Wu Xing

What holds the five phases together is not the list but the two orders in which they are said to succeed one another. In the generating order, wood feeds fire, fire leaves ash and so makes earth, earth yields metal, metal gathers water, and water nourishes wood. In the overcoming order, wood breaks earth, earth dams water, water quenches fire, fire melts metal, and metal cuts wood.

Each cycle is a closed loop of five, and every phase therefore stands in a fixed relation to every other: it generates one, is generated by one, overcomes one and is overcome by one. That gives the scheme its analytical power. A situation described in terms of the five phases is not merely classified, it is placed in a set of relations that says what will strengthen it and what will check it, and both cycles are needed for that. A scheme of generation alone would run away with itself.

The word usually rendered element in English is xing, which means going, moving or conduct rather than substance. Water in this system is not the liquid but the phase of gathering, sinking and cold that the liquid exemplifies. Joseph Needham argued that translating xing as element imported a Greek assumption about matter that the Chinese scheme does not make, and preferred phase for exactly that reason. The atlas follows the same usage.

The five appear as a bare list in the Great Plan chapter of the Book of Documents, with no cycles and no correspondences attached. What turned that list into a system was the work of the Warring States and Han periods, when thinkers associated with the school of yin, yang and the five phases, Zou Yan chief among them by later report, matched the five to directions, seasons, colours, tastes, planets, organs, numbers and the succession of dynasties. Under the Han, Dong Zhongshu built the resulting scheme into a political theology in which the conduct of the ruler and the condition of the natural world answered to one another.

Joseph Needham called this way of reasoning correlative thinking, and his second volume on the history of scientific thought in China remains the fullest account of it in English. Its logic is not causal in the sense a modern laboratory would recognise. Things in the same category resonate, and a change in one register shows up in another because they belong together, not because one pushed the other.

The dynastic use is the sharpest example. A ruling house claimed a phase, and the phase that overcame or generated it determined which house could legitimately follow. Cosmology and succession were one argument. That is why the scheme survived as the organising frame of Chinese medicine, divination, music theory, statecraft and the calendar rather than as one theory among several: it was the shared grammar in which claims in all of those fields were made.