The Wuzhen Pian 悟真篇

The so-called Neidan (inner alchemy) is relative to Waidan (outer alchemy). Neidan takes the essence, qi (vital energy), and spirit of the human body as the "three supreme elixirs". Through the practice of specific methods and several transformations, it is condensed and formed. The function of this inner alchemy lies in prolonging life, and even achieving "immortality and becoming a true Taoist by attaining the Dao".

The study of Neidan originated with Wei Boyang in the Han Dynasty, and was further developed by Zhong Liquan, Lü Dongbin, etc. in the Tang Dynasty. From the Tang and Song dynasties onwards, it became increasingly prevalent and formed a grand spectacle. In the Song Dynasty, Zhang Boduan inherited the theories of Zhong and Lü, followed the teachings of Huangdi and Laozi, imitated Zhouyi Cantongqi (The Unity of the Three: A Commentary on the I Ching), and wrote Wuzhen Pian (The Awakening to Truth), after which the study of Neidan became widely known in the world. Siku Quanshu Zongmu Tiyao (General Catalogue of the Complete Library of the Four Treasuries) states: "This book specifically clarifies the essentials of golden alchemy, and together with Wei Boyang's Cantongqi, it is regarded by Taoists as the orthodox school."

The important contribution of Wuzhen Pian lies in its development and creation of the theory of Taoist alchemy cultivation. Wuzhen Pian developed and expressed Laozi's theory of the origin of the Great Dao - "The Dao gives birth to the One; the One gives birth to the Two; the Two gives birth to the Three; the Three gives birth to all things" - into a cultivation model: "The Dao generates one qi from the emptiness and primality; from this one qi, yin and yang are produced; yin and yang then combine to form the three bodies; from the three bodies, all things flourish". It particularly emphasizes true lead (i.e., the innate genuine primary qi).

This theory clearly reflects the alchemists' focus on the Dao of pure yang and continuous generation. Meanwhile, the theory of taking true lead as the medicine to cultivate golden alchemy is a specific application of the thought of "seizing the opportunity" in Yinfu Jing (The Scripture of Hidden Contracts). The cultivation theories such as the reversal of the five elements and the integration of the three and five into one directly inherit Zhouyi Cantongqi.

The alchemical thoughts in Wuzhen Pian, such as the innate primary qi, were inherited and carried forward by many alchemists such as Weng Baoguang, Long Meizi, Zhao Youqin, Chen Zhixu, and Liu Yiming, and also had a significant impact on Bai Yuchan's alchemical theory.

There are many misunderstandings and fabrications about the alchemy cultivation theory of Wuzhen Pian in later generations. For example, some people tried to interpret the alchemy method in Wuzhen Pian by forced analogy with the cultivation theory of refining essence into qi, refining qi into spirit, and refining spirit to return to emptiness, which caused great confusion. In fact, the alchemy method in Wuzhen Pian has nothing to do with the cultivation theory of essence, qi, and spirit. Another example is that Qinghua Miwen (Secret Writings of the Green Flower) is a work falsely attributed to Zhang Boduan, and the alchemy method described in it is quite different from that in Wuzhen Pian. However, foolish people, failing to discern this, used the cultivation theory in Qinghua Miwen as a commentary on Wuzhen Pian, which is extremely far-fetched and laughable to the learned.