The Xugua and Zagua: the I Ching's sequence and contrast commentaries

The Xugua (序卦傳, "Sequence of the Hexagrams") and the Zagua (雜卦傳, "Hexagrams in Irregular Order") are the last two of the Ten Wings. The Xugua walks through all 64 hexagrams in the received order and gives a reason why each one follows the one before; the Zagua sets the hexagrams side by side in pairs and sums each one up in a word or two. Neither tells you how to read a cast, but together they are the best memory aid the tradition offers, and they make the familiar order feel less arbitrary.

What the Xugua does

The Xugua is a chain of small arguments. Its formula is almost always the same: something happens, it cannot go on forever, "therefore it is received by" (故受之以) the next hexagram. It opens with the world itself:

• 有天地，然後萬物生焉 — "There are heaven and earth, and then the myriad things are born." Heaven and earth are Qian and Kun.
• What fills the space between them is the myriad things, so next comes Zhun, Difficulty at the Beginning: 屯者，物之始生也, "Zhun is things being first born."
• 物生必蒙 — things just born are immature, so Meng, Youthful Folly, follows.
• Immature things must be nourished, so Xu, Waiting, whose text the Xugua glosses as "the way of food and drink."
• Food and drink bring disputes, so Song, Conflict; conflict raises the masses, so Shi, the Army.

The same rhythm runs through the whole book. Its most quoted step is the turn from Peace to Standstill: 物不可以終通，故受之以否 — "things cannot be in free flow to the end, so Pi follows." Tai gives way to Pi, and in the next step "things cannot be blocked to the end," so Fellowship comes after. The sequence ends on the most famous line of all: 物不可窮也，故受之以未濟終焉 — "things cannot be exhausted, so it ends with Wei Ji, Before Completion." The book closes on something unfinished.

The second half of the Xugua has its own opening. Instead of restarting with heaven and earth, it builds a social chain: heaven and earth, then the myriad things, then man and woman, husband and wife, father and son, ruler and minister, and finally ritual and right conduct. That leads into Xian, Attraction, and then: "the way of husband and wife cannot but endure, so it is received by Heng," Duration. The division of the book into an upper canon (1–30) and lower canon (31–64), discussed in the guide to the King Wen sequence, is visible right here.

How seriously to take the Xugua

Scholars have long treated the Xugua as one of the thinnest of the Wings. Many of its links are puns: it defines Meng with 蒙 and Bi with 比, using the name to explain the name, and some steps could easily be argued the other way round. It almost certainly explains an order that already existed rather than revealing how the order was made; the Mawangdui silk manuscript arranges the hexagrams quite differently, so the received sequence was not the only one in circulation.

Even so, the Xugua was taken seriously. Cheng Yi opened his commentary on almost every hexagram by quoting it, using it to say what situation the hexagram grows out of. Wilhelm printed the relevant sentences under each hexagram in his third book as "The Sequence." The value is not that the order is proven, but that each hexagram is set in motion: a situation arises from the last one and gives rise to the next. That is a useful habit when you read a cast.

What the Zagua does

The Zagua is shorter and almost poetic: a string of rhymed half-lines that contrast hexagrams two at a time. Its opening reads 乾剛坤柔，比樂師憂 — "Qian is firm, Kun is yielding; Bi is joy, Shi is worry." A few more:

• 損益，盛衰之始也 — Decrease and Increase are the beginnings of flourishing and decline.
• 剝，爛也；復，反也 — Bo is rotting away; Fu is return.
• 否泰，反其類也 — Pi and Tai are opposite in kind.
• 革，去故也；鼎，取新也 — Revolution removes the old; the Cauldron takes up the new.
• 既濟，定也 — After Completion is settled.

Most of these pairs are the same pairs as in the received order, where each hexagram sits next to its inverse or its opposite (see hexagram pairs). But the Zagua shuffles the pairs among themselves, hence its name, and it often gives the shortest definition of a hexagram anywhere in the tradition. Wilhelm translated these too, as "Miscellaneous Notes."

The text also has a puzzle at its end. From Da Guo onward, the last eight hexagrams are not grouped in their usual pairs. Song commentators, Zhu Xi among them, suspected that the bamboo slips had been disordered; others have defended the order as deliberate. The tradition has not settled the question, and you do not need to.

Using them to memorise the sequence

If you want to know the 64 hexagrams by number, the two Wings work well together:

• Learn the pairs first. 32 pairs are far easier to hold than 64 items, and the Zagua's two-word contrasts give each pair a hook: firm and yielding, joy and worry, rotting and return.
• Then learn the chain between pairs. The Xugua's "this cannot last, so next comes that" tells you how one pair hands over to the next. Say the steps aloud: birth, immaturity, nourishment, dispute, the army, holding together.
• Use the two halves. The upper canon starts from heaven and earth, the lower from courtship and marriage. Knowing where you are in that story places a hexagram in the right half at once.
• Check yourself against the [list of hexagrams](/iching/hexagrams) rather than a memorised number table; the names and images will stick better than digits.

Reading a cast with the Xugua and Zagua

These texts are background, not verdicts. When you cast a hexagram, the Judgment and any changing lines still carry the answer. But two quick questions drawn from these Wings often sharpen it:

• Where did this situation come from? Read the Xugua sentence that leads into your hexagram. If you cast Pi, Standstill, the Xugua reminds you it follows a time of easy flow, and that it in turn does not last.
• What is its opposite number? Read the Zagua contrast. If you cast Bo, its partner Fu is the return that follows splitting apart; the decline is half of a cycle.

Used this way, the sequence turns a single hexagram into a moment in a longer movement, which is exactly how the Book of Changes asks to be read.