"Taixuan" and Yang Xiong: The Pinnacle of Philosophical Cosmology in the Han Dynasty

Brief Introduction

"Taixuan" (The Great Mystery) is a major philosophical work composed by Yang Xiong (styled Ziyun), a prominent thinker of the Western Han Dynasty. Although the "Book of Changes" (Zhouyi) held the position of the chief classic among the Five Classics during the Han period, Yang Xiong felt that its underlying principles had not been fully exhausted. Consequently, he modeled his work after the structure of the "Book of Changes," using "Xuan" (Mystery/Profound) as its core concept to construct a more grandiose and precise system of cosmological ontology and epistemology. The "Biography of Yang Xiong" in the "Book of Han" (Hanshu) details the background of this composition and the evolution of his thought, positioning "Taixuan" as one of the most original philosophical texts in the Han era, distinct from traditional exegesis.

Core Concepts

1. The Ontological Significance of "Xuan"

The concept of "Xuan" proposed by Yang Xiong does not merely refer to a color or simple obscurity; rather, it is viewed as the source and ultimate reality of heaven, earth, and all things. He stated, "Xuan is the limit of the profound and subtle, the source of the deep and minute." He believed that the universe, evolving from formlessness to form and from chaos to order, originates from the self-transformation of "Xuan." This idea transcended the naturalism of pre-Qin Daoism, carrying strong elements of mathematical and structural construction.

2. Unique Mathematical Structure

Unlike the sixty-four hexagrams of the "Book of Changes," Yang Xiong designed a structure of "81 Hexagrams." He divided cosmic time into "three phases" (day, night, and twilight) and layers such as "Correct," "Middle," "Subtle," and "Obscure," with each of the 81 hexagrams corresponding to specific temporal units. Through this rigorous numerical deduction, he unified yin-yang, the Five Elements, the calendar, and even ethics into a single mathematical model, attempting to explain natural laws and social order through mathematics.

3. Ethical View of Correspondence Between Heaven and Humanity

"Taixuan" emphasizes "deducing heaven, earth, yin, and yang through numbers," correlating human behavior with cosmic rhythms. Yang Xiong advocated conforming to the "Way of Heaven" by cultivating virtue to align with the laws of "Xuan." This reflects the typical Han dynasty thinking of "correspondence between heaven and humanity," yet it possesses greater rationality and logic compared to the divination-based theories of Dong Zhongshu.

Connection with the Content of the "Book of Han"

In the "Bi-bibliography" (Yiwen Zhi) of the "Book of Han," while "Taixuan" was not listed as an independent classic, it occupied an important position in the categories of philosophy and calendrical science, reflecting the Han dynasty's pursuit of cosmic unity within its knowledge system. The "Biography of Yang Xiong" records that in his later years, Yang Xiong devoted himself to writing "Taixuan." When his friend Hou Ba asked him, "Do you not prefer to write something else?" Yang Xiong replied, "What I write is all about 'Xuan'." This dialogue highlights the central position of "Taixuan" within Yang Xiong's philosophical system.

Furthermore, the "Book of Han" records that because "Taixuan" was not accepted by the mainstream exegetical community at the time, it was initially discarded. However, it was precisely this "out-of-place" independent exploration that made "Taixuan" the most systematic and scientifically spirited work in Han philosophy, exerting a profound influence on later Daoist cosmology and the "Li and Qi" (Principle and Material Force) theory of the Song and Ming Neo-Confucianism.

Conclusion

"Taixuan" is not only the crystallization of Yang Xiong's personal thoughts but also a significant milestone in the transition of Han philosophy from exegesis to metaphysics. By employing the method of "deducing the yin-yang of heaven and earth through mathematics," it provides a unique perspective for understanding the cosmology of ancient China, warranting in-depth exploration in modern knowledge retrieval and philosophical research.