I have often pondered the renowned physicians of past dynasties who could restore life to the dead and cure diseases by dispelling pathogenic factors. This was not because they were born with such knowledge, but rather because they followed and elaborated upon the classics of former sages. With superior talent and profound insight, they explored subtle details and sought hidden principles, studying the underlying theories until they grasped their essential meaning. Thus, they were capable of handling any situation effectively. Moreover, among all diseases, none is more urgent than *Shanghan* (Cold Damage Syndrome). The outcome—either death or recovery—is often determined within six or seven days; if it persists beyond ten days, the prognosis becomes even more critical. Therefore, Zhang Zhongjing (the Grand Administrator of Changsha) of the Han Dynasty, lamenting the loss of lives in the past and mourning those who died prematurely without hope of rescue, composed several volumes of *Shanghan Lun* (Treatise on Cold Damage). It contains 397 therapeutic methods and 113 prescriptions, serving as the standard for medical practice and the fundamental basis for treating diseases.

However, from the Han Dynasty to the present day, over a thousand years have passed. Only Wang Shuhe truly grasped its essential meaning, while later practitioners failed to find the right approach. Consequently, there were few annotations and lectures on this subject during that period. Since the Song Dynasty, some famous physicians have produced writings, such as Pang Anchang’s *Subing Lun* (Treatise on Sudden Illnesses), Zhu Gong’s *Huo Ren Shu* (Book on Saving Lives), Han Zhihe’s *Weizhi* (Subtle Principles), and Wang Shi’s *Zhengzhi* (Diagnosis and Treatment). Although these works mutually elucidate certain principles, none fully reveals the profound intent of Zhang Zhongjing.

Cheng Wuji, a scholar from Liaoshe, came from a family of Confucian physicians. He was intelligent, quick-witted, and possessed extensive memory. In his work *Shanghan Mingli Lun* (Clarifying the Theory of Cold Damage), he presented insights previously unexplored by earlier authors. He established diagnostic frameworks, differentiated pathological forms, and analyzed syndromes. He clarified conditions that appeared similar but were actually distinct, and辨析 (distinguished) those that seemed correct but were misleading. He explained that chills and tremors can be diagnosed internally or externally, and discussed how irritability and restlessness differ between Yin and Yang patterns. He enabled practitioners to clearly discern deficiency and excess through delirious speech (*Zhenyu*) versus feeble voice (*Zhengsheng*), and to distinguish the depth and severity of cold extremities (*Sini*) from true cold limbs (*Jue*). Starting with fever and ending with relapse due to overexertion (*Laofu*), the book comprises fifty chapters and is titled *Mingli Lun*. This truly captures the essence of Master Zhang’s teachings. It allows students of medicine to understand the principles through reading, recognize syndromes to differentiate diseases, and achieve clarity of mind free from confusion. Is this not a profound contribution?

My family has practiced medicine for fifty years. I have thoroughly investigated core principles and studied classics from childhood to old age, browsing both ancient and modern medical texts. Seeing the clear and brilliant theory in this book, I could not remain silent. Therefore, I have written this preface to briefly outline its significance.

On the fifteenth day of the eighth month in the Renxu year, Yan Qizhi of Jinshan wrote this preface.