天地至大，人物至广，不外阴阳五行之理。五运，即五行也。六气，即三阴三阳也。故木、火、土、金、
水曰五运；厥阴、少阴、太阴、少阳、阳明、太阳曰六气。五运合五行，而六气亦合五行。天以此成四时而生
万物，
人以此成有形而合无形。是五运六气实医学之根源，神农本之而着药性，黄帝本之而着《内经》，仲师本之
而撰《伤寒》、《金匮》。今人但知风、热、湿、火、燥、寒为病，岂知厥阴主风，风，木也；少阴、少阳主
热，热，火也；太阴主湿，湿，土也；阳明主燥，燥，金也；太阳主寒，寒，水也。此风、热、湿、火、燥、
寒之病，而五运六气即主之，五脏六腑亦因之。其本末不可不察也！
六淫外感之说，世多不得其解，谓人外感天之六淫则为病，而孰知其非也。盖厥阴、少阴、太阴、少阳、
阳明、太阳曰六气，风、热、湿、火、燥、寒曰六淫。天有之，人亦有之。故居其内以通脏腑者，六气也；居
其外以通于天者，六淫也。天之六淫，与人之六淫，无时不感，讵必病也？《天元纪大论》云∶厥阴之上，
风气主之∶少阴之上，热气主之；太阴之上，湿气主之；少阳之上，相火主之；阳明之上，燥气主之；太阳
之上，寒气主之。所谓本也，是谓六元。由此例之，则三阴三阳之六气，在下为标，下即内也；而风、热、湿、
火、燥、寒之六淫，在上为本，上即外也。六淫在上而在外，故曰外感，感犹通也。故外感之说，其义有二∶
一言六淫外通于天；一
言六淫主外通于六气。义虽有二，总谓六淫在人而不在天，凡有所病，皆本人身之六淫，而非天之六淫也。且
独不观卒病论乎！发热，汗出，恶风，脉缓者，名为中风。是中风之名，从人身而定也。或已发热，或未发
热，必恶寒、体痛、呕逆，脉阴阳俱紧者，名为伤寒。是伤寒之名，从人身而定也，非外至也，若果外至，
胡不曰六淫外中，六淫外伤，而必曰外感也？世多不知此义，一遇病，辄云外感，岂无病时遂不感耶？甚矣！
其聩聩也。
天地极为宏大，万物极为繁多，都不超出阴阳五行的道理。五运，就是五行。六气，就是三阴三阳。所以木、火、土、金、水称为五运；厥阴、少阴、太阴、少阳、阳明、太阳称为六气。五运与五行相合，而六气也与五行相合。天凭借这些形成四季并化生万物，人凭借这些形成有形的躯体并与无形的规律相契合。因此，五运六气确实是医学的根源，神农氏依据它来撰写《本草》（药物学著作），黄帝依据它来撰写《黄帝内经》，张仲景依据它来撰写《伤寒杂病论》和《金匮要略》。现在的人只知道风、热、湿、火、燥、寒是致病因素，哪里知道厥阴主风，风属于木；少阴、少阳主热，热属于火；太阴主湿，湿属于土；阳明主燥，燥属于金；太阳主寒，寒属于水呢？这些由风、热、湿、火、燥、寒引起的疾病，实际上都由五运六气所主宰，五脏六腑也因此受到影响。其中的根本与末节不可不仔细考察啊！
关于“六淫外感”的说法，世人大多不能理解其真意，认为人受到自然界六淫邪气的侵袭就会生病，这其实是错误的。大概厥阴、少阴、太阴、少阳、阳明、太阳称为六气，风、热、湿、火、燥、寒称为六淫。自然界有这些，人体内部也有这些。所以，居于体内以通达脏腑的是六气；居于体外以通达于天的则是六淫。自然界的六淫与人体内的六淫，无时无刻不在相互感应，难道一定会导致生病吗？《素问·天元纪大论》说：厥阴之上，风气主之；少阴之上，热气主之；太阴之上，湿气主之；少阳之上，相火主之；阳明之上，燥气主之；太阳之上，寒气主之。这就是所谓的“本”，也就是“六元”。由此类推，那么三阴三阳的六气，在下位为“标”，下即指体内；而风、热、湿、火、燥、寒的六淫，在上位为“本”，上即指体外。六淫位于上位且在体外，所以称为“外感”，“感”的意思就是相通。所以“外感”这一说法，其含义有两层：一层是说六淫在体外通达于天；另一层是说六淫主管体外通达于体内的六气。含义虽然有两层，但总归是说六淫在于人体内而不在于外界，凡是有所生病，都是源于人身内部的六淫失调，而不是因为外界的六淫邪气。况且，难道没有看过《伤寒杂病论》吗？出现发热、汗出、恶风、脉象缓弱的症状，命名为中风。这个“中风”的名称，是根据人体自身的反应来确定的。或者已经发热，或者尚未发热，必定伴有恶寒、身体疼痛、呕吐逆气，寸关尺三部脉象都紧，命名为伤寒。这个“伤寒”的名称，也是根据人体自身来确定的，并非指外来的邪气，如果真的指外来邪气，为什么不叫“六淫外中”、“六淫外伤”，而一定要叫“外感”呢？世人大都不知道这个道理，一遇到生病，就说是外感，难道没生病的时候就不存在感应了吗？这也太糊涂了！
Heaven and Earth are extremely vast, and all living things are numerous; none of them transcend the principles of Yin-Yang and the Five Elements. The Five Movements (Wuyun) refer to the Five Elements. The Six Qi (Liuqi) refer to the Three Yin and Three Yang. Therefore, Wood, Fire, Earth, Metal, and Water are called the Five Movements; Jueyin, Shaoyin, Taiyin, Shaoyang, Yangming, and Taiyang are called the Six Qi. The Five Movements correspond with the Five Elements, and the Six Qi also correspond with the Five Elements. Heaven utilizes these to form the four seasons and generate all things, while humans utilize these to form tangible bodies and align with intangible laws. Thus, the Five Movements and Six Qi are indeed the root of medicine. Shennong based his work on this principle to write the *Bencao* (Materia Medica); the Yellow Emperor based his work on this principle to write the *Huangdi Neijing* (Yellow Emperor's Inner Canon); and Zhang Zhongjing based his work on this principle to compose the *Shanghan Zabing Lun* (Treatise on Cold Pathogenic Diseases) and the *Jingui Yaolue* (Essential Prescriptions of the Golden Cabinet).
People today only know that Wind, Heat, Dampness, Fire, Dryness, and Cold are pathogenic factors, but how do they know that Jueyin governs Wind, and Wind belongs to Wood; Shaoyin and Shaoyang govern Heat, and Heat belongs to Fire; Taiyin governs Dampness, and Dampness belongs to Earth; Yangming governs Dryness, and Dryness belongs to Metal; Taiyang governs Cold, and Cold belongs to Water? These diseases caused by Wind, Heat, Dampness, Fire, Dryness, and Cold are actually governed by the Five Movements and Six Qi, and the Zang-Fu organs are consequently affected. The root and branches thereof must be carefully examined!
Regarding the theory of "Six Excesses (Liuyin) External Contraction," most people in the world fail to understand its true meaning. They believe that when a person is externally contracted by the Six Excesses of heaven, disease occurs; however, this is incorrect. Essentially, Jueyin, Shaoyin, Taiyin, Shaoyang, Yangming, and Taiyang are referred to as the Six Qi, while Wind, Heat, Dampness, Fire, Dryness, and Cold are referred to as the Six Excesses. These exist both in nature and within the human body. Therefore, what resides internally to connect with the Zang-Fu organs is the Six Qi; what resides externally to connect with Heaven is the Six Excesses. The Six Excesses of Heaven and the Six Excesses within humans are in constant interaction at all times; does this necessarily lead to disease? The *Suwen: Tianyuanji Dalun* states: "Above Jueyin, Wind Qi governs; above Shaoyin, Heat Qi governs; above Taiyin, Dampness Qi governs; above Shaoyang, Ministerial Fire governs; above Yangming, Dryness Qi governs; above Taiyang, Cold Qi governs." This is referred to as the "Root" (Ben), also known as the "Six Origins" (Liuyuan). By analogy, the Six Qi of the Three Yin and Three Yang are the "Branch" (Biao) located below, where "below" refers to the interior; whereas the Six Excesses of Wind, Heat, Dampness, Fire, Dryness, and Cold are the "Root" (Ben) located above, where "above" refers to the exterior. Since the Six Excesses are located above and outside, they are termed "External Contraction" (Waigan). "Contraction" here implies connection or resonance. Thus, the concept of "External Contraction" has two meanings: one is that the Six Excesses externally connect with Heaven; the other is that the Six Excesses govern the external connection with the internal Six Qi. Although there are two meanings, it ultimately asserts that the Six Excesses reside within the human body rather than in the external environment. Any disease that arises stems from the dysregulation of the Six Excesses within the person, not from external pathogenic factors.
Furthermore, have you not read the *Shanghan Lun*? When symptoms include fever, sweating, aversion to wind, and a slow pulse, it is named "Zhongfeng" (Wind Strike). This name for "Wind Strike" is determined based on the body's own response. If there is fever or no fever, accompanied by aversion to cold, body pain, vomiting, and a tight pulse in both Yin and Yang positions, it is named "Shanghan" (Cold Damage). This name for "Cold Damage" is also determined based on the body itself, not indicating an external invasion. If it truly indicated an external invasion, why would it not be called "Six Excesses External Strike" or "Six Excesses External Injury," but instead must be called "External Contraction"? Most people in the world do not understand this principle. Upon encountering illness, they immediately claim it is due to external contraction. Does this imply that without illness, there is no interaction? How ignorant this is!