Numerology and Chinese medicine

The texts of classical Chinese medicine testify to creative tensions between numerical continuities with the ancient world and changing conceptions of the human body as they relate to medical practice. They draw on number-related clues to understanding innovation, in the way they draw on, systematise and pluralise the earlier numerical traditions described in Part I. The Huangdi neijing 黃帝內經 (Yellow Emperor’s Inner Canon), the locus classicus of classical Chinese Medicine, is a selection of different texts and traditions that have accumulated over various centuries. This has resulted in the received text having an eclectic range of number systems, which have been deployed at different times and for different effects. The Huangdi neijing is in two parts: the Suwen 素問 (Simple Questions) and Lingshu 靈樞 (Numinous Pivot). In 751, Wang Bing 王冰 began his revision of the earlier version of the Suwen, with an emphasis on self-cultivation and the importance of aligning oneself with the movements of the cosmos (Chapter 7 in this volume; Unschuld 2003: 41). His revision of 762 CE included seven extra chapters (Suwen 66–74), ¹ specifically focused on Wuyun liuqi 五運六氣 (Five Movements and Six qi) theory, which he claimed were secret knowledge from earlier times, received as a master-disciple transmission (Ibid.: 46). This new version demonstrates an attempt to order what at first sight might seem like a confusing and fragmentary medieval legacy. Wang Bing’s focus, seen uniquely in his Wuyun liuqi chapters, reflects a post-Han view of the imperial cosmos, based on the interplay between the numbers Five and Six. ²

This chapter argues that number sequences provided a structural organisation that was the basis for various arrangements over longer periods of time by introducing innovative arrangements which, nonetheless, seemed to ground these innovations in ancient wisdom. We see in the Wang Bing chapters permutations of all the basic numbers sequences introduced chronologically in Part I, beginning with One, and the identification of qi as the unifying factor (Yang 1997: 56–7). Human life, itself an expression of the merging of the duality of Earth/yin and Heaven/yang, was animated by qi, the vitality of life.

陰陽者，天地之道也，萬物之綱紀，變化之父母，生殺之本始

Yin and yang are the way of Heaven and Earth, the rule and order of the myriad beings, the mother and father of change and transformation, the beginning and end of life and death.

(Suwen 5, 2.61) ³

The totality of an ideal human lifespan is discussed in the first chapter of the Suwen: life was presented therein as dependent on a finite amount of essence (jing 精) allotted at birth and gifted by Heaven. This essence was the basis of the growth and development of the human body according to seven- and eight-year periods: men were thought to follow a cycle of eight years, while women followed a seven-year cycle. Human life was in constant interaction between Heaven and Earth, following underlying numerological cycles. The rubric of Four (or doubled here to make the Eight of the male cycle) had been a basic design following the Four directions and the seasons since Shang times. The rubric of Seven appears here as the female cycle but is less pervasive throughout classical medicine as an organising principle, and perhaps reflects a period before gender difference was clearly and consistently articulated as a feature of medicine (Chapter 23 in this volume).

Thereafter, the numerological organisation of the chapters Suwen 2, Suwen 4 and Suwen 5 ⁴ turns to elaborating correspondences that structure human health and the body to the Four seasons and also to the Five Agents (wuxing): these numbers structure direction, colour, taste, organ, orifice, animal, planet, etc., through a new integration of the old rubrics of Four and Five. This was a shift from the early Shang idea of Four directions to a more integrated imperial view of the cosmos based on Five, identified as ‘correlative cosmology’ in the secondary literature (Henderson 1984; Graham 1986; Wang 2000).

Microcosm and macrocosm

The Five Agents interacted in different ways, following cycles of ‘mutual conquest’ (xiangke 相剋 or xiangsheng 相勝) and of ‘mutual generation’ (xiangsheng 相生). The earliest introduction and use of Five Agents as an interpretive structure that we know is evident in the ‘conquest’ cycle: a cycle that regularised the succession of dynasties and their regime change by giving the conquering rulers a cosmological legitimacy. The advice to (mythical) rulers was to devise rituals associated with their ruling Agent, using the colours associated with their Agent, and interpreting omens accordingly (Loewe 2005: 152–4).

When an emperor or king is about to arise, Heaven must first manifest good omens to the people below. At the time of the Yellow Emperor, Heaven first caused giant mole crickets and earthworms to appear. The Yellow Emperor announced ‘the qi of Earth is victorious’. Since the qi of Earth was victorious, he valued the yellow colour and used Earth as a rule for his affairs.

(Lüshi chunqiu, 13.2, 284) ⁵

The ‘Great Plan’ (Hongfan 洪範) chapter of the Shujing ⁶ lists the Agents following the conquest or control cycle sequence.

Five Agents: the first is Water; the second is Fire; the third, Wood; the fourth, Metal; and the fifth, Earth.

(Shujing, 12.357)

The conquest cycle was a strong feature of the daybooks ⁷ or almanacs (rishu 日書) and other divinatory texts of the Han (Liu 1994: 434; Li 2000a: 131; Harper and Kalinowski 2017: 169). Reflecting relationships of control and violence, the conquest cycle first structured divinations used for the purposes of government and warfare.

The virtue (of the ruler) is only from good government, good government nourishes the people. This comes only by studying Water, Fire, Metal, Wood, Earth, and grains.

(Shujing, 4.106)

In contrast, the xiangsheng 相生 (mutual generation) cycle, that was to become so important to imperial medical theory, was virtually absent from the daybooks and this contemporary evidence allows us to imagine a chronology for the numerical sequences (Harper and Kalinowski 2017: 169). The xiangsheng cycle, one indicating nourishment or support, like a mother to a son, was expressed in Dong Zhongshu’s 董仲舒 (ca. 179–104 BCE) Chunqiu fanlu 春秋繁露 (Luxuriant Dew of the Spring and Autumn Annals), a text of the Western Han (202 BCE–9 CE) period, which consolidated Five Agent theory to uphold Dong’s theory that humans should follow the cycles of the heavens closely and look to the lessons of the past for guidance, especially the hierarchies of social relationships at the basis of the traditions of Kongzi 孔子 (Confucius). The emergence of the xiangsheng cycle is a clear reflection of the work of Han scholars in whose interests it was to promote the new imperial priorities of unification, rather than conflict.

Wood gives birth to Fire, Fire gives birth to Earth, Earth gives birth to Metal, Metal gives birth to Water, these are father and son.

(Chunqiu fanlu, 38.315) ⁸

The change in focus from ke/control to sheng/nourishing imitated the ‘Great Plan’, but followed the order of generation instead of conquest:

Heaven has Five Agents: the first is Wood, the second is Fire, the third is Earth, the fourth is Metal, the fifth is Water. Wood is the beginning of the Five Agents; Water is the end of the Five Agents. These are the sequence of Heaven’s order.

(Chunqiu fanlu, 42.320) ⁹

The Chunqiu fanlu also gave the correlations and qualities of the Five Agent cycle of generation, relating each Agent to a direction and season: except Earth, which was placed in the centre, establishing its special relationship to Heaven.

Therefore Wood resides in the Eastern direction and rules spring qi, Fire resides in the Southern direction and rules summer qi, Metal resides in the Western direction and rules autumn qi, Water resides in the Northern direction and rules winter qi […] Earth resides in the centre, it acts as the enrichment of Heaven. As for Earth, it is Heaven’s trusted aide.

(Chunqiu fanlu, 42.322) ¹⁰

The early chapters of the Suwen mention both the conquest and generation cycles, but more emphasis is put on the harmonious cycle of life, the growth and regeneration cycle: spring gives birth to summer, just as Wood and the liver give birth to Fire and the heart.

The East generates Wind; Wind generates Wood; Wood generates sour [flavour]; sour [flavour] generates the liver; the liver generates the sinews; the sinews [representing East/Wind/Wood] generate the heart.

(Suwen, 2.67) ¹¹

This transition from a cosmological polity numerically modelled on the dynamics of warfare and violent control to one of harmonious central imperial governments reflects the priorities of the new administration in medical terms. Suwen 8 ¹² introduces the twelve organs (zang 臟, the yin storage organs or ‘viscera’; and fu 腑, the yang transporting organs or ‘storehouses’) as homologous with the collaborative hierarchy of the Emperor and his court officials. Medicine, in this way, echoed the transition from the final decades of the Warring States to the new forms of government of Qin (221–206 BCE) and Han (202 BCE–220 CE) – shifting focus from the conquest to the generation cycle. This centralised government relied on a strong bureaucratic hierarchy to mediate between the Emperor and his people (Unschuld 2003: 325–6).

The heart holds the office of sovereign, the radiance of the spirits stems from it. The lungs hold the office of chancellor, regulating rhythms stems from it. The liver holds the office of general, conception of plans stems from it.

(Suwen, 3.93) ¹³

The reflection between human beings and their environment was emphasised in Suwen 3, Suwen 6 and Suwen 9, which discuss the notion of Six. Six in the macrocosm were the Six climates or Six qi (liuqi 六氣 (Chapter 4 in this volume), which in the human form corresponded to the liujing 六經, the Six Channels (jing 經 hereafter body ‘Channels’). In this way, the human body became a microcosm of the environment and each Channel was thought to respond to its associated climate, qi (Yang 1997: 64–9) (Table 5.1).

This meteorological body thus began to map the ideal harmony between human anatomy and physiology against changes in the external environment, in terms of the combination of Six Channels and Five Agents (Chapter 2 in this volume). While the combination of Five and Six had been a foundational concept first emphasised in the Warring States text, the Zuozhuan, ¹⁴ then systematised in the Han medicine of the Huangdi neijing – these numbers were then combined in innovative ways in the interpolated chapters of Wuyun liuqi theory – written more than half a millennium later than the rest of the Huangdi neijing material.

Four and Five in classical medicine

Number systems were neither exclusive nor fixed in practice. Different systems co-existed, and the aligning of plural numerological theories responded to both political expediencies and the practicalities of medicine. This plurality in the use of numbers facilitated continuity, even as different systems generated one set of numerical combinations from another.

In the body, the fundamental significance of Four was represented by the Four limbs, dependent on the centre, the trunk; similarly, the Four lands of the Shang of the ancient world had been defined from their centre, the residence of the Shang king. In ritual texts, Four easily became the basis of Five: Four with their intersection, the centre. The increasing systematisation in the medicine of the Huangdi neijing highlighted a fundamental tension between the priority of Four and Five in early imperial Chinese numerology. This tension was to play out in the Yellow Emperor corpus through the spatio-temporal characteristics of the Five Agents, through the position allotted to the agent of Earth; it first emerged in the discourse of auspicious days in the daybooks (Liu 1994: 435; Li 2006a: 303) and was later systematised in Suwen 4 and Suwen 5.

The calendar provided the cosmological framework (Harper and Kalinowski 2017: 153) which marked time and space in an integration that was codified in the ‘cord-hook diagram’ (二繩四鉤圖 ersheng sigou tu – literally the ‘two cords and four hooks’ diagram; Li 2006b: 91–105; Li 2006a: 74, 84, 316; Harper and Kalinowski 2017: 162–9). This diagram is the basis for many divinatory systems and the locus classicus for its definition is found in the astronomical chapter of the Han dynasty Huainanzi 淮南子 (Masters from Huainan, compiled 139 BCE). ¹⁵ The rubric of Four is present in the two ‘cords’ marking the North-South and East-West axes, which also represents the summer-winter solstices and the spring-autumn equinoxes, respectively (Li 2000b: 131, 163; Li 2006b: 69–85). The Branches of the Shang calendar (Chapter 4 in this volume) in the quotation that follows serve to plot the seasons onto the diagram:

Ziwu [b1 and b7], maoyou [b4 and b10] are two cords, Chouyin [b2 and b3], chensi [b5 and b6], weishen [b8 and b9], xuhai [b11 and b12] are four hooks.

(Huainanzi, 3.207) ¹⁶

The twelve calendrical Branches, represented by the ‘b’s on the diagram, were evenly spaced around the outside of the cord-hook diagram (b1–b12), each Branch representing a lunar month. Four of these Branches, (b1, b7) and (b4, b10), plotted the ends of the two cords, which also formed a central cross of the vertical and horizontal axes. These four Branches at the North, South, East and West of the diagram were the lunar months containing the two solstices and two equinoxes, representing the midpoint of each of the Four seasons on the four sides of the diagram (Yang 1997: 59–61). Each season plotted three Branches along one side: the solstices and equinoxes in the four directions and the two Branches placed either side of these. The two Branches either side of the solstices and equinoxes were then connected by a right-angled line to the previous or next seasons linking across the corners of the diagram. These right-angled corners of the diagram were the four ‘hooks’.

The Stems (s1–s10) add a further dimension to the Four directions, spatial markers that were arranged around the cord-hook diagram just inside these outer seasonal arrangements (Liu 1994: 434; Yang 1997: 252). The ten Stems, unlike the twelve Branches, had an Earth/central component: two Stems (s5 and s6) were placed in the centre (Liu 1994: 159), next to the intersection of the two cords, emphasising the Fifth dimension of the Centre (see Figure 5.1).

This interweaving of Four and Five in the two cords and four hooks design can therefore be interpreted as defining ‘spatio-temporal spaces’ (Li 2000b: 162–4). The daybooks, in particular, allow us to see critical points at which the Five Agents were refined and standardised from pre-existing correlative systems (Liu 1994: 283, 346–7, 431–40; Li 2006b: 156–171). By the end of the Warring States (475–220 BCE), the Five Agents had, in this way, been used extensively to construct daybooks and divinatory schemes (Harper and Kalinowski 2017: 171).

Where Five Agents were primarily an indication of powers located spatially and directionally, through this process, they became increasingly associated with the passage of time. The calendar, its seasons and months, was thereby enshrined in the late Warring States ritual texts that were not only a feature of everyday life, but also guided the Emperor’s behaviour – in this case according to a ritual calendar (the Monthly Ordinances, yueling 月令 in the Lüshi Chunqiu). It was largely this temporal organisation that provided the basis for the calendar’s incorporation into medical practice (Liu 1994: 416; Li 2006a: 62–72).

However, the persistent prevalence of the rubric Four, perhaps more naturally manifest in the cardinal directions and four distinct seasons of North China had to be reconciled with the Five of the Five Agents, which had an overarching political imperative. This was accomplished by dividing the summer season in two, making a fifth season, Late Summer (changxia 長夏). The attempt at reconciling potentially conflicting ritual sequences, through adding the Late Summer sequence in time, is first evident in Book Six of the ritual almanacs of the Lüshi Chunqiu – an eclectic text, tellingly compiled by Lü Buwei 呂不韋, advisor to King Zheng of Qin the first Emperor of China-to-be (and possibly, according to Sima Qian, his father). The Central Region was, in this text that heralded the rise of the Five Agents, as emblematic of imperial unity, summarily appended to the description of the last month of summer, creating a special fifth season, related to Earth (Knoblock and Riegel 2000: 152–6). In texts such as the Huainanzi and the Chunqiu fanlu of the mid-Western Han period, the Earth (tu 土) was no longer the Centre but just one sequence in the generative cycle of the Five Agents, just as the ritual centre was regularised as part of an integrated spatial unity of empire itself. ¹⁷ Nevertheless, there remained a creative tension between the two rubrics of Four and Five.

The Five Agents, the Four directions and their intersection, the Centre, symbolised all possible movements of life: their effects on the body were described in Suwen 4 and Suwen 5. Here are the correspondences with the Agent Metal from Suwen 5:

The West generates Dryness; Dryness generates Metal; Metal generates acrid [flavour]; acrid generates the lungs, the lungs generate skin and body hair […] These in Heaven are Dryness, on Earth are Metal, in the body are skin and body hair, among the zang [organs] it is the lung; among the colours it is white; among the tones it is shang; among the sounds it is weeping; among the transformations it is coughing; among the orifices it is the nose; among the flavours it is acrid; among the states of mind it is sorrow.

(Suwen, 2.71) ¹⁸

Over the course of the Han dynasty, in texts applying the Five Agents as the framework for all patterns of the cosmos, such as the Chunqiu fanlu, while Earth was just one of the Five Agents, it often retained its temporal significance as Late Summer and was emphasised as the most important Agent.

As for Earth, it is the son of Fire. Among the wuxing there is none as valuable as Earth.

(Chunqiu fanlu, 38.316) ¹⁹

In later discussions, however, immortalised in the Baihutong delun 白虎通德論 (‘The Virtuous Discussions of the White Tiger Hall’, ²⁰ 58 CE – a treatise on politics and philosophy keyed to cosmological ideas such as Five Agents and yin-yang), the cosmos was seen as ordered and symmetrical through the alternation of the Four seasons, and thus incompatible with Earth as a discrete fifth phase. Emphasis on the role of the Earth was as an intermediary place of transformation from each season to the next, so it was allotted an eighteen-day period at the end of each of the Four seasons. This mediating role can be seen in early Han astrolabe shi instruments for divination. The Earth-related Stems (s5, s6) were no longer placed in the centre, as in the cord-hook diagram, but were in the four corners. These became the ‘four gates’ simen 四門 – see Figure 5.2 – the four diagonals radiating out from the centre (North-East, North-West, South-East and South-West) enabling a smooth transition from one season to the next (Harper and Kalinowski 2017: 163).

The flexibility which the rubrics of numbers Four and Five maintained throughout the early empires was to endow medical theory with an enduring plasticity that was critical to Wang Bing’s calculations in his new interpretations of classical medicine in the Tang period (618–907).

Five and Six in medieval medicine

Central to Wang Bing’s medieval additions to the classical tradition was a systematisation of the rubrics of Five and Six as embedded in the Wuyun liuqi chapters. His attempt to integrate these numerological traditions was not new. It was a Tang systematisation of earlier solutions to numerical disagreements about the total number of organs and channels in the body.

Wuyun Liuqi 五運六氣 (Five Circuits 36 and Six qi): the integration of the numbers Five and Six

Wuyun liuqi was a legacy of the intertwining of divination and medicine in China: incorporating many aspects of the astro-calendrical divinatory systems, based on Five and Six (Porkert 1974: 55–106; Ren 1982; Fang and Xu 1984; Unschuld 1985: 170–1; Liu 1990; Despeux 2001: 121–65; Unschuld 2003: 385–494). Scholars studying the Song dynasty consider this doctrine as one of the more significant intellectual changes (Goldschmidt 2009: 183). These chapters were a complex map of the movements of Heaven and Earth designed to predict seasonal imbalances: if the cosmos moved according to Wuyun liuqi, then the body, as a mirror of the macrocosm, would adjust itself accordingly to maintain health, by alignment with the prevailing climates (Goldschmidt 2009: 83). Weather prediction, keyed to the calendar, provided a yardstick to measure whether the seasons and associated climates would come too early, or too late, either of which could be the cause of disease and impel its aetiological processes (Hinrichs 2003: 140). These seven chapters provided a method to establish normative physiological and cosmic cycles in order to diagnose seasonally related illnesses: they offered the hope of prediction, which could lead to the control of devastating anomalies such as epidemics (Unschuld 1985: 141).

The interplay between Five and Six was embodied in the terminology used in the Wang Bing chapters: ‘Five Circuits’ (wuyun 五運) and ‘Six qi’ (liuqi 六氣). The Stem and Branch of a year (an ancient calendrical example of the combination of Five and Six) ³⁷ gave the overall climate for the year which would then vary predictably according to Wang Bing’s innovations (Yang 1997: 794–7). Each year was then further divided into smaller seasons: a series of five seasons, known as the five host Circuits (zhuyun 主運) ³⁸ and a series of six seasons, known as the six host qi (zhuqi 主氣). ³⁹ The Five host Circuits and the Six Host qi followed the expected seasonal climates occurring at set dates: Wind in spring, Cold in winter, etc. To allow for the considerable climatic variation within each season, there were also guests (ke 客). These guest Circuits and guest qi spanned the same time periods as the host Circuits and qi (Yang 1997: 797–800). The relationships between an unchanging host and a variable guest were interpreted through the generating and conquest cycles of Five Agents, introducing further flexibility in the potential to predict climatic variation for the year. ⁴⁰

The concept of Five Circuits is specific to the Wuyun liuqi chapters, and has some parallels with Five Agents, but refers to a symbolic system keyed specifically to the movements of the Heavenly bodies (sun and moon, constellations and planets), and used uniquely to determine climatic and physiological anomalies. Suwen 67 matched the Five Circuits to the Five Agents by repeating exactly the same relationships from Suwen 5 where it is stated that, for example:

The Southern direction generates Heat, Heat generates Fire, Fire generates bitter, bitter generates the heart (Suwen, 2.68–70; 19.539–41). ⁴¹

This parallel emphasised their essential similarity, and provided the normative state, since the Circuits from Heaven ⁴² were harmonised with those of the human body through the resonance of the Agents. ⁴³

Suwen 69 listed the climates expected in each year of the sexagenary cycle. ⁴⁴ A particular year would be associated with one of the Five yang Great Circuits ⁴⁵ (active or excess, taiguo 太過), or one of the Five yin Great Circuits (passive or insufficient, buji 不及) and a tendency towards particular pathologies (Unschuld 2003: 410).

Search for the [season’s] arrival […] when it is not yet [expected] to arrive but arrives, this is called taiguo [excessive] when it is [expected] to arrive but does not arrive, this is called buji [insufficient].

(Suwen, 3.103–4) ⁴⁶

If a year had an active Great Circuit, then the qi associated with that Circuit was expected to manifest itself violently, giving an excess of the associated climate. During Earth active Great Circuit years, for example, one would have to be vigilant against diseases of Dampness and cold. If it was a year with a passive Great Circuit, then the climate associated with that Circuit was weak. During Earth passive Great Circuit years, one would have to be vigilant against diseases of excess Wind (Ibid.: 409). The active or passive actions of a Great Circuit applied the conquest cycle of the Five Agents to predict the expected climate of the entire year. Further spatio-temporal flexibility was introduced through grouping the Branches in different ways according to their seasonal relationships or according to cycles of climatic change following the cycles of the Six qi.

The core Wang Bing chapters, especially Suwen chapters 71 and 74, provide exhaustive tables with which a physician could predict the disease profile of a particular year. ⁴⁷ To do that, he would have to have specialised training to interpret the quality of an individual year and all its shorter (Five and Six) seasons. All these predictions were prefaced on innovative arrangements of the rubrics of Five and Six, as understood in their relations to the xiangsheng and xiangke cycles of generation and control.

Practical applications of Wuyun liuqi

The cyclical flow of Heaven (space: sun, moon, stars) and Earth (time: seasons, day/night) created and maintained the constantly changing climates, the sphere of human existence (Unschuld 2003: 393). Wuyun liuqi was an attempt to order what seemed to be in disorder: the occurrence and duration of different climates, following a sexagenary cycle. Huangdi neijing and Wuyun liuqi theory was based on the premise that climates were the root of disease, and humans could maintain health by adapting to their climatic environment (Yang 1997: 801–2). Climate prediction allowed humans to integrate themselves in their environment, thus following the natural laws of Heaven and Earth to maintain their health (Unschuld 2003: 394).

Hence as for yin-yang and the four seasons, they are the end and beginning of the myriad beings, the root of life and death; if you oppose [them] then there is disaster and harm to life, if you follow then severe illness will not arise, this is called to obtain the way.

(Suwen, 1.39–40) ⁴⁸

A map of future climatic variations was important for the prevention of disease (Unschuld 2003: 335) and as advance warning for too much of one particular climate, which could precipitate disease. Climate prediction acted as a standard against which to measure any variations (unseasonal climates), which caused disease especially in people who were unable to adapt to it sufficiently, as they were already depleted.

The overall rule for treatment was to adapt to, or counteract the effect of, the predominant climates calculated according to the specific climatic predictions of that year (Suwen 69, 71, 74). If these predicted climates were overwhelming, they could attack the body, so the overwhelming climatic qi needed to be calmed and cleared from the body. If the climatic qi were weak, the body’s qi could be strengthened to oppose any pathological influences.

For each [instance of unruly climate] pacify its qi, clear and calm it; then disease qi declines and leaves, returning to its place of origin; these are cardinal principles of treatment.

(Suwen, 22.736) ⁴⁹

Suwen 74 lists pathological indicators for the whole year and seasons (Circuits and qi) of the year, with expected illnesses, ending with some basic rules for herbal medicine, finally exhorting the practitioner to focus on the underlying cause which, we can only assume, could be found by fully applying Wuyun liuqi theory.

The culmination of the iatromancy inherent in Wuyun liuqi theory may not have had many clinical applications until the Song dynasty (960–1279), three centuries after Wang Bing devised the theories (Despeux 2001: 129), when it came to prominence along with renewed interest in cosmology (Hanson 2008: 344). The physician Pang Anshi 龐安時 (1042–1099) author of ‘Discussions on Cold Damage and general disorders’ (Shanghan zongbing lun 傷寒總病論) incorporated Wuyun liuqi into Cold Damage theory (Chapters 4 and 8 in this volume) (Hinrichs 2003: 110). Both Wuyun liuqi and Cold Damage theories drew on the Six qi, and predicted the source and course of a disease based on unseasonable climates: so together they could be used to predict and treat the epidemics which plagued the dynasty (Hinrichs and Barnes 2013: 114). In 1099, the Director of Studies of the Imperial Medical Service, Liu Wenshu 劉溫舒 (late eleventh century), presented his ‘Discussion of the esoterica of the circulatory phases and the seasonal qi as formalised in the Suwen’ (Suwen rushi yunqi lun’ao 素問入式運氣論奥) ⁵⁰ claiming that each season was dominated by certain climatic influences that inevitably caused certain illnesses. Liu explained Wuyun liuqi in detail, its application to physiology, pathology, diagnosis, treatment and the integrated use of medicinals: it was the first step in applying Wuyun liuqi theory to medicine as a whole (Goldschmidt 2009: 184).