The Yi jing, or Classic of Changes, is one of the oldest texts in China; the Ruists revered it as the first of the Five Classics. The Yi jing, Huangdi neijing (Inner canon of Yellow Emperor), and Shanhai jing (Guideways through the mountains and seas) are generally referred to as the “three unique books of antiquity”; the latter two were composed relatively late. The Yi jing is also known as the Zhou yi (Zhou changes) or may simply be abbreviated as “Yi,” meaning “changes.” After Confucius (551–479 BCE) wrote commentaries on the Zhou yi, it became a Ruist classic, and was called Yi jing, or Classic of Changes.

The Yi jing is divided into sixty-four hexagrams (six-line figures), and each hexagram consists of four components: hexagram form, hexagram name, hexagram statement, and line statement. The Yi jing is considered the most influential work in ancient China. There are more than two-thousand works of annotations and interpretations for the Yi jing; some are divination works that analyze the hexagram images and line statements; some are works elaborating the philosophical ideas of the Yi jing. The Zhou yi includes three parts: hexagram form, hexagram statement and line statements, and commentary; each was composed in different eras. Traditionally, it was said that the hexagram forms were written by the legendary figure of early antiquity Fuxi who created the eight trigrams; King Wen of Zhou (Ji Chang, 1152–1056 BCE), in middle antiquity, is said to have composed the hexagram statement and the line statements; and finally, Confucius, in late antiquity, is credited with writing a set of ten commentaries called Shi yi (Ten wings), also known as Yi zhuan (Yi commentary). A common saying was that the Zhou yi was “composed by three sages and covers three periods of antiquity.” It was quite possible that the records of divination results formed the basis for the Zhou yi, which later evolved into a type of divination reference book. Therefore, the contents of the Zhou yi were continually added to and frequently revised. After Confucius put all the contents in order, the Zhou yi was finalized.   

Zhuan (commentaries) explain and interpret the Ruist classics. Scholars in the past all believed that there were more than two-thousand commentaries on the Zhou yi, and that the earliest one was Yi zhuan (or Shi yi). Because it was written by Confucius, it was sometimes referred to as Da zhuan (Grand Commentary). Traditionally it was regarded as part of the classics. The “Yi zhuan,” written by later scholars, are works explaining the basic texts of the Zhou yi and Confucius’s commentary. Although the Zhou yi was originally used for divination, when it circulated in the late Spring and Autumn period, Confucius revised and emended the texts, which contain a wealth of philosophy. The Zhou yi originated in primitive religion, but it also had philosophical content. These “dual identities” led, in later years, to the formation of two schools of Yi studies: the Yili (meaning and significance) school, and the Xiangshu (images and numbers) school. The Yili school emphasized exploring the philosophical content of the Zhou yi, and did not consider any other images besides the gua-hexagram and the yao-line. The emphasis of the Xiangshu school was on divination, the pursuit of the mysterious nature of the Zhou yi, and an indiscriminate exaggeration of the effect of images and numbers. Numerous studies on the images and diagrams were written in the Song dynasty (960–1279), such as Wuji tu (Diagram of the unlimited ultimate), Taiji tu (Diagram of the supreme ultimate), Xiantian bagua tu (Diagram of the anterior eight trigrams), Houtian bagua tu (Diagram of the posterior eight trigrams), He tu (Diagram of the Yellow River), and Luo shu (Diagram of the Luo River). These were extremely important to the development of the Xiangshu school. Even today, this school still has considerable influence. The development of Yi studies can be divided into five stages: pre-Qin (times before 221 BCE), Han dynasty (206 BCE–220 CE), Wei-Jin (220–420) abstruse learning, Song dynasty, and Qing dynasty (1644–1911) textual research. Studying the Zhou yi today, we should continue and carry forward Confucius’ method—we should not only learn the philosophy contained in the Zhou yi, but also use it to guide us, and to try to make as few mistakes as possible in our lives. This is what the ancients meant when they said: use the Zhou yi as a book for “making fewer mistakes.”

Confucius selected six works for the basis of his teachings: the Shi jing (Classic of songs), the Shu jing or Shang shu (Classic of documents), the Li jing (Classic of rites), the Yi jing (Classic of changes), the Yue jing (Classic of music), and the Chunqiu (Spring and autumn annals). After Confucius passed away, his disciples continued to use these texts. As the influence of Ruism expanded, the status of these six works was elevated and they were called the six classics. After the book burning of Qin Shihuang (First Emperor of Qin, 259–210BCE), the Yue jing was lost to history. Afterwards, the five remaining classics became the orthodox texts in Chinese academic circles, and the philosophy contained in the Zhou yi held a leading position in China’s intellectual circles. Since the Han dynasty, the Yi jing was formally established as the first of the Ruist classics.  

In the history of Chinese scholarship, the Zhou yi is the only ancient work that combines both a system of symbols and text. Later, Ruist as well as Daoist scholars both revered this work as a classic. The influence of the Zhou yi was not confined to China, it circulated widely overseas as well. The introduction of the Zhou Yi to Europe had a tremendous effect among academic circles. The German philosopher Georg Wilhelm Friedrich Hegel (1770–1831) praised the work saying that it “represented Chinese intelligence.” Furthermore, Gottfried Wilhelm Leibniz (1646–1716), a natural scientist, mathematician, and philosopher, considered the system of the Zhou yi’s “eight-trigrams” compatible with the binary system that he invented.