The I Ching, or Book of Changes, is an ancient Chinese system of guidance, also used in Korea. Coins are thrown to determine 6 lines which make up one of 64 possible hexagrams (picture). The meanings of the hexagrams are described in many books called commentaries, from the first written by King Wen in the 12th century B.C., to Confucius in the 6th century B.C., to ones written in modern times.

The central idea of the I Ching comes from Taoism: the balance of the opposite forces of yin and yang. Yin energy is yielding, dark, and feminine. Yang energy is firm, light, and masculine. Many other opposites - north/south, night/day, earth/heaven - are also represented by yin/yang.

For a reading, a person thinks about a particular situation and asks a question about it. Then three coins are thrown. The tail side of each coin is yin, counted as 2 points. The heads side is yang, counted as 3 points. On each throw, the coin values combine to make 6, 7, 8 or 9. 6 and 8 are yin, written as a broken line. 7 and 9 are yang, written as a solid line. The coins are thrown 6 times to generate six broken or solid lines, making up the hexagram.

Each hexagram has a name, such as the Creative, Difficulty at the Beginning, Standstill, Deliverance (from the Richard Wilhelm translation). The commentaries provide interpretations of the meanings of each hexagram. The person doing the reading can get a sense of how things stand now, and what should be done next to make sure that things turn out well.