Six-line divination, also known as the "Najia method," is one of the most precise and systematized branches of ancient Chinese divination. To understand it, we must first examine it within the broader framework of the study of the Book of Changes.
The Book of Changes was originally a book of divination, as explicitly recorded in the "Spring Official" section of the Rites of Zhou: "The Grand Diviner oversees the methods of the Three Changes: first, Lianshan; second, Guicang; third, Zhouyi. Each has eight primary trigrams and sixty-four derived hexagrams." Here, "primary trigrams" refers to the eight trigrams, and "derived hexagrams" refers to the sixty-four hexagrams. Six-line divination is based on these sixty-four hexagrams. Through specific methods of casting a hexagram, it incorporates time, space, and human affairs into the hexagram images for systematic deduction and analysis.
However, six-line divination was not the method used in the Zhou dynasty. Traditional Zhouyi divination formed hexagrams by manipulating yarrow stalks, following the process of "four operations make a change, and eighteen changes make a hexagram" (Commentary on the Appended Phrases, Part One). Though this method was solemn and sacred, it was cumbersome to perform, and the interpretations of the hexagram and line statements allowed considerable leeway, with no uniform standard for judgment.
The emergence of the six-line Najia method was a major turning point in the history of the study of the Book of Changes. It incorporated the Heavenly Stems and Earthly Branches into the hexagram
