内经云。太阳者三阳也。其气最尊。唯心君得主之。故心为阳中之太阳。要为元气之极浓。是以为经为父。而为十
二经之纲维。人生于阳。阳气一丝未断不死。是以有取于纯阳。而要其所以为阳。即神明之气故也。其气高而在上。故
六阳之气。皆从而上于头。自额颅巅顶。及后之风府。皆太阳也。其气本于少阴肾。又自太冲而上。总于督脉。而极于
背之五行。故自顶脊及腰背膂。皆太阳也。其气浮而充满与卫气俱。经云。阳因而上。卫外者也。唯其卫外。故主一身
之充肤泽毛。凡为外之卫者。皆太阳也。主内而专精。故精则养神。主外而固密。故宜静。而躁则消亡。若此气稍有不
精不密。则内外之病皆举矣。内之为病也。发寒热壅肿痿厥 痛。及为结隔。亢则如霹雳风雨。外之为病也。风寒袭之。
为伤寒中风。其在经络部位受病。则头痛项强。肩背腰膂骨节疼痛。通身发寒热。伤寒畏寒。伤风畏风。寒则伤营。风
则伤卫。其所以纳膀胱。而病不归膀胱者。以膀胱为州都之官。主表非其所事。唯日久而行其经尽。则有犯及膀胱。为
渴而小便不利。是从其经之本也。乃伤寒诸家竞以脉浮为太阳膀胱病而绝不计太阳为何物。动指膀胱当之。而抑知膀胱
固非病之所主也。
四时六气。五运司天。是为三合。缘其三合。故为气交。气交则变而人应之。是以外感百病生焉。人在气交之中故
也。四时六气之正。内经全不列证。其不列证者。以正六气。本五行四时之顺。阴阳升降之宜。果合气宜。何尝有病。
其所以有病者。以其气之至。常有太过不及之差。或有加临乘除。主客胜负。以参合其间。则亦恒能变本气之用。而为
太过不及之异。是运气司天。苟相值相加。斯不能无病也。若谓不关于人。则该年之生息凡物类之盛育衰耗。草木之发
荣黄落。每年不同。此非其气交而变者乎。人在气交之中。岂无相感之故。盖外有所感。而内之所应。苟失其和。病于
是乎作也。夫外之所感。本与内伤七情不同。内伤从素性偏僻。煎迫之有素。脏腑禀受。浓薄之不一而得。然由此而外
感。原各有内气之应。非可止以外邪治之也。内经别有奇恒一门。以收内伤。其法虽与运气之外感霄壤。而观运气七篇。
其病丛列。帝以条绪纷纭。复询岐伯。以致一之道。而岐伯答病机十九条以约之。其致病皆由岁气交加。外淫而甚。其
中火热独多者。以二火司天故也。岐伯恐帝未得圆通。首戒以无失气宜。而继之以无者求之。虚者责之。盖谓有内证夹
之。当更加之意。初不以外感之有余。印定后人眼目也。刘守真高明之士。亦复不察。而执以为脏腑内外百病。皆尽于
此。衍为原病式一书。尽以有余属之火甚之症。十恒八九。特信寒凉攻泻之法。立方以误后人。极于张子和儒门事亲一
书。专以汗吐下三法。从事峻剂法。以为邪祛正立。否则关门闭盗。后学不察。仍其偏说。由于不读内经。而未 奇恒
之一门耳。夫人脏腑阴阳之气。有有余不足。邪之所凑。其气必虚。盗乘其虚入劫衄其主。当是之时。攻盗乎。救主乎。
若救主而用攻。杀其主而已矣。故要而论之。运气加临为病者。不越运气之有余不足。以补泻之。而必须内固其脏腑。
脏腑之有余不足。而内为病者。纵有运气之感。仍当治以脏腑之内伤。而略祛其微邪。以靖内气。所谓养正则邪自去者
此也。然则治外感之纯用攻者。要非为善法也。
《内经》说：太阳是三阳之一。它的阳气最为尊贵，只有心君（心脏）能够主宰它。所以心被称为“阳中之太阳”，这主要是因为它是元气最浓厚的地方。因此，太阳经作为诸经之父，是十二经脉的纲领和维系者。人禀受于阳而生，只要阳气有一丝未断就不会死亡，所以要追求纯阳的状态，并探究其之所以为阳的本质，即在于它是神明之气。
这种气位置高而在上，所以六条阳经的气都向上汇聚到头面部。从额头、颅顶到后颈的风府穴，都属于太阳经的范围。太阳之气根源于少阴肾，又沿着太冲脉向上，总汇于督脉，并极盛于背部的五行区域。所以从头顶、脊柱到腰背肌肉，都属于太阳经的范围。
太阳之气浮越且充满，与卫气相伴而行。《内经》说：“阳气向上行，负责保卫体表。”正因为具有保卫体表的功能，所以它主管一身肌肤的充润和毛发的泽亮。凡是负责外部防御的，都属于太阳经。
太阳经主内守而专精，所以精气充足则能滋养神志；主外固密，所以适宜保持安静，如果躁动则会耗散消亡。如果这种气稍微不够精纯或固密，那么内外的疾病都会发生。
在内方面的病变，表现为寒热、壅滞肿胀、痿证、厥逆、疼痛，以及结胸隔塞等症。病情亢盛时，如同霹雳风雨般猛烈。在外方面的病变，风寒侵袭人体，导致伤寒或中风。如果在经络部位受病，就会出现头痛、项强、肩背腰脊及骨节疼痛，全身发冷发热。患伤寒者畏寒，患伤风者畏风。寒邪容易损伤营气，风邪容易损伤卫气。
虽然病邪最终会传入膀胱，但病症并不主要归属于膀胱，因为膀胱是“州都之官”（储藏尿液的器官），其主要职责在表而非主治这些病症。只有当病程日久，邪气沿经脉传变到底，才会波及膀胱，出现口渴和小便不利的症状，这是顺着经脉本源传变的结果。然而，历代研究伤寒的医家竞相将脉浮视为太阳膀胱病的证据，却完全不计较太阳究竟是什么，动不动就指认膀胱来对应此病。他们哪里知道，膀胱固然不是疾病的主宰所在。
四季的六气变化，五运的司天规律，这三者结合称为“三合”。正因为有这三者的结合，所以形成了“气交”。气交之处产生变化，人体随之感应，因此外感百病由此而生。人生活在气交之中，正是如此。
《内经》并没有专门列出四时六气的正常气候所导致的病症。之所以不列证，是因为正常的六气本应顺应五行和四季的变化，符合阴阳升降的规律。如果真正契合了气候的适宜状态，怎么会生病呢？之所以会生病，是因为气候的到来，常有太过或不及的差异，或者有加临、乘除等复杂情况，主气与客气的胜负参杂其中，从而改变本气的作用，产生太过或不及的异常。因此，运气司天的规律，如果相互值遇叠加，就不能不产生疾病。
如果说这与人类无关，那么该年份生物的生存繁衍、万物的盛衰枯荣、草木的生长凋零，每年都不相同。这难道不是气交变化的结果吗？人生活在气交之中，岂没有相互感应的道理？大概是因为外有所感，而内的反应如果失去了和谐，疾病就在这里产生了。
外感致病，本来与内伤七情不同。内伤是由于平素性情偏颇，长期煎熬逼迫，脏腑禀赋浓薄不一而得病。然而，由此引发的外感，原本也各有内在气息的感应，不能仅仅用治疗外邪的方法来处理。
《内经》另有“奇恒”一门，用来收录内伤病。这种方法虽然与运气所致的外感截然不同，但在观察运气七篇中，病症罗列繁杂，黄帝因条理纷纭，再次询问岐伯，以求得一以贯之的道理。岐伯用“病机十九条”来概括它们。这些致病因素都源于岁气交加，外邪淫盛，其中火热之邪独多，是因为二火（少阴君火、少阳相火）司天的缘故。
岐伯担心黄帝未能圆通理解，首先告诫不要违背气候的适宜规律，接着又说“无者求之，虚者责之”。意思是说，如果有内证夹杂其中，应当更加留意。起初并不是以外感有余（实证）来固定后人的眼光。刘完素（字守真）是一位高明之士，也没有仔细考察这一点，反而固执地认为脏腑内外百病都包含在这十九条中，进而撰写了《原病式》一书，将所有有余的症状都归结为火甚之症，十有八九。他特别信奉寒凉攻泻的方法，创立方剂误导后人。到了张子和的《儒门事亲》一书，专门使用汗、吐、下三种方法，从事峻猛药剂的治疗，认为邪气祛除正气就能确立，否则就像关门闭盗一样危险。后世学者不加考察，仍沿袭这种片面说法，原因在于没有阅读《内经》，忽略了“奇恒”这一门类。
人的脏腑阴阳之气，有有余和不足之分。邪气聚集的地方，那里的正气必然虚弱。盗贼趁着虚弱进入劫掠主人的财物。在这个时候，是攻击盗贼呢，还是救助主人呢？如果救助主人却使用攻伐之法，那就等于杀死了主人。
所以总的来说，由运气加临引起的疾病，不外乎运用补泻法来调节运气的有余和不足，并且必须内部巩固脏腑。对于脏腑有余不足引起的内伤疾病，即使有感于运气变化，仍然应当以内伤脏腑的方法来治疗，略微驱散微弱的邪气，以安定内在之气。这就是所谓“养正则邪自去”的道理。然而，治疗外感病纯粹使用攻伐之法，终究不是好的方法。
The *Neijing* (Inner Canon) states: Taiyang (Greater Yang) is one of the Three Yang meridians. Its qi (vital energy) is the most dignified, and only the Heart Monarch (Heart) has dominion over it. Therefore, the Heart is called the "Taiyang within Yang," primarily because it is where Yuanqi (Original Qi) is most concentrated. Thus, the Taiyang meridian serves as the father of the meridians and acts as the纲维 (guiding framework) for the Twelve Meridians. Humans are born from Yang; as long as a thread of Yang qi remains unbroken, death does not occur. Hence, there is a pursuit of Pure Yang, seeking its essence, which is the Qi of Spirit (Shen).
This qi resides high and above; therefore, the qi of all Six Yang meridians ascends to the head. From the forehead and vertex to the Fengfu (GV16) point at the back of the neck, these areas belong to Taiyang. The qi of Taiyang originates from Shaoyin Kidney, ascends via the Taichong channel, converges with the Du Mai (Governing Vessel), and reaches its peak in the Five Elements region of the back. Thus, from the crown, spine, to the loins and back muscles, these belong to Taiyang.
The qi of Taiyang is floating and abundant, accompanying Wei Qi (Defensive Qi). The *Neijing* says: "Yang qi moves upward and guards the exterior." Because it guards the exterior, it governs the fullness of the skin and flesh and the luster of the hair. Anything responsible for external defense belongs to Taiyang.
Taiyang governs internal retention with specialization; thus, when Jing (Essence) is sufficient, it nourishes Shen (Spirit). It governs external solidity, so it prefers stillness; agitation leads to consumption and loss. If this qi becomes slightly impure or insecure, diseases both internal and external will arise.
Internally, disease manifests as chills and fever, stagnation and swelling, flaccidity, reversal cold/heat (Jue-Ni), pain, as well as chest binding and diaphragmatic obstruction. When severe, it resembles thunderbolts and storms. Externally, Wind-Cold invades, causing Shanghan (Cold Damage) or Shangfeng (Wind Injury). If disease occurs in the meridian regions, symptoms include headache, stiff neck, pain in the shoulders, back, loins, spine, and joints, along with generalized chills and fever. Those with Cold Damage fear cold; those with Wind Injury fear wind. Cold injures Ying Qi (Nutritive Qi); Wind injures Wei Qi (Defensive Qi).
Although pathogens eventually enter the Bladder, the pathology is not primarily attributed to the Bladder, because the Bladder is the "Official of the Metropolis" (responsible for storing urine), and its function lies in the exterior, not in governing these specific pathologies. Only after prolonged duration, when pathogens traverse the meridian to its end, do they affect the Bladder, causing thirst and difficult urination. This follows the root of the meridian transmission. However, various scholars of Shanghan compete to regard floating pulse as evidence of Taiyang-Bladder disease, completely disregarding what Taiyang actually is, and arbitrarily attributing it to the Bladder. They fail to realize that the Bladder is indeed not the master of the disease.
The six Qi of the four seasons and the Wu Yun (Five Movements) Si Tian (Heavenly Ruler) constitute the "Three Harmonies." Due to this convergence, it forms the "Qi Intersection" (Qi Jiao). Changes at the Qi Intersection cause human response, giving rise to exogenous hundred diseases. Humans live within the Qi Intersection.
The *Neijing* does not list syndromes for the normal state of the Six Qi of the four seasons. It omits them because normal Six Qi should follow the order of Five Elements and four seasons, adhering to the proper ascent and descent of Yin and Yang. If one truly aligns with the appropriate climate, how could illness occur? Illness arises because the arrival of Qi often has discrepancies of excess (Tai Guo) or deficiency (Bu Ji), or involves complex interactions like addition, subtraction, dominance, and subordination between Host and Guest Qi. These alter the function of the original Qi, creating abnormalities of excess or deficiency. Therefore, if Si Tian patterns overlap, disease is inevitable.
If one claims this has nothing to do with humans, consider that the survival and reproduction of living things, the flourishing and decline of all species, and the growth and withering of plants vary annually. Is this not due to changes in the Qi Intersection? Since humans exist within the Qi Intersection, must there not be mutual resonance? Generally, external stimulation combined with an internal response that loses harmony results in disease.
Exogenous disease differs fundamentally from endogenous injury caused by the Seven Emotions. Endogenous injury stems from inherent personality biases, long-term mental strain, and varying constitutional thickness/thinness of Zang-Fu organs. However, subsequent exogenous infections always have corresponding internal Qi responses; they cannot be treated solely by expelling external pathogens.
The *Neijing* has a separate category called "Qi Heng" (Strange and Constant) to collect endogenous diseases. Although this method is vastly different from exogenous diseases caused by Yun Qi (Luck/Movement), in observing the Seven Chapters on Yun Qi, the listed diseases are numerous. The Yellow Emperor, finding the details chaotic, asked Qibo again to find a unifying principle. Qibo summarized them using the "Nineteen Pathogenesis Formulas." These pathogenic factors all stem from the intersection of annual Qi, with severe external invasion. Among them, Fire and Heat are predominant due to the influence of the Two Fires (Shao Yin Ministerial Fire and Shao Yang Triple Burner Fire).
Qibo, fearing the Emperor might not grasp the comprehensive nature, first warned against losing sight of the appropriateness of Qi, then added, "Seek the non-existent [pathology], blame the deficient." This implies that if internal signs are involved, extra attention is needed. Initially, it was not about fixing later generations' perspectives based on exogenous excess. Liu Wansu (courtesy name Shouzhen), though a brilliant scholar, failed to examine this carefully. He stubbornly believed that all internal and external diseases of the Zang-Fu were contained within these nineteen formulas, subsequently writing the *Yuan Bing Shi* (Treatise on Original Disease Patterns). He attributed almost eighty percent of excess conditions to excessive Fire. He particularly advocated cold and purgative methods, prescribing formulas that misled later generations. This culminated in Zhang Zhongjing's disciple Zhang Zihe's *Rumen Shiqin* (Affairs of the Confucian Gate), which specialized in the three methods of sweating, vomiting, and purging using harsh agents, believing that once pathogens are expelled, healthy Qi stands; otherwise, it is like locking the door while thieves are inside. Later students, without careful examination, continued this biased view because they did not read the *Neijing* and ignored the "Qi Heng" category.
The Qi of Yin and Yang in human Zang-Fu organs has both excess and deficiency. Where pathogens gather, Qi must be deficient. Thieves take advantage of weakness to rob the host. At such times, should one attack the thief or save the host? If saving the host by using attack methods, one merely kills the host.
Therefore, generally speaking, diseases caused by Yun Qi superposition are addressed by tonifying or reducing the excess or deficiency of Yun Qi, while necessarily consolidating the internal Zang-Fu. For internal diseases caused by Zang-Fu excess or deficiency, even if influenced by Yun Qi, treatment should focus on internal Zang-Fu injury, slightly dispelling minor pathogens to calm internal Qi. This is what is meant by "nourishing the upright causes the evil to depart." Consequently, treating exogenous diseases purely with attacking methods is ultimately not a good approach.