The five phases

The five phases are wood, fire, earth, metal and water. The WHO’s International Standard Terminologies on Traditional Medicine in the Western Pacific Region (2007) defines five phase theory as one of the philosophical theories of ancient China, concerning the composition and evolution of the physical universe, which serves Chinese medicine as “the guiding ideology and methodology of physiology, pathology, clinical diagnosis and treatment”. The theory sorts phenomena into five categories and links the categories by two cycles: in one each phase engenders the next, and in the other each phase restrains another. Acupuncture puts the cycles to work in point selection. The five transport points below each elbow and knee carry a phase each, and a rule from the Nanjing, the Classic of Difficult Issues, chooses among them by the engendering cycle.

Phases rather than elements

The WHO terminology gives “five elements” as another name, and Britannica’s entry on wuxing lists “five-element theory” among its own. The terminology’s preferred term is five phases, defined as “wood, fire, earth, metal and water, and their movements and changes”. The oldest description Robin Wang cites in the Internet Encyclopedia of Philosophy, from the “Great Plan” chapter of the Classic of Documents, already describes each by what it does: water soaks and descends, fire blazes and ascends, wood curves or is straight, metal obeys and changes, and earth takes seeds and gives crops.

From cosmology to medicine

Britannica traces wuxing to a moral theory associated with Zisi, the grandson of Confucius, and with Mencius. In the 3rd century BCE the cosmologist Zou Yan made it a systematic cosmology that “was to dominate the intellectual world of the Han dynasty (206 BCE–220 CE)”, in which the phases overcome and succeed one another in a fixed cycle and are correlated with the cardinal directions, seasons, colours, musical tones and organs of the body. Zou Yan was the first to read dynastic history through the cycle, and Britannica’s biography of him attributes to him the joining of the five phases to the doctrine of yinyang, covered in Yin and yang. By the Han, Wang writes, the two had fused into a single yinyang wuxing teaching, applied to astronomy and the divinatory arts.

Medicine drew on the same body of thought. Richard Bertschinger, introducing his translation of passages from the Huangdi Neijing, describes the Han scholars who assembled its Suwen, or Basic Questions, developing yinyang and wuxing thinking to categorise and synthesise all their data.

What each phase gathers

The WHO terminology defines each phase by the season, colour, taste and pair of organs associated with it. Elsewhere it names the sense organ each zang organ “opens into”, and among the seven emotions it says which organ’s qi each damages in excess. The table assembles those definitions.

The channels take the phase of their organ. The channel system, counted gives the phase of each, including fire for the pericardium and triple burner channels, and The zang-fu organs describes what the theory says the organs in the table do.

Two cycles and how they fail

In the engendering cycle (sheng, 生) each phase gives rise to or promotes the next: wood engenders fire, fire engenders earth, earth engenders metal, metal engenders water, and water engenders wood. In the restraining cycle (ke, 克) each phase checks the phase two steps on: wood restrains earth, earth restrains water, water restrains fire, fire restrains metal, and metal restrains wood. The WHO terminology calls the engendering phase the mother and the engendered phase the child, and describes the two cycles together as what maintains “a relative balance and normal coordination” among the five.

Disease, in the theory, runs along the same lines in the wrong measure or the wrong direction. The WHO terminology names three ways:

• Overwhelming (cheng, 乘), also called over-acting: restraint that is abnormally severe but follows the normal sequence, as when wood restrains earth too hard;
• Rebellion (wu, 侮), also called insulting: restraint that runs opposite to the normal sequence, as when earth restrains wood;
• Mother and child affecting each other (母子相及): a disorder passing from a phase to the phase it engenders or to the phase that engenders it.

Read through the table, wood overwhelming earth is the liver acting on the spleen, and a disorder passing from mother to child is, for example, one moving from the kidney (water) to the liver (wood).

How the phases choose points

The WHO terminology defines five phase points as “a series of five acupuncture points below the elbow or knee on each of twelve meridians, associated with the five phases theory”. They are the well, spring, stream, river and sea points that The five transport points describes. Because each channel also has a phase, every channel holds a point of its own phase, a point of the phase that engenders it and a point of the phase it engenders.

The rule that uses them comes from the 69th issue of the Nanjing, which Park and Kim quote in a 2015 review of Korean Saam acupuncture: “In the case of depletion, fill the respective mother, in the case of repletion, drain the respective child.” The WHO terminology records it as the mother-supplementing child-draining method, in which the mother-child relation is worked out from the phase of the channel and of the point, and points are chosen by reinforcing the mother in deficiency and reducing the child in excess. Park and Kim credit Gao Wu, writing in 1519 under the Ming dynasty, with the first use of the rule on a channel’s own points. Zhang Shixian extended it to points on other channels, and Saam acupuncture, set out in a Korean manuscript they date to between 1644 and 1742, added the restraining cycle; the WHO terminology lists Saam as a school characterised by the five phases and the mother-child principle.

Park and Kim’s worked example is a deficient lung channel, which belongs to metal. Earth engenders metal, so the earth points are reinforced: the lung channel’s own earth point, LU09 (Taiyuan), and the earth point of the spleen channel, SP03 (Taibai). Fire restrains metal, so the fire points are reduced: LU10 (Yuji) and, on the heart channel, HT08 (Shaofu). For an excess of the lung channel the logic reverses: fire is reinforced at LU10 and HT08, and water, the child of metal, is reduced at LU05 (Chize) and, on the kidney channel, KD10 (Yingu).

What research has tested

Saam acupuncture has been tested in a small randomised trial. A 2022 feasibility trial by Boram Lee and colleagues at the Korea Institute of Oriental Medicine assigned 24 people with functional dyspepsia, indigestion that meets the Rome III diagnostic criteria, to Saam acupuncture three times a week for four weeks alongside usual care, or to usual care alone. At four weeks the groups did not differ on the dyspepsia symptom scores; they differed at the follow-up assessments at eight and twelve weeks, and the authors call for a larger confirmatory trial. A comparison with usual care cannot separate the effect of choosing points by the five phases from the effect of being needled at all; Sham acupuncture covers the controls that try to.

What the sources cannot tell you

The correspondences in the table are the set the WHO terminology standardised in 2007. Britannica’s account places the theory’s first uses in moral philosophy and dynastic history, so the medical set is one application among several. AcuiQ records which points a study prescribed, not why. A published prescription that includes LU09 for a lung complaint may have been built on the mother-child rule or on some other reasoning, and the entry does not say which.