Two solid lines under a broken one. Dui is the trigram of the lake: pleasure, speech and openness at the surface. It describes what is enjoyable in a situation, and its opening is at the top.
The judgement belongs to Hexagram 58, The Joyous, and it is short. Legge's 1882 English gives progress and attainment, with the qualification that it will be advantageous to be firm and correct.
That qualification does real work. Of the eight doubled trigrams this is the one most likely to be read as plain good fortune, and its own judgement attaches a condition to it immediately. Pleasure in this book is not treated as suspect, which is unusual for a text of its period, but it is treated as something that goes wrong when there is nothing firm underneath it. The trigram has two solid lines below for exactly that reason.
The Image is two lakes joined, one resting on the other, and from it the noble person meets with friends for conversation and for practice together.
This is the most sociable Image in the book and the least solitary piece of advice in it. Where most Images tell the noble person to cultivate something privately, this one says go and talk to people, and do the work alongside them. The natural picture supports it: connected lakes replenish each other, and a lake on its own evaporates. What the text does not say, and readers supply, is that the conversation is pleasant. It says the conversation happens, and that practice accompanies it. Those are two separate requirements.
Dui is two solid lines with a broken one on top. The Shuo Gua gives it the lake or marsh, the youngest daughter, the sheep, the mouth and the tongue, the direction west, the sorceress, and the quality yue, pleasure or delight. It also gives it breaking apart, which sits strangely in that list until you look at the top line, which is open.
The mouth is the attribute that carries the trigram. Dui is speech as much as pleasure: talking, persuading, entertaining, the exchange that makes company worth having. As the lower trigram it means the enjoyment or the talking is at the base of the situation. As the upper trigram it means it is at the surface, which is where a lake is in any case.
What Dui does not describe is depth, and the figure is candid about it. Two firm lines below, one broken above: the substance is underneath and the opening is on top. Its opposite line for line is Gen, which is closed at the top exactly where Dui is open. Asked what is happening, Dui says there is real pleasure here, or real communication. Asked whether the pleasure is well founded, it points down at the two lines below it and at whatever trigram is supporting them. It is a narrow answer, and it is the one the figure can actually give.
Enjoyment and talk. Dui is the part of a relationship that is genuinely good company: laughing, conversation, attraction, the ease of being around somebody. The book does not treat any of that as trivial, and a reading should not either.
The trigram's caution is structural rather than moral. The open line is at the top, so what is exposed is the surface, and Dui says nothing about what lies under it. In a relationship question this most often marks something that works well at the level of company and has not yet been tested anywhere else. That is an accurate description of many good relationships early on. It becomes a problem only when a reading treats the pleasure as evidence about the depth.
Work that runs on communication and morale: negotiation, teaching, client work, anything where the quality of the talking is the quality of the job. Dui below means the enjoyment or the persuasion sits in the querent's own work. Dui above means it is what surrounds them, a pleasant environment or a group that talks well.
The trigram's practical value is that it identifies where the goodwill in a situation actually is. Its risk is the one drawn in the figure, an open line on top. Work that is enjoyable and unsupported stays pleasant right up until something is asked of it, and the trigram will not tell you whether the support is there.
Money spent on pleasure, money made through people, or a financial situation that is comfortable at the surface. Dui is a sociable trigram and in money questions it usually involves other people: shared costs, generosity, an arrangement that exists because everybody gets on.
Its caution is that open line at the top. Comfortable is not the same as sound, and pleasant arrangements between people who like each other are the ones least likely to have been written down anywhere. The useful move is to find out whether the informal thing is documented. Nothing here is advice about any particular spending or decision.
Have the conversation, and have it with somebody who will enjoy it. This trigram's method is exchange rather than solitary effort, and its Image is unusual in the book for saying so outright. Then check the two lines underneath: before committing to anything on the strength of how good the discussion felt, confirm that the practical part is real. Both halves of that instruction are in the figure, and the second half is the one people skip.
Dui is 110: two yang lines with a single yin on top. The open line is at the surface, which is what a lake is, and everything the trigram means comes from that.
Turn the figure over and the yin line drops to the bottom. That is Xun, the Wind Trigram, where the opening is underneath and the trigram gets in rather than invites. Dui and Xun are one of only two inversion pairs among the eight trigrams. Dui's opposite, line for line, is Gen.
The single yin line shows most clearly against solid ones. Dui above Qian gives Hexagram 43, Breakthrough: five yang lines with one yin at the very top, which the text reads as something that has to be removed, and it is unusually explicit about the danger of doing that carelessly. Reverse the order, Dui below and Qian above, and you have Hexagram 10, Treading, where the pleasant, talkative trigram sits underneath something considerably harder than itself. Same components, opposite order, and one becomes a confrontation while the other becomes a question of tact.
Doubled, the pleasure is stated twice and the hexagram has to say what joy is for. The trigram alone only reports that it is present.
In the Zhou-era layer, roughly ninth to eighth century BCE, the material is concrete and social: marshes, gatherings, offerings, speech. The abstraction into a trigram of joy came later.
The Ten Wings, compiled across the Warring States and Han periods, do the abstracting. The Shuo Gua gives Dui the youngest daughter, the sheep, the mouth, the direction west, and, notably, the sorceress or shamaness. That last attribute is quietly interesting: it is one of the few places in the commentary where a specifically religious professional is attached to a trigram, and most modern English summaries drop it without saying that they have.
The word behind the trigram, yue, is written with a character closely related to the one for speech, and Chinese commentators have argued for a very long time about whether the primary sense is speaking or delighting. Legge in 1882 took pleasure. Wilhelm in 1924 gave The Joyous, which is the name English readers know. Both are defensible, and both quietly close down a question the Chinese leaves open, which is the general problem with reading this book in translation at all.
One structural accident of the King Wen sequence is worth knowing. The doubled Dui sits at fifty-eight, immediately after the doubled Xun at fifty-seven, so the two trigrams that invert into each other also sit next to each other as hexagrams. Whether the editors intended it or whether it fell out of the pairing rules is not something the sequence explains, and commentaries that claim to know are reasoning backwards from the result.
The first misreading is treating Dui as a straightforwardly good result. It is the most cheerful-looking trigram in the set and readers hand it out as a yes. Its own judgement attaches a condition immediately, and the figure puts the opening at the top. Pleasure is being reported here, not endorsed.
The second is the opposite, and it is the older prejudice. A long tradition of commentary treats joy as morally suspect and reads Dui as frivolity, superficiality or seduction, an attitude the sorceress attribute encouraged. That is a reading imported from centuries of moralising rather than taken from the figure, and the book itself is markedly more relaxed about pleasure than its commentators are.
The third is missing the mouth. Dui is speech as much as delight, and a great many readings that go looking for enjoyment are in fact being told something about what is being said, by whom, and to whom. In a question about a disagreement, a negotiation, or a person who talks well, that is the more useful half of the trigram, and it is the half most English summaries barely mention, if they mention it at all.
Put a real question to the coins.