This saying comes from The Book of Changes. “The alternation of yin and yang”indicates the existence of both yin and yang, a pair of opposites that lie in all things between heaven and earth, including human affairs. Their alternation and interaction lead to the changes of things. Such changes so caused are called the Way. Furthermore, the sixty-four hexagrams in The Book of Changes symbolize all things between heaven and earth and embody the Way of the alternation of yin and yang through combination of the two yaos (the unbroken line standing for yang and the broken line for yin).

The alternation of yin and yang constitutes the Way. It is good to follow the Way. And it is in man’s nature to work by the Way. (The Book of Changes)