What the book is
The I Ching, the Book of Changes, is a Chinese text whose core dates to roughly 1000 BCE, in the early Western Zhou period, drawing on divination practice older than the writing itself. It is not a story and not a set of instructions. It is a system of sixty-four figures, each built from six lines, with short texts attached to each one.
The figures are the substance. Each names a configuration: a way circumstances can be arranged, and the pressures that arrangement carries. The sixty-four together are meant to be exhaustive, a complete set of the shapes a situation can take. Consulting it means arriving at one of those figures by a procedure that nobody controls, then reading what the system says about that configuration.
Everything below is how that machinery works. None of it requires believing anything in particular about why it should mean something.
The figure: six lines
Every hexagram is six horizontal lines stacked one above another. Each line is one of two kinds: solid, called yang, or broken, called yin. Six positions with two possibilities each gives sixty-four combinations, which is exactly the number of figures in the book. The set is closed; there is no sixty-fifth.
A hexagram, six lines, read from the bottom upward. The lowest line is line one; the top line is line six.
Numbering runs upward because that is the order casting produces: the first throw makes the bottom line, the sixth throw makes the top. The figure is read the same way, from the ground up, and the position of a line is part of what it means. A solid line low in the figure and the same solid line high in it are not read as the same thing.
The eight trigrams
Between the single line and the six-line figure there is a middle unit: the trigram, three lines stacked. Three positions with two possibilities gives eight, and those eight are the vocabulary the sixty-four are written in. Each carries a name and an image drawn from the natural world.
Read each of those figures from the bottom up as well. Heaven is three solid lines, Earth three broken. The other six are the mixtures, and the position of the odd line out is what distinguishes them: Water is a solid line held between two broken ones, Fire the reverse.
A hexagram is two trigrams stacked. Lines one to three form the lower trigram, four to six the upper. Eight possibilities in each position, stacked, gives the same sixty-four. So a figure can be read two ways at once: as six lines in sequence, and as two natural images in relation, one sitting above the other.
Casting with three coins
To arrive at a figure you need a procedure that produces one line at a time, six times, with no one choosing. The common modern method uses three coins.
Throw all three. One face counts 3, the other counts 2. Add them. Three coins at two or three each can only total 6, 7, 8, or 9, and each total means a specific kind of line.
| Total | Line | Drawn | Odds |
|---|---|---|---|
| 6 | Old yin | Broken, moving | 1 in 8 |
| 7 | Young yang | Solid, holds | 3 in 8 |
| 8 | Young yin | Broken, holds | 3 in 8 |
| 9 | Old yang | Solid, moving | 1 in 8 |
The odds fall straight out of the coins. There is exactly one way to throw three twos and make a 6, and one way to throw three threes and make a 9, but three different ways to land a 7 and three to land an 8. That is why the extremes are the rare results.
Repeat six times, recording each line from the bottom up, and you have a hexagram.
The yarrow stalks, and why the odds differ
The older procedure uses fifty dried yarrow stalks. One is set aside and the rest are divided, counted off in fours, and set aside again through three rounds of manipulation for each line, six lines to a figure. It is slow: a full consultation takes the better part of an hour, and the slowness is part of the practice.
The arithmetic of the counting is not the interesting part. The consequence is. The yarrow procedure does not produce the four results in the same proportions the coins do.
| Result | Line | Yarrow | Coins |
|---|---|---|---|
| 6 | Old yin | 1 in 16 | 2 in 16 |
| 7 | Young yang | 5 in 16 | 6 in 16 |
| 8 | Young yin | 7 in 16 | 6 in 16 |
| 9 | Old yang | 3 in 16 | 2 in 16 |
Two things are worth noticing. First, under the coins a changing yin and a changing yang are equally likely; under the yarrow a changing yang is three times as likely as a changing yin. The two methods disagree about which kind of line tends to be the one in motion.
Second, and less obvious: the total chance that any given line moves at all is the same under both methods, one in four. Yarrow moves 1 in 16 plus 3 in 16; coins move 2 in 16 plus 2 in 16. Both come to 4 in 16. So the two methods produce moving lines at the same rate and disagree only about their character.
This site casts with the three-coin method, and says so on every reading.
Moving lines and the second figure
A line thrown at the far end of its kind, a 6 or a 9, is a moving line. It is not simply solid or broken. It is read as already turning into its opposite: an old yin becoming solid, an old yang becoming broken.
That is why a cast can yield two figures instead of one. Take the hexagram as it landed. Then flip every moving line to its opposite and read off the figure that results. The first is the primary hexagram, the second is the relating hexagram, and the pair together describes a configuration under tension rather than a settled one.
If no line comes up 6 or 9, there is no second figure, and the reading is of one hexagram only. Given a one-in-four chance per line, a cast with no moving lines at all happens about eighteen times in a hundred.
The Judgment and the Image
Each of the sixty-four figures carries two short attached texts, and they are different kinds of statement rather than two halves of the same one.
The first, usually called the Judgment, speaks about the configuration directly. It characterises the situation the figure names and often states what sort of conduct the configuration favours.
The second, the Image, is built from the structure. It names the two trigrams as the natural phenomena they stand for, sets them in the relation the stacking puts them in, and draws a line of conduct out of that picture. The Image is where the trigram vocabulary earns its place: to read one you have to know which two images are stacked and in what order.
This site shows both texts on a reading, in the Wilhelm-Baynes translation, with attribution. What matters for understanding the system is knowing that they are answering two different questions about the same figure.
Forming a question
The system is built to describe configurations, so questions shaped like configurations have somewhere to land. Open questions do this: what is actually going on here, what am I not accounting for, what does this situation ask of someone in it.
Closed questions fit the machinery poorly. A figure is not a yes or a no, and nothing in the sixty-four is structured to answer whether a specific event will occur on a specific date. Asking that way tends to produce a reading you then have to argue with.
You do not need a question at all. Casting without one gives a figure to read as a general description, which is a reasonable way to learn what the sixty-four are like.
Whatever you ask, write it down before you cast, or at least fix it in your head. A question that drifts while you read is a question the reading cannot be checked against.
Reading further
The fastest way to get a feel for the sixty-four is to cast and read, several times, paying attention to the structure rather than only the text. Cast a reading, and turn on the option to watch each throw: the coins, the totals, and the lines they make are all shown as they land.