Nuclear, inverse and opposite hexagrams: the hidden structure of a reading

A hexagram is never alone. Rearrange its lines and three related figures appear, each used by commentators since the Han dynasty to say something the main text leaves unsaid. The Chinese phrase 錯綜複雜, "intricate and complex", literally names two of them. Here is what they are, how to derive them by hand, and what to do with them. Every page in our reading room lists all three with links.

The nuclear hexagram (互卦, hugua)

Take lines 2, 3 and 4 of a hexagram as a new lower trigram, and lines 3, 4 and 5 as a new upper trigram. The six-line figure they form is the nuclear hexagram — the hexagram hidden in the middle, sharing the four central lines.

Example: Hexagram 3, Zhun is 010001 (bottom to top). Lines 2–4 are 100 (☶ Gen), lines 3–5 are 000 (☷ Kun): the nuclear hexagram is Gen over Kun, Hexagram 23, Bo. Inside "difficulty at the beginning" sits "splitting apart" — the sprout must break the ground.

Tradition reads the nuclear hexagram as the inner situation or tendency: what is developing beneath the surface, the matter's core. Because the two central trigrams overlap, only sixteen hexagrams can be nuclear, and the nuclear of a nuclear always lands on one of four — Qian, Kun, Jiji or Weiji. Readers take this as a picture of how every situation reduces, at its core, to creation, reception, completion or incompletion.

The inverse hexagram (綜卦, zonggua)

Turn the hexagram upside down — read the lines from top to bottom — and you have its inverse (also "reversed" or "overturned"). This is how the received text is organised: the sixty-four hexagrams come in pairs, and in most pairs the second is the first turned over. Zhun (3) upside down is Meng (4); Tai (11) upside down is Pi (12).

The inverse is the same situation seen from the other side — the other party's view, or what the situation becomes when the roles reverse. Eight hexagrams look the same upside down (Qian, Kun, Yi 27, Daguo 28, Kan, Li, Zhongfu 61, Xiaoguo 62); their pair partner is instead their opposite.

The opposite hexagram (錯卦, cuogua)

Change every line — yin to yang, yang to yin — and you have the opposite (also "complementary" or "lateral"). Qian's opposite is Kun; Zhun's opposite is Hexagram 50, Ding: the raw sprout against the finished cauldron.

The opposite describes what the situation is not — the counterweight, the missing quality, sometimes the remedy. Readers who find a hexagram one-sided look at its opposite for balance.

The changed hexagram, for comparison

These three are structural: fixed for each hexagram, the same in every reading. The changed hexagram (之卦) is different — it depends on which lines were cast as moving, and it is part of the verdict rather than the background. See changing lines.

How much weight to give them

In a reading, the texts come first: Judgment, Image, moving lines. The structural hexagrams are commentary you add when the main text is clear and you want depth, or when it is obscure and you want a second angle. A sensible order:

• Nuclear for the inner dynamic — what is really going on.
• Opposite for what is lacking or needs balancing.
• Inverse for how the other side sees it.

The Han commentators built elaborate systems on these relations; the Song commentators (Zhu Xi among them) warned against letting the structure crowd out the words. Both are right: the structure keeps a reading from being arbitrary, and the words keep it from being mechanical.

Finding them without a table

• Nuclear: write the six lines; copy lines 2–3–4 then 3–4–5.
• Inverse: write the six lines in reverse order.
• Opposite: flip every line.

Then look up the result in the trigram table (upper trigram by row, lower by column). After a few readings you will not need the table.