I Ching

The mechanism is simple and the elaboration on top of it is enormous. A line is either unbroken, associated with yang, or broken, associated with yin. Three lines make a trigram, and there are eight of them, conventionally glossed as heaven, earth, thunder, water, mountain, wind, fire and lake. Stack two trigrams and you have a hexagram of six lines; there are sixty-four, which exhausts the possibilities.

Each hexagram carries a name, a short judgement, and six line statements read from the bottom up. The language of the oldest layer is compressed and often opaque: omens, fragments of ritual, snatches of what appear to be old rhymes, verdicts such as auspicious or no blame, and images of crossing the great water or seeing the great man. Some line statements plainly record concrete historical or agricultural situations whose original reference is lost.

Around this core sit the Ten Wings, appendices that turn the manual into a philosophy. The Commentary on the Judgements and the Commentary on the Images explain each hexagram in ethical and cosmological terms. The Great Commentary, the most quoted of them, argues that the changes of the lines model the changes of the world, that heaven and earth generate the myriad things through the interaction of yin and yang, and that the sage who understands the pattern can act in accord with it. It is in the Wings, not the core, that the book acquires the metaphysics later readers came for.

A consultation yields not only a hexagram but often a second one, since lines identified as changing turn into their opposites. The reading lies in the movement between the two figures, which is what the title means.

The layers are of quite different ages and this is not seriously disputed. The core, the Zhouyi, belongs to the Western Zhou and is usually placed around the ninth century BCE; its language, its references and its assumptions about divination all point there, and it stands at a considerable distance from the classical Chinese of the Warring States. Tradition assigns the hexagram statements to King Wen, composing in prison, and the line statements to his son the Duke of Zhou. Scholars treat these attributions as legendary and the core as accumulated diviners' record.

The Ten Wings were traditionally ascribed to Confucius. The Analects mentions the Changes only glancingly, the philosophical vocabulary of the Wings is later than his lifetime, and the consensus dates them across the Warring States and into the Han, several centuries after his death in 479 BCE. Some traditional scholars, notably Ouyang Xiu in the eleventh century, had already doubted the attribution on internal grounds.

The book owes its survival partly to being useful. When the Qin proscribed the classics in 213 BCE, the Records of the Grand Historian says works on divination, medicine and agriculture were exempt. The Changes was a working manual and passed through untouched, where the Book of Documents did not.

Manuscript evidence confirms that the text was still fluid. The silk Mawangdui copy of 168 BCE has the hexagrams in a completely different sequence from the received order, organised systematically by upper trigram, and carries commentarial material not in the standard Ten Wings, including dialogues attributed to Confucius that the received tradition never had.

The classical procedure uses fifty dried yarrow stalks. One is set aside; the rest are divided, counted out in fours and set between the fingers through three operations that produce one line, and the whole is repeated six times. The arithmetic is designed so that the four possible outcomes are not equally likely. The simpler three-coin method, which spread from the Song dynasty onwards, tosses three coins six times and is much faster, but it flattens those probabilities, so the two methods do not give identical odds of a changing line. Practitioners argue about whether this matters.

Interpretation was never left to the diviner alone. Commentaries multiplied: Wang Bi in the third century, who read the hexagrams as situations rather than omens; the Song Neo-Confucians, for whom Zhu Xi insisted the book be understood first as a divination manual and only then as philosophy; and the numerological tradition of Shao Yong, whose arrangement of the sixty-four figures caught Leibniz's attention in 1703 as a representation of binary arithmetic.

The route into modern Western reading runs through one edition. Richard Wilhelm, a German missionary in Qingdao, translated the book into German in 1924 with the help of the scholar Lao Naixuan, presenting it through the Neo-Confucian commentarial tradition he had been taught. Cary Baynes rendered Wilhelm's German into English, published in 1950 in the Bollingen Series, with a foreword by Carl Jung that used the book to introduce his notion of synchronicity, meaningful coincidence not explained by cause and effect. That foreword, more than the translation, made the book a fixture of Western counterculture from the 1950s onwards, and it means many English readers meet a Chinese classic at two removes and framed by a Swiss psychiatrist.