Correct place and central lines in the I Ching: why lines 2 and 5 are favoured

Every line of a hexagram is read twice: once for what it is (yin or yang) and once for where it stands (positions 1 to 6, counted from the bottom). When the two fit, the line is in its correct place (當位 or 得位); when a line sits in the second or fifth position, the middle of its trigram, it is central (中). These two ideas explain a surprising number of verdicts in the line texts, including why lines 2 and 5 are so often favourable and why a line in the wrong place so often comes with a warning.

Correct place: odd for yang, even for yin

The rule is simple. Positions 1, 3 and 5 are odd numbers and count as yang places; positions 2, 4 and 6 are even and count as yin places. A solid (yang) line in an odd place, or a broken (yin) line in an even place, is "correct"; the reverse is "not correct" (不當位, 位不當).

You can see the two extremes in the last pair of the book. In Ji Ji, After Completion, all six lines are correct: yang, yin, yang, yin, yang, yin. The Tuan commentary says so directly: 剛柔正而位當也, "firm and yielding are upright and their places fitting." In Wei Ji, Before Completion, every line is in the wrong place, and the Tuan says 雖不當位，剛柔應也, "although none is in its proper place, firm and yielding correspond." The tradition does not treat Ji Ji as simply good and Wei Ji as simply bad: a perfectly ordered situation has nowhere left to go, while a disordered one whose parts still answer each other can still be completed. Correct place is one factor, never the whole verdict.

Not everyone applied the rule to every line. Wang Bi, in his Outline of the Zhouyi (周易略例), argued that the first and top positions mark the beginning and end of a matter and have no fixed yin or yang place; for him correctness mattered chiefly in positions 2 to 5. Most later readers still mention it for all six, but it is worth knowing the tradition was not unanimous.

Centrality: the middle of each trigram

A hexagram is two trigrams stacked. Line 2 is the middle of the lower trigram, line 5 the middle of the upper. A central line stands for balance: not hasty like the first line, not overreaching like the third, not exposed like the top. The Great Commentary (Xici) sums up the pattern of the positions in a famous passage:

• 二多譽，四多懼 — "the second has much praise, the fourth much fear," because the fourth is close to the ruler in the fifth place.
• 三多凶，五多功 — "the third has much misfortune, the fifth much achievement," a difference of rank.

Those two sentences are a fair summary of how the line texts actually fall out. Line 2 is the official in the field, trusted and at a respectful distance; line 5 is the ruler's seat; line 3 sits at the unstable top of the lower trigram, and line 4 at the anxious threshold of the upper.

中正: central and correct

When a line is both central and correct, a yin line in the second place or a yang line in the fifth, the commentaries call it 中正, central and upright. This is the strongest position a line can have.

• In Qian, the fifth line is the flying dragon in the heavens: yang in a yang place, at the centre of the upper trigram.
• In Kun, the second line, "straight, square, great; without practice nothing is unfavourable," is yin in a yin place at the centre of the lower trigram.
• In Song, Conflict, a hexagram full of warnings, the fifth line simply reads 訟，元吉, "contention: supreme good fortune," and its small Image explains 以中正也, "because it is central and upright." The impartial judge settles the dispute.

When centrality outweighs correctness

A yin line in the fifth place is central but not correct, and yet the tradition often treats it warmly. The fifth line of Kun, "a yellow lower garment: supreme good fortune," is yin in a yang place; its small Image puts the good fortune down to 文在中也, "refinement within, at the centre." Many hexagrams whose ruler is a yin fifth line, such as Da You, are among the most favourable in the book. Cheng Yi made the principle explicit: centrality weighs more than correctness, because what is central is never far from right, whereas a correct line can still be one-sided.

The opposite case teaches the same lesson. The third line of Qian is yang in a yang place, perfectly correct, but not central: "all day long the noble one is active and alert, in the evening still wary: danger, no blame." Correctness does not rescue the restless third position.

When the wrong place explains a warning

Where the small Images (小象) explain a bad verdict, 位不當也, "the place is not fitting," is one of their stock reasons, and it is very often a yin line in the third place: a soft line in a position that demands firmness.

• The third line of Lü, Treading: "a one-eyed man who can see, a lame man who can walk; he treads on the tiger's tail and it bites: misfortune." The small Image: 咥人之凶，位不當也. The line overrates itself; it is weak in a place that needs strength.
• The third line of Yu, Enthusiasm: "looking upward for enthusiasm brings remorse." Again the Image says the place is not fitting. The line waits on others' approval instead of acting from its own position.

In both, the position gives you the reason behind the warning, and the reason tells you what to change: stop pretending to strength you do not have, or stop leaning on someone else's mood.

How to use this when you read a cast

You do not need to compute anything before reading the text; the line texts already embody these judgements. But when a line moves in your cast, a quick check of its position helps you understand why it says what it says:

• Note the place. Is the moving line in position 2 or 5? Central lines usually counsel staying with a balanced course you are already on.
• Note the fit. Is it yin in an odd place or yang in an even place? If the text warns you, ask where you are acting out of character for the role you hold.
• Weigh third and fourth lines carefully. Their warnings are often about transition: leaving one level, approaching another.
• Do not overrule the text. Position explains a verdict; it never cancels one. If the line says good fortune, an "incorrect" place does not turn it into bad fortune.

For the relations between lines, which work alongside position, see correspondence and holding together; for which line governs the whole hexagram, see the ruler of the hexagram. Then cast a reading and look at your moving line with these questions in mind.