尝谓长沙之论，谨严之中，皆活法也。天之气化不一，有主气，有客气；人之脏性亦不一，有阴脏，有阳脏。春温、
夏热、秋燥、冬寒，四时之定位也；厥阴风化为初之气，少阴热化为二之气，少阳火化为三之气，太阴湿化为四之气，
阳明燥化为五之气，太阳寒化为终之气，六节之常度也。故寒必伤于冬，而温与热必在于春与夏，此其大较也。然而以
五运言之，则土运、金运之迁代无常，以六气言之，则司天、在泉、左间、右间之加临各别，益之以胜、复之理，太过、
不及之数，于是乎春夏亦有伤寒，隆冬非无温病，所谓非其时而有其气，不可胶于节候之常。《素问》曰∶至高之地，冬
气常在，至下之地，春气常在。《灵枢》曰∶以一日分为四时，日出为春，日中为夏，日入为秋，夜半为冬。皆是以活法
言之。说者于伤寒必主冬月，于桂枝、麻黄、三阴诸辛热剂，必主冬月之伤寒，而不可用于春夏之时，拘泥时令，于变
化之理，得毋有未备欤！《通天篇》曰，有太阴之人，少阴之人，太阳之人，少阳之人，阴阳和平之人，及夫五五二十五
人之政，《本脏篇》又言二十五变。昔夏英公有异禀，卧即身冷如僵，常服仙茅、钟乳、硫黄，莫知纪极，小吏窃食，即
发疽死。而太阳之人，则饮啖生冷而不知节，恣情房室而不加疲，此其阴阳之反，何啻天渊，是故有从化之说。从者，
大之气也；化者，脏之性也。阴脏者多寒，阳脏者多热，所谓阴从阳化，阳从阴化，热从寒化，寒从热化，亦皆以活法
言之，而尤不可泥于温凉寒燠之常也。夫以运气主客之殊，加之以脏腑阴阳之别，其病遂千态万状，而莫可穷诘。仲圣
述轩岐之蕴，广汤液之用，约之以三百九十七法，一百一十三方，而《金匮》不在其数，其立法之妙，为治之活，于主
客阴阳之变，莫不融贯，是在乎用之者之神而明之耳。后之论足经，论卒病，论三纲，论六气，论伤寒即杂证之一，纷
纷聚讼，返而求之仲圣之书，其活泼泼地者，固无乎不包也，故治病须用活法。
我曾说，张仲景（长沙太守）的论述，在严谨之中蕴含着灵活变化的法则。自然界的气候变化并非一成不变，有主气（每年固定不变的气候规律），有客气（每年轮转变化的异常气候）；人体的脏腑属性也不尽相同，有阴脏（阳气不足、易生内寒的体质），有阳脏（阳气偏盛、易生内热的体质）。春温、夏热、秋燥、冬寒，这是四季固定的气候特征；厥阴风木化为初之气，少阴君火化为二之气，少阳相火化为三之气，太阴湿土化为四之气，阳明燥金化为五之气，太阳寒水化为终之气，这是六步气运的常规度数。因此，寒邪必定在冬季伤人，而温病与热病必然发生在春季和夏季，这是大概的情况。
然而，从五运（木火土金水五行之气的运行）的角度来看，土运和金运的交替迁变没有定常；从六气（风寒暑湿燥火）的角度来看，司天（主管上半年气候）、在泉（主管下半年气候）、左间（司天左侧的气）、右间（司天右侧的气）的加临影响各不相同，再加上胜复（克制与被克制后的报复性反应）的道理，太过（气运过盛）与不及（气运衰弱）的数量差异，于是春夏季节也会有伤寒，隆冬时节也并非没有温病，这就是所谓的“非其时而有其气”（在不该出现某种气候的时候出现了这种气候），不能拘泥于节气时令的常规。《素问》说：地势极高的地方，冬天的寒气常在；地势极低的地方，春天的暖气常在。《灵枢》说：将一天分为四个时段，日出为春，日中为夏，日落为秋，夜半为冬。这些都是从灵活变化的角度来阐述的。
那些解说的人，认为伤寒必定主治于冬季，对于桂枝汤（调和营卫的方剂）、麻黄汤（发汗解表的方剂）以及三阴病（太阴、少阴、厥阴病证）的各种辛热药剂，必定只适用于冬季的伤寒，而不可用于春夏之时，拘泥于时令，对于变化之理，恐怕有所欠缺吧！《通天篇》说，人有太阴之人、少阴之人、太阳之人、少阳之人、阴阳和平之人，以及那五五二十五种人的政情，《本脏篇》又言及二十五种变化。从前夏英公（夏竦）禀赋特异，睡觉时身体冷得像僵死一样，常年服用仙茅、钟乳石、硫黄，不知节制，小吏偷吃这些药，就因发疽疮而死。而太阳之人（阳气旺盛者），则饮食生冷而不知节制，纵欲房事而不感到疲劳，这其中的阴阳反差，何止是天壤之别，所以有“从化”的说法。所谓“从”，是顺应大环境的气候；所谓“化”，是脏腑自身的属性。阴脏的人多寒，阳脏的人多热，所谓阴从阳化、阳从阴化、热从寒化、寒从热化，也都是从灵活变化的角度而言，尤其不可拘泥于温凉寒暖的常规。
由于运气主客的不同，再加上脏腑阴阳的区别，疾病便呈现出千态万状，无法穷尽探究。张仲圣（张仲景）阐述黄帝岐伯的深意，广泛运用汤液疗法，归纳为三百九十七法，一百一十三方，而《金匮要略》不在此数之内，其立法的精妙，治疗方法的灵活，对于主客阴阳的变化，无不融会贯通，这在于使用者能否神妙地领悟并阐明它。后世讨论足经、卒病（急性病）、三纲（风伤卫、寒伤营、风寒两伤营卫）、六气、伤寒即杂证之一等观点，纷纷争论不休，若返回来探求张仲景的书，其中活泼泼的生命力，原本无所不包，所以治病必须使用灵活的方法。
I have said that Zhang Zhongjing’s (the Grand Commandant of Changsha) discussions, while rigorous, contain flexible and adaptable methods. The atmospheric changes of heaven are not uniform; there is the Principal Qi (the fixed climatic pattern of each year) and the Guest Qi (the rotating, abnormal climatic patterns). The nature of human internal organs also varies; there are Yin Zang (constitutions prone to internal cold due to deficient Yang) and Yang Zang (constitutions prone to internal heat due to excess Yang). Spring warmth, summer heat, autumn dryness, and winter cold are the fixed positions of the four seasons; Jueyin Wind transforms into the First Qi, Shaoyin Heat transforms into the Second Qi, Shaoyang Fire transforms into the Third Qi, Taiyin Dampness transforms into the Fourth Qi, Yangming Dryness transforms into the Fifth Qi, and Taiyang Cold transforms into the Final Qi; this is the constant measure of the Six Steps. Therefore, Cold must injure in Winter, while Warmth and Heat must occur in Spring and Summer; this is the general rule.
However, speaking from the perspective of the Five Movements (Wu Yun), the succession of Earth Movement and Metal Movement is irregular; speaking from the perspective of the Six Qi, the influences of Si Tian (Qi governing the first half of the year), Zai Quan (Qi governing the second half of the year), Zuo Jian (Left Intercalary Qi), and You Jian (Right Intercalary Qi) differ individually. Added to this are the principles of Sheng and Fu (excess and deficiency leading to counter-reaction), and the numbers of Tai Guo (excess) and Bu Ji (deficiency). Thus, there can be Shang Han (Cold Damage) in Spring and Summer, and Wen Bing (Warm Diseases) in deep Winter. This is what is meant by "having the Qi of one season at the time of another," and one cannot rigidly adhere to the norms of solar terms and seasons. *Su Wen* states: "In places of extreme height, Winter Qi is always present; in places of extreme depth, Spring Qi is always present." *Ling Shu* states: "Dividing a day into four times, sunrise is Spring, noon is Summer, sunset is Autumn, and midnight is Winter." All these are discussed from the perspective of flexible methods.
Those who interpret the matter insist that Shang Han must be treated in Winter, and that Guizhi Tang (Cinnamon Twig Decoction), Mahuang Tang (Ephedra Decoction), and various acrid-warm agents for the Three Yin diseases must only be used for Winter Shang Han, and cannot be applied in Spring and Summer. Being rigid about seasonal timing, do they not lack completeness regarding the principle of change? *Tongtian Pian* states that there are Ta Yin persons, Shao Yin persons, Tai Yang persons, Shao Yang persons, and Yin-Yang Peaceful persons, along with the governance of twenty-five types of people derived from five groups of five. *Ben Zang Pian* further discusses twenty-five variations. In the past, Xia Yinggong (Xia Song) had an exceptional constitution; when sleeping, his body was as cold as if stiffened. He constantly consumed Xian Mao (Curculiginis Rhizoma), Zhong Ru (Gypsum Fibrosum), and Liu Huang (Sulfur) without limit. A minor clerk secretly ate some and died from developing a carbuncle. Conversely, Tai Yang persons (those with abundant Yang) consume raw and cold foods without restraint and indulge in sexual activity without fatigue. The reversal of Yin and Yang between them is like heaven and earth. Therefore, there is the theory of Cong Hua (following transformation). "Cong" refers to following the macro-climate; "Hua" refers to the nature of the Zang organs. Those with Yin Zang tend toward cold; those with Yang Zang tend toward heat. This is called "Yin follows Yang transformation, Yang follows Yin transformation, heat follows cold transformation, and cold follows heat transformation." These are all discussed as flexible methods, and one should especially not be bound by the norms of warm, cool, cold, and hot treatments.
Due to the differences in Principal and Guest Qi, combined with the distinctions of Zang-Fu Yin and Yang, diseases manifest in thousands of forms, impossible to fully exhaust or interrogate. Master Zhong (Zhang Zhongjing) expounded the profound meaning of Xuanyuan (Yellow Emperor) and Qibo, broadening the use of Tang Ye (decoctions), summarizing them into 397 methods and 113 formulas (excluding *Jingui Yaolue*). The subtlety of his established methods and the flexibility of treatment integrate seamlessly with the changes of Principal, Guest, Yin, and Yang. This depends on whether the practitioner can divine and clarify it. Later scholars debated the Foot meridians, Cu Bing (acute diseases), the Three Guidelines (Wind injuring Wei, Cold injuring Ying, Wind-Cold injuring both Ying and Wei), Six Qi, and the idea that Shang Han is merely one type of miscellaneous disease, engaging in endless disputes. Returning to seek answers in Master Zhong’s books, the vibrant vitality within them inherently encompasses everything. Therefore, treating diseases requires flexible methods.