When a hexagram was still a string of numbers
The I Ching is a book of lines: six broken or unbroken strokes, sometimes a line that turns. The form is old. It is not the beginning. Numbers came before the lines, and cracks in bone came before the numbers.
Chinese sources set two terms side by side. Bǔ 卜 is the heating of a turtle shell or a shoulder blade until it splits. Shì 筮 is the counting of yarrow stalks. Together they are shīguī 蓍龟: yarrow and turtle. Chinese sources treat the two as a fixed pair.
Bone and shell at Anyang
The Shang oracle bones (jiǎgǔwén 甲骨文) are inscribed ox scapulae and turtle plastrons. They were heated until they cracked; the crack patterns were read as a forecast. Most surviving pieces date from the late Shang period, roughly 1250-1050 BCE. The earliest inscriptions, from the reign of king Wu Ding, have been placed by carbon dating around 1254-1197 BCE.
They were found near present-day Anyang in Henan, the last Shang capital. The scholar Luo Zhenyu (罗振玉) identified this site, Yinxu (殷墟), in 1908 as the source of the bones. The Zhou conquered the Shang around 1046-1045 BCE. That is about the upper bound of the classical oracle-bone practice.
According to World History Encyclopedia, that practice preceded later Zhouyi hexagram divination and at first ran alongside it. The same source dates the Zhouyi as a text to 1100 BCE at the earliest, some centuries after the oldest bones. Scholars do not agree on the date of the core Zhouyi. The traditional attribution names the 11th century BCE (king Wen and the Duke of Zhou); philological work by Gu Jiegang, Kunst, Shaughnessy and others sometimes places the compilation later, in the early to mid-Western Zhou. That argument belongs with what scholars argue about.
According to Guangming Wang (光明网), the online edition of the newspaper Guangming Ribao (光明日报), the Hongfan 洪范 chapter of the Book of Documents (尚书) says that for important decisions both turtle and yarrow were consulted, each with its own role. The same source describes a shift: under the Shang and the early Zhou the turtle was dominant; from about Han times the yarrow surpassed that method in prestige.
Guangming Wang also gives two Chinese explanations. The ancients, it says there, preferred the turtle shell in part because the plastron resists decay better than other bone, which helps explain why this material in particular has survived. The classical gloss, attributed to Confucius, reads the graph 蓍 as "old" and 龜 as "long-lived": to consult both was to ask advice of experienced elders.
It follows, we think, that the archaeological picture can lean the wrong way. Shell and ox bone remain. Yarrow stalks do not. Count only the finds and you see a world of bone. The texts speak of two practices at once.
Zhang Zhenglang and the numbers on bronze
For decades scholars puzzled over odd sequences of three or six numerals on Shang and early Zhou oracle bones and on bronze inscriptions. The historian and paleographer Zhang Zhenglang (张政烺, 15 April 1912 - 29 January 2005) recognized them as the earliest form of Yi hexagrams.
Zhang was born in Rongcheng in Shandong, graduated from the history department of Peking University in 1936, became a professor there in 1946, and from 1966 was a researcher at the Institute of History of the Chinese Academy of Sciences. In late November or early December 1978 he presented the find at a paleography conference at Jilin University in Changchun. In 1980 the article appeared in Kaogu Xuebao (考古学报, "Archaeological journal"), number 4, under a title that amounts to an attempt to explain the Yi hexagrams in early Zhou bronze inscriptions.
Zhang himself spoke of a Yi hexagram (yìguà 易卦), a divination number (shìshù 筮数), or a divination hexagram (shìguà 筮卦). The term "numerical hexagram", later common in Western scholarship, is not a term from ancient China.
What he found were sequences of three or six numerals. Odd numbers he read as yang lines, even numbers as yin lines. The sequences can then be converted into the familiar broken and unbroken lines of trigrams and hexagrams. The numerals themselves are mainly 一 (1), 五 (5), 六 (6), 七 (7), 八 (8) and 九 (9): more than the two values of the later classical line.
According to modern scholarship, including Shaughnessy in 1993, these number sequences are older than the later binary line style. On that reading the line form is a later simplification of an older number system, not the reverse. Zhang further held that the eight trigrams had already arisen in the Neolithic and the 64 hexagrams already in the Shang period. That is his thesis, not an established fact. The inscriptions found so far do not prove that dating with certainty.
Our reading: Zhang decoded the sequences by translating them into a later vocabulary, odd as yang, even as yin. The key works. It does not yet say that the makers of the inscriptions themselves already thought in yang and yin.
Four phases, and a bamboo text from Tsinghua
中国社会科学网 (China Social Sciences Net, the online platform of the Chinese Academy of Social Sciences) divides the research into four phases: a speculative period, Zhang's breakthrough from 1978, a period of rebuttal that the historian Li Xueqin (李学勤) opened around 1999, and a period of verification.
Li doubted whether all of these number groups should be read as full Yi hexagrams. He later changed his position in part, after studying the Tsinghua bamboo strips. The Department of Philosophy at Tsinghua University reports that only the 2013 publication of the Tsinghua bamboo text Shifa (筮法) confirmed that the yin-yang line symbols of the Yijing derive from specific older number forms.
According to 人民网 that Shifa runs to 63 strips, is fully intact, and is the only bamboo text recovered still in its original scroll form. It includes loose illustrations or diagrams and treats 17 kinds of question (mìng 命), against the 8 named in the later ritual handbook Zhouli (周礼). The text records 114 numerical hexagrams, built from six numerals: 一, 四, 五, 六, 八, 九.
Set those six numerals beside the Shang and early Zhou sequences, and what stands out is that both corpora have six values, but not the same six. The early inscriptions have mainly 1, 5, 6, 7, 8 and 9. The Shifa has 1, 4, 5, 6, 8 and 9: a 4, and no 7. The classical yarrow count yields a third set: 6, 7, 8 or 9. Our reading: the number vocabulary was not fixed. What later looks binary is the end of successive narrowings, not the starting point.
The Yijing scholar Ding Sixin (丁四新), a professor at Tsinghua and Peking University, published in 2022 on 儒家网, reprinted by 中国社会科学网, the claim that research on numerical hexagrams ought to come to an end (数字卦研究应当走向终结). The term itself, he argued, sows confusion and has no historical legitimacy. Tsinghua says the derivation of line from number is confirmed. Ding says the name of the paradigm would be better dropped.
Our reading: the empirical question, whether the numbers belong to the Yi, is largely settled. The naming is not. A field that argues over its own term doubts the finds less than their name and interpretation.
Yarrow and the count
The plant of the classical method is yarrow (蓍草, shīcǎo). According to a Chinese survey article it has sturdy, straight, tough stems that do not break easily even when dried. The classical counting method, described in the Great Treatise (Xìcí 系辞), one of the Ten Wings, uses 50 stalks. One is set aside, as a sign of the One or Taiji. The remaining 49 are counted and divided.
The numbers that fall from that count are 6, 7, 8 or 9. Nine is old yang: a solid line that turns to yin. Eight is young yin: a broken line, stable. Seven is young yang: a solid line, stable. Six is old yin: a broken line that turns to yang. Set that convention beside the older sequences and it is a further thinning of the range 1, 5, 6, 7, 8, 9.
Tradition places the origin of yarrow with the mythical culture hero Fu Xi (伏羲), who is said to have laid out the trigrams with stalks from a garden at his own tomb temple. Fu Xi is not a historically verifiable figure. The attribution is tradition, not evidence. The same holds for the legend of four sages who made the book in turn: Fu Xi the trigrams, king Wen and the Duke of Zhou the hexagram and line texts, Confucius the commentaries. Modern philology treats that as a legendary attribution constructed after the fact. Confucius's authorship of the Ten Wings has been rejected since the Song scholar Ouyang Xiu in the 11th century, and by virtually all modern researchers.
Thirteen consultations in the Zuozhuan
The Zuozhuan (左传), the commentary on the Spring and Autumn Annals, contains thirteen separate Zhouyi divinations, with fourteen hexagrams in all; one incident involved two consultations. The earliest case falls in the 22nd year of Duke Zhuang of Lu (庄公二十二年), 672 BCE. A Zhou court scribe consulted the Zhouyi for the ruler of Chen about his newborn son Jing Zhong (敬仲). The oracle cast hexagram Guān 觀, which changed to Pǐ 否, and predicted that not Chen itself but a later descendant through the Jiang line would rule in another land. That forecast was later read as fulfilled when Jing Zhong's descendants became the ancestors of later rulers of Qi.
According to a Chinese survey of these cases, in the 15th year of Duke Xi (僖公十五年, 645 BCE) the Zhouyi was consulted about the marriage of Boji to the ruler of Qin. Hexagram Guī Mèi 归妹 changed to Kuí 睽. The oracle predicted misfortune. According to the Zuozhuan the marriage did in fact collapse six years later in war and flight.
In the passage on that year of Duke Xi stands the formula that the turtle gives an "image", derived from the crack patterns, and the yarrow a "number". That suggests the two techniques then knowingly existed side by side, each with its own kind of result. Set that formula beside Zhang's number sequences, and what stands out is that yarrow was already a numbers practice before it became a book of lines. The image belonged to the bone; the number belonged to the stalk.
Of the thirteen cases, according to that survey, three have no moving line, one has several moving lines at once, and the remaining ten have exactly one moving line. That suggests that a single change was the early norm, and that later rules for several moving lines are an expansion. According to the same survey the themes vary: marriage, birth, succession, war, sacrifice, the moving of a court seat. On that reading the Zhouyi in the Spring and Autumn period (770-476 BCE) was an ordinary tool for practical decisions at the feudal courts.
Yin and yang, written in later
The pair yin-yang, as a philosophical name for the hexagram lines, does not appear, according to the Stanford Encyclopedia of Philosophy, in the short hexagram and line texts of the oldest Zhouyi itself. It is worked out only in the later commentary tradition of the Ten Wings, composed between the 5th and 2nd centuries BCE. The Xìcí wing is the commentary in which that cosmology is most fully tied to the lines.
Line the evidence up, and the order comes to three steps. First, number sequences with several values in the late Shang and early Zhou. Then a simplification to broken or unbroken. Only then, in the Ten Wings, the explicit coupling to yin and yang. Yin and yang are not primal terms with which the makers of the Zhouyi knowingly worked. They are a later layer of reading.
Sources
- Oracle bone, for the Shang bones, Anyang, Luo Zhenyu, and the dating down to the Zhou conquest
- Oracle Bones (World History Encyclopedia), for the overlap of bone practice and Zhouyi, and the early dating of the text
- 光明网 (Guangming Wang), for the pair bǔ/shì, the Hongfan chapter, the later rise of yarrow, and the Chinese accounts of durability and old age
- Cracking bones and numbers, for Zhang's decipherment, his own terms, and the mapping of odd and even onto lines
- 张政烺 (Zhang Zhenglang, Peking University), for his career and institutional posts
- Fudan Center for excavated texts on Zhang Zhenglang, for the 1978 Changchun conference and the 1980 Kaogu Xuebao article
- Stanford Encyclopedia of Philosophy: Chinese Philosophy of Change, for yin-yang in the Ten Wings, the legend of the four sages, and the dating debate
- The Ancient Yarrow Stalk Method, for the fifty stalks and the one set aside
- 网易 on 蓍草 (NetEase on yarrow), for the tough stems of the oracle plant and the Fu Xi tradition
- Sohu survey of Zhouyi consultations in the Zuozhuan, for the thirteen cases, Guān and Pǐ, Boji, and the count of moving lines
- Kidder Smith on the Zhouyi in the Zuozhuan (pdf), for the formula that the turtle gives an image and the yarrow a number
- 中国社会科学网 (China Social Sciences Net), for the four research phases and the reprint of Ding Sixin
- 清华大学哲学系 on 筮法 (Tsinghua University Department of Philosophy on the Shifa), for the 2013 publication, Li Xueqin, and the derivation of line from number
- 人民网 on the Tsinghua text 筮法 (People's Daily Online on the Tsinghua Shifa), for the 63 strips, the 17 question types, and the 114 number hexagrams
- 数字卦研究应当走向终结 (Numerical hexagram research ought to come to an end), for Ding Sixin's 2022 claim about the term itself
- Translation of the Xici (Adler), for the Xìcí as the fullest coupling of yin and yang to the lines
- Springer article on early Yi number sequences, for the numeral values 1, 5, 6, 7, 8 and 9 in the oldest sequences
- Hexagram (I Ching), Wikipedia, for the 6-7-8-9 convention of old yang, young yin, young yang and old yin
- Shaughnessy (1993), via academia.edu, for the claim that the number sequences are older than the later binary line style