonial knowledge, and all the rest of nature created for his use & benefit. His constant purpose of life is to control his environment by observing various taboos & by avoiding or overcoming disease, misfortune, or evil through the proper exercise of a prescribed ceremony.