Module 2
Meeting the line (yao)
Goal of this module
Move from the concept of yin and yang to the basic symbol of the Zhou Yi, and understand why a line can change.
What a line is
The previous module dealt with yin and yang as a concept. To write it down, stack it and compute with it, you need a symbol. That symbol is the line — in Chinese, 爻 (yáo).
One line records one yin-yang judgment. That is all it does. It records no degree, no good or bad, no time.
Two ways to draw it
Yin line
Two segments with a gap between them. Yielding, empty, receiving, hidden.
Traditional name: six
Click it and it turns into a yang line.
Why a line can change
Because yin and yang themselves turn into each other (module 1). A symbol that stands for yin and yang has to be able to show that turn.
The rule for how a line changes is one sentence long: a yang line becomes a yin line, a yin line becomes a yang line. Nothing else is possible, because there are only two states.
But keep two things apart. Whether a line changes depends on the number you get when casting, which is module 8. What it changes into is fixed for good. The first has conditions; the second has none.
One line still says nothing
This is the point most often skipped here, and the one that costs the most later.
A line is a word, not a sentence. To carry meaning it needs at least three lines to make a trigram (module 3) and six to make a hexagram (module 6), and then the question of which position it holds (module 7).
So calling a yin line “bad” on sight is like seeing the word “not” and concluding the whole sentence is a denial. Learn the symbols first; meaning comes after.
Exercises
1What does one unbroken stroke ——— stand for?
Right. Whole and unbroken, matching solid, firm and manifest: that is the yang line. Traditionally it is called “nine”.
That step went astray. A yin line is two segments with a gap between them. One way to hold onto it: whole is yang, broken is yin — yang is full, yin is empty.
2When a yang line changes, what does it become?
Right. A line has only two states, so a change has only one destination: yang to yin, yin to yang. There is no third possibility.
That step went astray. Lines do not disappear. A hexagram always has six of them; a change alters the yin or yang of one line and never the count. This matters a great deal once you reach resulting hexagrams.
That step went astray. Position affects what the line means, but not what it becomes. Yang becomes yin, and that holds in any position.
This is the entire mechanism behind “moving line → resulting hexagram” later on. It looks trivial, but it is the whole of it.
3From a single yin line, can you tell whether things turn out well or badly?
Right. Right. A line records one yin-yang judgment and carries no fortune with it. Fortune comes from the position the line holds, the hexagram it belongs to, and its relationships with the other lines — the subject of later modules.
That step went astray. This is module 1’s error in a new costume: taking yin for bad. A yin line only says “this place is yielding, receiving, hidden”. It carries no evaluation of its own.
Common mistakes
These are not filler. They are the specific places beginners go wrong.
Reading the gap in a yin line as “broken, therefore bad”.
The gap is only a mark, there to tell it apart from the unbroken yang line. What it stands for is yielding, empty, receiving — not damaged. This is module 1’s value judgment showing up again.
Thinking one line by itself can tell good fortune from bad.
A line records a single yin-yang state. Fortune depends on which position it holds, which hexagram it belongs to, and how it answers the other lines. Drawing a conclusion from one line in isolation is the most common fault in reading a casting.
Thinking a line changes at random, with no rule.
Which line changes is decided by the number you get when casting: 6 and 9 change, 7 and 8 do not. How it changes is entirely fixed: yang becomes yin, yin becomes yang. Both ends are governed by rules, and nothing in between is arbitrary.
Drawing a yin line with unequal halves, or with no gap in the middle.
A yin line is two segments of equal length with a clear gap between them. Drawn vaguely it blurs into a yang line — and with six lines stacked, one vague line means the whole hexagram is misread.
You have it when
You can tell yin from yang at a glance, say what a line becomes when it changes, and explain why a single line on its own is not a verdict.
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The prose, examples and exercises on this page are written for this site (L4). Passages quoted from the Zhou Yi and the Ten Wings are L1/L2 and in the public domain; per-passage sourcing is given on the hexagram pages.