Trigrams and Component Lines
“卦”是由“—”和“- -”排列组合而成的一套符号系统，其中的“—”为“阳爻”，“- -”为“阴爻”。每三“爻”合成一卦，可得“八卦”。每六“爻”合成一卦，可得“六十四卦”。“卦爻”的产生与占筮有关。古人通过分取蓍草，演算其变化之数，从而确定卦爻，以预测吉凶。后人为卦爻赋予各种象征意义，并用以理解和阐发包括人事在内的天地万物的运行变化及其法则。
A gua (trigram) is a system of symbols consisting of undivided lines (—) and divided lines (- -). The undivided line (—) is a yang line while the divided one (- -) a yin line. Three lines make a trigram, and there are eight such trigrams. When six lines are put together, they together make 64 hexagram combinations. Trigrams and component lines were created partly for the purpose of divination. Ancient Chinese people used yarrow stalks to make hexagrams, calculated the variations they suggested, and consulted them for the purpose of divination. Later on, people used trigrams symbolically to explain the changes and the laws regulating the changes that occurred in people and everything else, and why and how these changes took place.
When the eight trigrams were invented, they embodied the images of all things. When the eight trigrams were multiplied by eight trigrams and permuted into the 64 hexagrams, all the 384 lines were included. (The Book of Changes)
When sages saw the changes or events happening under heaven, they observed the similarities of the events and responded with appropriate rites and rituals. They judged their implications of the changes by obtaining explanations from the yao. (The Book of Changes)