《易传·系辞传下·第一章》
八卦之中，乾坤相对，震与巽相对，离与坎相对，兑与艮相对，八卦对待成列，举凡天地间两两相重，成为六位的卦，以应事实的需要，因而八八六十四卦、三百八十四爻，都在其中了。阴阳两爻，递相推移，宇宙间的千变万化，都在其中了。各卦各爻，圣人都系以文辞，分别指出吉凶的征兆，于是人间所有的动作营为，和趋吉避凶的道理，都在其中了。
八卦成列，像在其中矣；因而重之，爻在其中矣；刚柔相推，变在其中焉；系辞焉而命之，动在其中矣。
Among the eight trigrams, Qian and Kun are opposites, Zhen and Xun are opposites, Li and Kan are opposites, and Dui and Gen are opposites. Eight trigrams stand in pairs to form hexagrams, and all the possible pairs that occur in heaven and earth become six hexagrams, satisfying the needs of reality. Thus, there are sixty-four hexagrams and three hundred eighty-four lines in total. With the mutual transformation of the two lines of yin and yang, all the myriad changes of the universe are contained therein. The sages have attached texts to the various hexagrams and lines, indicating the signs of auspiciousness and inauspiciousness. Therefore, all human actions and principles for seeking good fortune and avoiding disaster are contained therein.