The I Ching has served for thousands of years as a philosophical taxonomy of the universe, a guide to an ethical life, a manual for rulers, and an oracle of one’s personal future and the future of the state. It was an organizing principle or authoritative proof for literary and arts criticism, cartography, medicine, and many of the sciences, and it generated endless Confucian, Taoist, Buddhist, and, later, even Christian commentaries, and competing schools of thought within those traditions. In China and in East Asia, it has been by far the most consulted of all books, in the belief that it can explain everything. In the West, it has been known for over three hundred years and, since the 1950s, is surely the most popularly recognized Chinese book. With its seeming infinitude of applications and interpretations, there has never been a book quite like it anywhere. It is the center of a vast whirlwind of writings and practices, but is itself a void, or perhaps a continually shifting cloud, for most of the crucial words of the I Ching have no fixed meaning.

The origin of the text is, as might be expected, obscure. In the mythological version, the culture hero Fu Xi, a dragon or a snake with a human face, studied the patterns of nature in the sky and on the earth: the markings on birds, rocks, and animals, the movement of clouds, the arrangement of the stars. He discovered that everything could be reduced to eight trigrams, each composed of three stacked solid or broken lines, reflecting the yin and yang, the duality that drives the universe. The trigrams themselves represented, respectively, heaven, a lake, fire, thunder, wind, water, a mountain, and earth (see illustration below).