The Tuan, or Commentary on the Judgment (彖傳, tuàn zhuàn), is one of the ancient commentaries that make up the Ten Wings. It takes the judgment of each hexagram and explains why it says what it says. It fills two of the ten wings: one for hexagrams 1 to 30 and one for 31 to 64.
What it does
The ancient judgment is short and often cryptic. The Tuan takes it apart with tools the original text never names:
- The two trigram figures and their qualities: strength, stillness, danger, joy.
- The line positions: which line is central, which is correct, which one rules.
- The language of yin and yang, of firm and yielding.
For example, the Tuan of Activity opens with 大哉乾元，萬物資始: "great is the origin of the creative; from it all things take their start." From the bare 元亨利貞 it builds a view of the whole cosmos.
In your reading
It isn't part of the text you consult, but it helps a lot when a judgment feels obscure. It often gives you the key to why a hexagram is favorable or hard. It's also the source of many ideas now taken as part of the system, such as the ruling line.
Origins: tradition and scholarship
Tradition credits the Ten Wings to Confucius. Scholars think the Tuan was written later, probably in the Warring States period, and it's among the earliest of the commentaries. The word tuàn itself is obscure; it's usually taken to mean "to decide" or "to judge."