Astronomy and Chen Zhixu’s Neidan Theory

Chen Zhixu (陳致虛), a prominent Taoist master of the Yuan Dynasty, significantly contributed to aspects such as the creation of Taoist genealogy and the theoretical interpretation of Neidan (内丹 internal alchemy studies). Astronomy of different aspects served as an important intellectual resource for him. Chen Zhixu not only explained the correlative cosmological model in traditional internal alchemy theories, but also introduced systematic calendrical knowledge to broaden the astronomical foundation of his theoretical propositions, thereby strengthening the connection between internal alchemy practices and astronomical research. The model of the cosmic structure based on the Hun Tian theory (渾天說 the Spherical Heaven Theory, a major ancient Chinese cosmological theory that regards the sky as a sphere and encloses the earth in it) that he constructed is not merely a correlative illustration but also laid a solid mathematical foundation for his theoretical system. Nonetheless, Chen Zhixu’s methodological exposition of the hierarchy between internal alchemy practices and astronomical research reveals that his application of astronomical knowledge was selective and ultimately subordinated to, and constrained by, his Taoist transcendental goals. Therefore, Chen Zhixu’s work, to some extent, reveals a structured relationship between Taoism cultivation practices and ancient Chinese science.