凡人之所苦谓之病，所以致此病者谓之因。如同一身热也，有风、有寒、有痰、有食、
有阴
虚火升，有郁怒，忧思、劳怯、虫病，此谓之因。知其因则不得专以寒凉治热病矣。盖热同
而所以致热者不同，则药亦迥异。凡病之因不同，而治各别者尽然，则一病而治法多端矣。
而病又非止一症，必有兼症焉。如身热而腹痛，则腹又为一症，而腹痛之因，又复不同，有
与身热相合者，有与身热各别者。如感寒而身热，其腹亦因寒而痛，此相合者也。如身热为
寒，其腹痛又为伤食，则各别者也。又必审其食为何食，则以何药消之。其立方之法，必切
中二者之病源而后定方，则一药而两病俱安矣。若不问其本病之所因，及兼病之何因，而徒
曰某病以某方治之，其偶中者，则投之或愈；再以治他人，则不但不愈而反增病，必自疑曰
何以治彼效而治此不效？并前此之何以愈？亦不知之，则幸中者甚少，而误治者甚多！终身治
病，而终身不悟，历症愈多而愈惑矣。
经云∶夺血者无汗，夺汗者血。血属阴，是汗多乃亡阴也。故止汗之法，必用凉心敛肺
之药
正治也。惟汗出太甚，则阴气上竭，而肾中龙雷之火随水而上。若以寒凉折之，其火愈炽，
惟用大剂参附，佐以咸降之品如童便、牡蛎之类，冷冻饮料一碗，直达下焦，引其真阳下降，则
龙雷之火反乎其位，而汗随止。此与亡阴之汗，真大相悬绝。故亡阴亡阳，其治法截然，而
转机在顷刻。当阳气之未动也，以阴药止汗。乃阳气之既动也，以阳药止汗；而龙骨、牡蛎
、黄 、五味收涩之药，则两方皆可随宜用之。医者能于亡阴亡阳之交，分其界限，则用药
无误矣。其亡阴亡阳之辨法如何？亡阴之汗，身畏热，手足温，肌热，汗亦热而味咸，口渴
喜凉饮，气粗，脉洪实，此其验也；亡阳之汗，身反恶寒，手足冷，肌凉汗冷，而味淡微粘
，口不渴，而喜热饮，气微，脉浮数而空，此其验也。至于寻常之正汗、热汗、邪汗、自汗
，又不在二者之列。此理知者绝少，即此汗之一端，而聚讼纷纷，毫无定见，误治甚多也。
What causes suffering in the human body is termed a disease (Bing, 病), and the root cause leading to this disease is termed the etiology (Yin, 因). For instance, systemic heat (Shen Re, 身热) may arise from wind (Feng, 风), cold (Han, 寒), phlegm-dampness (Tan, 痰), food stagnation (Shi, 食), deficiency fire rising due to Yin deficiency (Yin Xu Huo Sheng, 阴虚火升), emotional depression and anger (Yu Nu, 郁怒), worry and overthinking (You Si, 忧思), consumptive weakness (Lao Qie, 劳怯), or parasitic diseases (Chong Bing, 虫病); these are all referred to as "etiology." Understanding the etiology prevents one from exclusively treating heat syndromes with cold-cooling herbs. Since the manifestation of heat is similar but the underlying causes differ, the medicinal prescriptions must also be radically different. This principle applies universally: when etiologies differ, treatments must vary, resulting in multiple therapeutic approaches for a single disease entity.
Furthermore, a disease is not limited to a single symptom but often presents with concurrent symptoms (Jian Zheng, 兼症). For example, if there is systemic heat accompanied by abdominal pain, abdominal pain constitutes a separate symptom. The etiology of abdominal pain also varies: it may share the same cause as the systemic heat, or it may be distinct. If exposure to cold causes both systemic heat and abdominal pain, the etiologies are combined. However, if systemic heat is caused by cold while abdominal pain results from food injury, the etiologies are distinct. In such cases, one must carefully identify the specific type of food causing stagnation and prescribe appropriate digestive herbs. The formulation of a prescription must precisely target the pathological sources of both conditions before finalizing the formula, thereby ensuring that a single treatment resolves both ailments simultaneously. If one ignores the etiology of the primary disease and the concurrent symptoms, merely stating "disease X is treated with formula Y," occasional success might lead to temporary recovery. However, applying the same formula to others may fail to cure and instead exacerbate the condition. The physician would then doubt themselves, wondering why it worked previously but fails now, without understanding the reason for previous successes. Such lucky coincidences are rare, while misdiagnoses are frequent. One may practice medicine for a lifetime yet remain ignorant, becoming more confused as the number of cases increases.
The *Classic of Internal Medicine* (*Huangdi Neijing*, 黄帝内经) states: "Those who lose blood should not sweat; those who lose sweat should not lose blood." Blood belongs to Yin; therefore, excessive sweating indicates the collapse of Yin (Wang Yin, 亡阴). Thus, the orthodox method for stopping sweat involves using herbs that cool the Heart and astringe the Lung. However, if sweating is excessively severe, Yin Qi may exhaust upwards, causing the Dragon-Lei Fire (Long Lei Zhi Huo, 龙雷之火) within the Kidney to ascend with the fluids. Applying cold-cooling herbs to suppress this fire will only intensify it. Instead, large doses of Shen Fu Tang (Ginseng and Aconite Decoction) should be used, assisted by salty descending agents such as child's urine (Tong Bian, 童便) and Oyster Shell (Muli, 牡蛎). Drinking a bowl of chilled beverage directly reaches the Lower Jiao (Xia Jiao, 下焦), guiding the True Yang (Zhen Yang, 真阳) downward. Consequently, the Dragon-Lei Fire returns to its proper position, and sweating ceases. This approach is vastly different from the treatment of sweat associated with Yin collapse. Therefore, the therapeutic methods for Yin collapse and Yang collapse (Wang Yang, 亡阳) are截然 (jie ran, 截然 - distinct/opposite), and the turning point of the condition occurs in an instant. When Yang Qi has not yet deviated, Yin-nourishing herbs are used to stop sweat; once Yang Qi has deviated, Yang-tonifying herbs are used. Herbs with astringent properties such as Dragon Bone (Long Gu, 龙骨), Oyster Shell (Muli, 牡蛎), Scutellaria (Huang Qin, 黄芩 - inferred from context 'Huang'), and Schisandra (Wu Wei Zi, 五味子) can be appropriately included in either formula. If physicians can distinguish the boundary between Yin and Yang collapse, medication errors will be avoided. How to differentiate between Yin and Yang collapse? Sweat from Yin collapse is characterized by aversion to heat, warm hands and feet, hot skin, hot and salty-tasting sweat, thirst preferring cold drinks, coarse breathing, and a surging and solid pulse. These are the diagnostic signs. Sweat from Yang collapse is characterized by aversion to cold, cold hands and feet, cool skin, cold and faintly sticky/tasteless sweat, no thirst but preference for hot drinks, weak breath, and a floating, rapid, and empty pulse. These are the diagnostic signs. Ordinary normal sweat, heat sweat, pathogenic sweat, and spontaneous sweat do not fall into these two categories. Few people understand this principle. Regarding sweat alone, debates are rampant, lacking definitive views, leading to numerous misdiagnoses.