Hexagram 18, Mountain over Wind: Decay (Gu), is the 18th of the 64 hexagrams of the I Ching. It is made of Gen (mountain) above and Xun (wind) below, and it speaks about what to do with problems that have piled up for a long time and how to start fresh.

Hexagram 18 (Gu) at a Glance

Attribute	Detail
Number	18 of 64
Name	Mountain over Wind: Decay (Gu)
Image	☶ over ☴ (mountain over wind)
Inner (lower) trigram	Xun ☴, wind and wood
Outer (upper) trigram	Gen ☶, mountain
Element	Wood (belongs to the Xun house)
Key phrase	Supreme success; it is favorable to cross the great river
Yang lines	3 of 6
Opposite hexagram (every line flipped)	Hexagram 17, Lake over Thunder: Following (Sui)
Inverted hexagram (turned upside down)	Also Hexagram 17, Lake over Thunder: Following (Sui)

The Original Text and Its Meaning

This part gives the classical wording of Hexagram 18 in English, with a plain explanation. If you only care about how the hexagram applies to daily life, feel free to skim it and jump to the later sections.

The Judgment

Decay: supreme success. It is favorable to cross the great river. Three days before the start day, three days after the start day.

In plain words: the old character for Gu shows worms in a vessel, a picture of something left so long that it rots. Yet the text opens with "supreme success", which means very smooth going. Something has been broken for a long time and now someone is willing to repair it, and that is a big opportunity. "Favorable to cross the great river" means being willing to take on hard work and responsibility. The last phrase, "three days before the start day, three days after the start day", reminds you to think for three days before acting and to watch for three days afterward. Repairing what is broken takes careful preparation and a second look.

The Image

At the foot of the mountain there is wind: Decay. In the same way, the noble person stirs up the people and nurtures virtue.

In plain words: wind at the foot of a mountain is the hexagram of Decay. The noble person follows this image by rousing the people and cultivating character. The mountain blocks the wind below it, the air does not move, and over time things grow damp, stale and spoiled. The ancients read this image as a call to wake up people who have settled into old habits and to rebuild the moral root that was forgotten. Fixing what is broken is not only work for the hands. It is also work for people's hearts.

The Six Lines

The six lines of Gu describe six ways of facing a mess inherited from an earlier generation: fixing it early, fixing it gently, fixing it a little too hard, looking away, fixing it and being praised, and choosing to stand outside. Read from the bottom up.

Line	Classical text	Plain meaning
Line 1 (six at the beginning)	Setting right what the father spoiled. There is a son, so the late father is without fault. Danger, but in the end good fortune.	Repairing what a father left damaged, with a child who carries it on, so the elder is spared blame. There is danger, but it ends well
Line 2 (nine in the second place)	Setting right what the mother spoiled. One must not be too rigid.	Repairing what a mother left damaged calls for a gentle touch, not a rigid one
Line 3 (nine in the third place)	Setting right what the father spoiled. A little regret, no great fault.	Repairing the father's damage with some regret, but no great fault
Line 4 (six in the fourth place)	Being lenient with what the father spoiled. Going on brings humiliation.	Going easy on the father's damage; carrying on this way ends in regret
Line 5 (six in the fifth place)	Setting right what the father spoiled. One earns praise.	Repairing the father's damage and being praised for it
Line 6 (nine at the top)	He does not serve kings and lords; he sets higher goals for himself.	Not serving the powerful and keeping to one's own higher purpose

Reading the Six Lines in Everyday Terms

The six lines of Hexagram 18 are a map of six ways people react when they take over something that has been broken for a long time. It might be a family legacy, a company that has gone slack or an old habit inside yourself. Here is each line in everyday language.

Line 1: Fix it early. A person has just realized there is a problem left by the previous generation and starts fixing it right away. It might be an unpaid debt, a strained relationship a parent had with someone, or an old family habit. The line says that when a child fixes things in time, the elder is no longer blamed. There is danger, but in the end good fortune. The key is to act while the damage is still new and has not spread.

If you want to cast a hexagram and see its reading, you can try it on HOROS.

Line 2: Fix it softly, on the mother's side. This line is different from the other five. Problems linked to a mother are often tied to feelings, habits of care and household routines. Fixing them with hard logic and formulas can hurt the person who loves you. The line says not to hold rigidly to one way. It calls for softness, patience and good timing. Some habits take years to change, and that is normal.

Line 3: Fix it a little too hard. A person at this stage means well but works a bit forcefully. They clear out an old workspace and throw away a few valuable things by mistake. They change a process and cause needless friction with longtime colleagues. The line's verdict is a little regret and no great fault. Overdoing it while keeping the spirit of repair is still better than standing by and watching.

Line 4: Go easy on the damage. A person here knows there is a problem but takes the easy route: leave it, let it pass, avoid the trouble. The line gives a sentence worth remembering: going on brings regret. Letting a small problem slide today may turn into a big one in a few years. Keeping the peace in the short term at the cost of long-term trouble is not a wise trade.

Line 5: Fix it and be recognized. This is one of the ruling lines of the hexagram, a high position with a soft nature. The person here has both authority and the right attitude. The repair not only succeeds but earns everyone's praise. No force is needed, and nothing has to be overthrown. It takes the right people, the right principles and the right way of leading. This is the best picture of a reform that has a beginning and an end.

Line 6: Choose to stand outside. The person at the top line no longer wants to be drawn into cleaning up the previous generation's mess. "Does not serve kings and lords" means not taking part in public affairs and not accepting official roles. They keep their own higher purpose, read, cultivate themselves and live like a hermit. This is not running away. It is the choice of someone who has seen enough and knows that some things are not theirs to repair.

What Hexagram 18 May Say About Everyday Life

Love

Casting Decay on a love question often points to a relationship with problems that have built up for a long time and now need attention: things never said, small conflicts put aside, habits that have worn thin. The hexagram does not announce a breakup. It says it is time to tidy up. A single person who casts it may still be carrying an old romance that never fully closed, and it may help to settle it fairly before opening a new chapter. A new love on top of an unhealed wound tends to break open sooner or later.

Career

On career, Decay leans toward a stretch of cleaning up a legacy. You may have just taken a role where the previous person left many problems: a messy process, a tired team, unhappy clients. A company may have reached the point of needing a restructure. Being willing to take on hard work is good, but how you fix things matters even more than being willing. Remember the lesson of the Judgment: think for three days before acting and watch for three days after. Try not to make a big decision in your first week on the job.

Money

On money, Decay suggests this is a time to review, not to expand. Old debts that were never fully paid, investments that lost their appeal but are still held, insurance bought just because everyone did, a lease that is losing money. Sit down and go through all the financial paperwork for yourself and your family. There may be a few things that have gone bad while you still pay for them every month. The I Ching says "supreme success", but it is success for those willing to clean up. Without the cleaning, the success does not come.

Health

On health, Decay is about a long-running pattern more than a sudden event: years of uneven eating, built-up stress, a sadness never dealt with. The picture of wind blocked by a mountain fits well: things inside feel stuck and stagnant. A good place to start is your daily routine. Go to bed at a fixed time, eat regular meals, schedule some movement each day and keep it up for several months. Changing habits from the root tends to work better than a quick fix. If you have felt weighed down emotionally for a long time, talking with someone you trust is also part of the clean-up.

Closing Thought: Broken Is Not the Worst, Ignored Is

If the spirit of this hexagram had to be put in one phrase, it would be this: it opens with a picture of decay and concludes with "supreme success". Few hexagrams in the I Ching dare to put two seemingly opposite things in one sentence. The message is that being broken is not the frightening part, being left alone is. When something is broken and someone is willing to repair it, that is a good time. Fix it early, fix it gently, and fix it through to the end.