Ho Peng Yoke

Ho Peng Yoke worked on Chinese science for half a century, collaborated with Joseph Needham on the great survey of Chinese science and civilisation, and later directed the institute at Cambridge that carries Needham name. His book on Chinese mathematical astrology is the reason the atlas can describe several Chinese divinatory systems without relying on practitioner manuals, because it treats them as historical techniques with datable sources, named authors and reconstructible procedures.

The systems it covers are the three that Chinese tradition groups together as the arts of the cosmic boards. Taiyi tracks a supreme unity moving through palaces on a fixed schedule and was used for questions about dynasties and large events. Dunjia works with a set of stems and branches distributed over a board with a shifting arrangement and was applied to military and practical timing. Liuren uses a rotating heaven plate above a fixed earth plate to produce a figure read for the moment of the question. All three were, at various times, restricted knowledge, taught in the state astronomical office and forbidden to private study, because a technique for predicting the fate of a dynasty is a political object as much as a religious one.

The argument that runs underneath this whole field is whether any of it counts as science, and Ho Peng Yoke is cited on both sides of it, which is a sign that he answered carefully. His position was that the categories being applied are modern and Western, and that in their own setting calendar making, astronomy, astrology, medicine and alchemy were not separate enterprises to be sorted into the respectable and the discarded. The same office computed the eclipse and interpreted the omen. The same texts give the mathematics and the meaning. Splitting them retrospectively tells you about the person doing the splitting.

That approach is why he is useful to a reference work rather than only to a specialist. Systems such as Zi Wei Dou Shu, the star chart method that assigns notional stars to twelve palaces derived from a birth time, are served in English mainly by books written to teach the practice, which take the framework as given and do not ask where it came from or when. A historian who describes what practitioners did, in what period, with which texts, and declines to certify or dismiss it, produces material an atlas can use in either direction. The atlas cites him for the history and leaves the verdict where he left it.