Jing Fang

Jing Fang built the most fully worked out of the Han systems that tie the Book of Changes to the movement of time. Four hexagrams were set aside to govern the solstices and the equinoxes, and the remaining sixty were distributed across the days of the year, each holding the position for a fixed span, so that any given day had a hexagram and any hexagram had a season. On top of that he arranged the sixty four into eight palaces, one for each trigram, generated by changing the lines of a governing hexagram in a fixed order, which turned the set from a list into a system with an internal logic.

The third component is the one that survived. Under the method called na jia, the ten heavenly stems and the twelve earthly branches are attached to the individual lines of a hexagram, which gives every line an element, a direction and a place in the sexagenary cycle. That is what allows a diviner to read a changing line as a specific relationship in time rather than as a general image, and it is the technical basis of the coin divination method still practised as Liu Yao. A practitioner today casting three coins six times is using an apparatus assembled in the first century BCE.

None of this was fortune telling in the modern sense. Han specialists understood the arrangement as a description of how the year actually works, so that reading a hexagram meant reading the state of the world at a particular moment rather than consulting an oracle about a private matter. The technical apparatus outlived the cosmology that justified it, which is why a system built to model the seasons is now used almost entirely for personal questions.

The tuning problem Jing Fang attacked is an old one and has no clean solution. Stack twelve perfect fifths and you arrive slightly above the octave you started from, by an amount small enough to ignore in practice and impossible to remove in theory. His response was to keep going, dividing the octave into sixty steps in pursuit of a point at which the cycle would close, and although it does not close, the calculation is a serious piece of mathematics and it was done in the service of a cosmological conviction rather than a musical one. In Han thought pitch, calendar and government are the same order expressed three ways, and a tuning that failed to close was a flaw in the world, not in an instrument.

That conviction is also what killed him. If irregularities in the heavens and in the weather report on the conduct of the ruler, then a specialist who can read them has a political weapon, and he used it, submitting memorials that interpreted portents as criticism of the court and of powerful officials. The weapon works both ways. He was accused in turn, his own predictions were used against him, and he was executed in 37 BCE. The atlas notes the case because it shows what correlative cosmology meant in practice: not a private symbolism but a public argument with consequences.