The 6 classifications of disease of the Shanghan Lun are composed of 3 Yin 3 Yang¹, each mentioned by name in correlation to certain disease characteristics and specific therapeutic methods. For example in line 1 there is the outline of a Tai Yang pathology:

“In disease of Tai Yang, the pulse is floating, the head and nape are stiff and painful, and there is aversion to cold.”²

The Shanghan Lun does not offer anywhere in the text an explanation or definition of them as a group, leaving the subject of the 6 classifications open to interpretation.

The concept of the division of Yin and Yang into 6 classifications, as well as the names given to each one of them appears in the Neijing:

“The qi of both yin and yang may be present in large or small quantities, hence one speaks of the three yin and three yang.”³

Yin and Yang are fundamental cosmic forces rooted in Chinese thought from early antiquity. The body is discussed in the Neijing as a direct continuum of these cosmic forces. Maintaining health was perceived as adjusting the lifestyle and functions of the body to the natural cycles of the universe. Each of the 6 divisions is linked in the Neijing to specific organs and their correlating circulatory tracts, illustrating the influence of the external cosmic forces on the internal body processes and functions. In Suwen chapter 31 there is a description of the day by day progression of a shanghan disease. In this chapter the 6 divisions appear to be successive stages of febrile disease illustrating the damage that results as the disease penetrates the different stages and progresses from a superficial disease to a life-threatening illness.

The Shanghan Lun, written about a century later, was a different text altogether. While it does seem to draw upon notions and terminology from the Neijing, it does not dwell on theoretical or cosmological aspects, it is a practical guide predominantly focused on clinical aspects of diagnosis and treatment in the different manifestations of disease. Disease was not discussed in terms of adherence to resonating forces surrounding the body. Disease was discussed in terms of symptoms, seeking only to provide practical therapeutic solutions. There is no indication within the lines of the text that the 6 divisions of the Shanghan Lun are linked to specific circulatory tracts or organs. Otsuka Keisetsu concluded following extensive research into the Shanghan Lun:

“Zhang was a physician in the tradition of the Inner Canon who acknowledges (in his preface) the importance he accorded to the world view – absent from the text of the Treatise.”⁴

 While the theoretical basis is not presented in the Shanghan Lun, it is clear that the text is not an arbitrary list of symptoms and treatments, but rather a concisely systematic doctrine. However, it is extremely complicated to grasp the guiding principles underlying this doctrine. For example, when one reads line 318 it seems like a list of unrelated symptoms which could all respond to the same herbal remedy without need for differential diagnosis.

“When in lesser yin disease (there is) counterflow cold of the limbs, the person may cough or have palpitations, or inhibited urination, or pain in the abdomen, or diarrhea with rectal heaviness, si ni san governs.”⁵

To the scholar educated in the different clauses of the Shanghan Lun, it is clear that there is a sophisticated and complex system of diagnosis which is revealed through a cross-sectional examination of the different mentions of the same symptom in different categories with different context and relating to different remedies. As a result the palpitations mentioned in line 318 are nothing like the palpitations mentioned in line 102:

“When in cold damage (that has lasted for) two or three days, (there are) palpitations and vexation in the heart, xiao jian zhong tang governs.”⁶

In order to form a systemic analysis of the Shanghan Lun it is necessary to deduce from the clinical descriptions and the formulas given in the text, and combine different lines scattered throughout the text. This is not a simple task, and if the Shanghan Lun were to become a popular clinical guide for the growing status of scholar physicians, it needed to be more approachable. The association of the Shanghan Lun with the theoretical foundations of the Neijing, began as soon as the 3^rd century with Wang Shuhe who collected and edited remaining fragments of the original text.⁷ In the 12^th century the Shanghan Lun became a text central to the development of medicine in China under the supervision of an official government policy which advocated for regulation of medicine as a means to secure the stability of rule. This was compatible with how the Shanghan Lun was received by the scholars and physicians of the Song dynasty who received the historical task of implementing the text in practice. They strove for consolidation of the ancient medical doctrines into a unified medical system as a basis for education and regulation of the establishing the new status of the scholar physician.

Consequently, despite the apparent conceptual differences, interpretations and commentaries all relied heavily upon the concepts stemming for the Neijing.

Song dynasty physician Zhu Gong was the first to establish the direct connection between the twelve circulation tracts and corresponding viscera of the Neijing and the disease classifications of the Shanghan Lun.⁸ In his book published in 1108 he stated:

“To treat cold damage one must first know the conduits and networks. If one does not know the conduits and networks, one roams around in muddled confusion without knowing the location of the pathogenic qi”⁹

The first full commentary on the Shanghan Lun, and the most famous one to date, was published in 1144 by Song physician Cheng Wuji.  Titled Annotated Treatise on Cold, this extensive commentary contains an explanation of the Shanghan Lun line after line, based on the theoretical principles stemming from the Neijing.¹⁰

Asaf Goldshmidt has remarked on this:

“By doing so, Cheng provided Song medicine, for the first time, a unified nomenclature that enabled physicians to comprehensively understand medical doctrines originating from different medical approaches. In other words, this was one of the first instances in which Song medicine had a unified theoretical basis for physiology and pathology. “¹¹

These interpretations continue to be widely accepted, and extremely influential in the understanding and practical application of the Shanghan Lun. The 6 divisions have consequently been known by the term 6 Jing, translated as 6 warps or 6 channels, referring to the correlation with the circulatory tracts of the body.

Initiating in the late 16^th century, there was an epistemological bifurcation in the perception of the theoretical basis of the Shanghan Lun. This is marked by the publication of a book by Fang Youzhi in 1593 which challenged for the first time the theoretical connection between the Neijing and the Shanghan Lun.¹²

Fang Youzhi a Jiangnan scholar, embarked on a 20 year textual examination, resulting in his book titled A Critical Essay on the Clauses of the Treatise of Cold Damage¹³. He suggested that the version passed down by Wang Shuhe and the later official Song version were incorrect and consequently misleading as clinical guides. He also suggested that the traditional interpretation of the treatise on the basis of the Neijing is incorrect. He directly advocated against the correlation of the 6 divisions with the circulation tracts:

“The [term] Jing of the 6 Jing [of the Shanghan Lun] and the [term] Jing of the channels and network vessels [of the Neijing] is not the same.”¹⁴

While he continued to use the term ‘jing’ for the 6 divisions, he gave it a different definition. For Fang the divisions were regions of the body encompassing all bodily processes and all disease mechanisms.

Fang’s radical re-organization of the text as well as his proposed bodily arrangement of the 6 regions, was not popularly accepted among later scholars. However it did have substantial influence on the perception of the Shanghan Lun and consequently on its practical application. By breaking from the traditional perception of the Shanghan Lun as a continuum of the Neijing he opened the door to novel interpretations based on evidential research of the ancient text combined with current clinical experience. He established the pivotal notion that the divisions act as guiding principles reflecting different response mechanisms of the body to harmful influences. He correlated the Tai Yang, which is the first and significantly largest section in the Shanghan Lun, to the exterior region of the body which comes into direct contact with harmful influences from the outside, therefore presenting in the most concrete way the body’s defense and sustaining mechanisms.  This outlines a model of transmission and transformation of disease for understanding the other 5 divisions, encompassing all the regions and processes of the body.¹⁵

This perception of the Shanghan Lun was adopted by prominent physicians of the Qing dynasty, who continued to develop and expand upon it.¹⁶

An example of this is the 1706 publication of the highly influential book written by the Qing physician Ke Qin¹⁷ titled Anthology for the Revival of Cold Damage (Shanghan laisu ji) 傷寒來蘇集. His interpretation of the Shanghan Lun was built upon the concepts established by Fang:

“Although it took the six divisions as its overarching scheme of organization, each division referring to a specific ‘bounded domain’, it did not thereby restrict itself to the conduits and collaterals, neither was it delimited solely by wind and cold. That is, although [Zhang] Zhongjing employed the terminology of the Inner Canon, he extended the meaning of the six divisions concept.”¹⁸

“[Zhang] Zhongjing’s formulas were composed because of the symptoms [they treat], not because of the conduits [they enter]. Whenever one sees a specific manifestation pattern, one employs the [corresponding] formula. This is [Zhang] Zhongjing’s simple yet flexible method (huofa 活法).”¹⁹

The 17^th century brought a new and unfamiliar challenge to the development of medicine in China. Western scientific concepts were entering China following the arrival of the Jesuits in 1600. The most influential Jesuit of the late Ming, Matteo Ricci initiated the translations of books on natural phenomena from Latin to classical Chinese, inspiring the scholarly elite to re-evaluate their perception of natural studies in these new terms.²⁰ I believe that Fang’s innovative notion that the divisions were guiding principles reflecting different response mechanisms of the body enabled analysis of clinical observations with newly discovered terms and concepts of disease mechanisms. This is expressed in a popular saying which my teachers have often repeated during my studies of the Shanghan Lun:

抓病机，活用经方 – “grasp the mechanism of disease, to flexibly apply the formulas”

Mirroring on Ke Qin’s words: “This is [Zhang] Zhongjing’s simple yet flexible method (huofa 活法)”, this has provided the necessary logic for modern time physicians to research and apply the teachings of the Shanghan Lun to a wide variety diseases combining modern Western understanding of disease with the model of the 6 Jing.

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References

1. The 6 classifications are composed of 3 Yang named: Tai Yang, Yang Ming and Shao Yang; and 3 Yin named: Tai Yin, Shao Yin, Jue Yin.
2. Translation from Mitchell, Craig. Feng, Ye. Weisman, Nigel.  Shang Han Lun on Cold Damage. Brookline, MA: Paradigm Publications. 1999. P. 41.
3. Suwen chapter 66. Translation from: Tessenow, Hermann, and Unschuld, Paul U. 2011. P. 180.
4. Otsuka, Keisetsu 大塚節日. Rinsho oyo Shokanron kaisetsu 臨床應用傷 寒論解說 (Clinically Applicable Explanations of the Cold Damage Treatise). Osaka: Gensha. 1966. Quoted from: Sivin, Natan. Traditional Medicine in Contemporary China. Science, Medicine and Technology in East Asia 2. Ann Arbor: Center for Chinese Studies, The University of Michigan. 1987. P. 87-88.
5. Translation in Mitchell et al. 1999, P. 511.
6. Translation from Ibid. p. 178.
7.  Sivin, Nathan. 1987. P. 49.
8. For more on Zhu Gong’s consolidation of the Shanghan Lun with the meridian theory of the Neijing see: Goldschmidt, Asaf. The Evolution of Chinese Medicine: Song Dynasty, 960–1200. London; New York: Routledge, 2009. P. 158-163.
9. Reference and translation from Scheid, Volker. “Transmitting Chinese Medicine: Changing Perceptions of Body, Pathology and Treatment in Late Imperial China.” Asian Medicine: Tradition and Modernity 8 (January 1, 2013): 299–360. P. 317.
10. Goldschmidt, Asaf. 2009. P. 168-171
11. Ibid p. 169
12. Hanson, Marta. Speaking of Epidemics in Chinese Medicine: Disease and the Geographic Imagination in Late Imperial China. London; New York: Routledge, 2011. P. 12. Sivin, Natan. 1987. p. 84 note 49.
13. Fang Youzhi方有执, Shanghan Lun Tiaobian 伤寒论条辨, 1593. Translation of book title from: Scheid, Volker. 2013. p. 315.
14. Fang Youzhi. 1593. Shanghan Lun Tiaobian 伤寒论条辨, Xueyuan Banshe 学苑版社 2009.p. 11.
15. Scheid, Volker. 2013. p. 331; Wang Xinzhi 王新智. 2008, ‘Fang Youzhi dui shanghan Lun de zhongda de fahui 方有執對《傷寒論》的重大發揮 (Fang Youzhi’s Great Development of the Treatise of Cold Damage), Fujian zhongyi xueyuan xuebao 福建中醫學院學報 (Journal of Fujian University of Chinese Medicine), 18 (5): 53–4.
16. For more on the influence of Fang Youzhi’s book on Qing dynasty physicians see: Ye Fazheng 葉發正. History of Cold Damage Disorders Scholarship 傷寒學術史. Hubei: Huazhong shifan daxue chubanshe, 1995. P. 90-93; Scheid, Volker. 2013. P. 299–360.
17. Scheid, Volker. 2013. P. 336
18. Translation in Ibid. p. 337
19. Translation in Ibid. p. 342
20. Elman, Benjamin A. On Their Own Terms: Science in China, 1550-1900. Cambridge, Mass: Harvard University Press, 2005. P. 107-132.