Yitongbian 易通變

Yitongbian 易通變, also called Huangji jingshi tongbian 皇極經世通變 or Tongbian 通變 for short, is a book on divination written during the Southern Song period 南宋 (1127-1279) by Zhang Xingcheng 張行成 (jinshi degree 1132), courtesy name Wenrao 文饒 or Zirao 子饒, from Linqiong 臨邛, Sichuan. Zhang wrote a total of seven books serving as explanations to the divination classic Yijing 易經 "Book of Changes" and books related to prognostication. This collection, called Yishuo qi zhong 易說七種, includes Zhouyi shuyan 周易述衍, Yixuan 翼玄, Yuanbao shu zongyi 元包數總義, Qianxu yanyi 潛虛衍義, Huangji jingshi suoyin 皇極經世索隱, Guanwu waipian yanyi 觀物外篇衍義, and Yitongbian. Some of these books refer to Shao Yong's 邵雍 (1011-1077) Huangji jingshi shu 皇極經世書, which holds that the principles of change and growth of all things in heaven and earth can be prognosticated from aspects of time.

Zhang stands in the tradition of Chen Tuan 陳摶 (871–989) and Shao Yong by using "symbols and figures of Anterior Heaven" (xiantian xiangshu 先天象數). Zhang Xingcheng selected fourteen diagrams related to hexagram numbers (guashu 卦數) and organized, interpreted, and explained them to elucidate the transformations (bian 變) of hexagrams and transgressions of related situations.

In the study of the Zhouyi 周易 (i.e., the core part of the Yjing) by Han-period 漢 (206 BCE-220 CE) scholars, there were three traditions. The first, the School of Master Meng (Mengshi xue 孟氏學), was founded by Meng Xi 孟喜 (1st cent. BCE), a supporter of the New-Text Tradition of the Yijing. He allocated the 64 hexagrams according to periods of time (qihou 氣候; hou 候 being five-day periods, and qi 氣 periods of fifteen days) and interpreted the Classic in terms of hexagrams ruling over periods of time (guaqi 卦氣). He thus advocated the division of hexagram-related time into periods of 6 and ⁷/₈₀ days (liuri qifen 六日七分). The second school, the Teachings of Master Jing (Jingshi xue 京氏學), was initiated by Jing Fang 京房 (77-37 BCE), also a proponent of the New-Text Tradition. He focused on explaining and predicting disasters and anomalies by using the techniques of "flying and hiding" (fei fu 飛伏) and "matching the Celestial Stems" (na jia 納甲), i.e., relating the eight hexagrams to the Five Agents (wuxing 五行). Fei Zhi 費直 finally, who established "Master Fei's Studies" (Feishi xue 費氏學), belonged to the Old-Text Tradition. He utilised the Ten Wings (Shiyi 十翼; commentaries on the Zhouyi) to explain the Classic's text and discussed the principles of superimposition (cheng 乘), succession (cheng 承), comparison (bi 比), and response (ying 應). In the Later Han period 後漢 (25-220 CE), Wei Boyang 魏伯陽 (151-221) developed the system of the Zhouyi cantong qi 周易參同契, which makes use of alchemical formulas (danjue 丹訣). He was the first to discuss the positions of the Heavenly stems jia 甲, ren 壬, yi 乙, and gui 癸.

In the Northern Song period 北宋 (960-1126), Chen Tuan invented the "Pre-heaven diagram" (Xiantian Tu 先天圖), which was later passed down through Mu Xiu 穆修 (979–1032) to Shao Yong. They proposed the theory of Pre-heaven and Post-heaven (xiantian houtian 先天後天), which discerns between conditions before birth or the creation of the world and such after birth or the creation of the world, respectively. This theory became widely circulated. Therefore, after the Southern Song period, scholars who explained the Yijing through numbers regarded Chen Tuan and Shao Yong as their founding fathers. However, since Chen Tuan followed Daoist teachings, Confucian scholars tended to cast Chen Tuan aside and only referred to Shao Yong.

Zhang Xingcheng obtained the fourteen diagrams passed down by Shao Yong while residing in Sichuan and compiled the theory about them into this book. According to Zhang's preface, Shao Yong’s teachings focused on two diagrams or symbols, namely Jiaotai 交泰 "Interaction [of Heaven and Earth] in Harmony" and Jiji ䷾ 既濟 "Completion". These two diagrams were further based on hexagram periods (gua qi), with the intertwining of the numbers three and five being used to explore them.

Zhang Xingcheng believed that these diagrams expressed the rise and fall of cycles in the world, as well as people's prosperity and decline. For example, he stated that even the functioning of a person's five internal organs could be deduced through the numerical principles of the Yijing. However, his interpretations were not without forced connections and arbitrary associations. Later scholars had thus mixed opinions about this book. Li Xinchuan 李心傳 (1167-1243) criticised it for being overly contrived, while Zhu Bi 祝泌 praised it for containing many original insights. Some scholars also believed that the book had too many digressions. Nevertheless, Zhang Xingcheng's theories had their own internal logic and coherence, making his work an invaluable reference for later scholars studying Yijing theories from the Song period.

The text is found in the series Siku quanshu 四庫全書 and Siku quanshu zhenben 四庫全書珍本.