Preface to the Zhouyi

The Changes as a book -- in the meanings of its hexagrams, lines, and images, the dispositions of Heaven, Earth, and the myriad things are revealed. What the sages did for the world and for posterity reaches its highest expression here. Before things come into being, it opens up their natures; after things have taken form, it completes their transformations. Therefore it exhausts numbers to fix the images of the world and determines the auspicious and inauspicious for all under Heaven. The sixty-four hexagrams and three hundred eighty-four lines serve to follow the principles of human nature and destiny and to exhaust the Way of change and transformation. Dispersed into principles, there are ten thousand distinctions; unified in the Way, there is only one ultimate ground. This is why the Changes has the Supreme Ultimate, which gives birth to the Two Modes. The Supreme Ultimate is the Way; the Two Modes are yin and yang.

Yin and yang together are one Way. The Supreme Ultimate is the Limitless. All things in their birth carry yin on their backs and embrace yang -- there is none that does not possess the Supreme Ultimate, none that does not possess the Two Modes. Through their dense intermingling and mutual response, transformation is endless, and every form possesses the impulse of life. When spirit issues forth its intelligence, when feeling emerges, it becomes the myriad threads of existence. This is why the Changes determines the auspicious and inauspicious and gives rise to great undertakings. The Changes is the Way of yin and yang. The hexagrams are the substance of yin and yang. The lines are the movements of yin and yang. Though the hexagrams differ, what they share is odd and even; though the lines differ, what they share is the six positions. Thus the sixty-four hexagrams form its body, and the three hundred eighty-four lines serve as its function. Remotely it extends beyond the six directions; close at hand it lies within one's own body. In every moment, in every movement and stillness, there is none that does not contain the image of a hexagram, none that does not hold the meaning of a line. The Way of the Changes is supremely great, encompassing all, and its function is supremely numinous, preserving all.

Time has never been fixed in one state, and hexagrams have never had fixed images. Events have never been exhaustible, and lines have never had fixed positions. To illuminate lines by a single event and then be unable to extend it further -- that is not the Changes. To know only what is called the meaning of hexagrams, lines, and images but not to know their function -- that too is not the Changes. Therefore one who grasps it through the operation of spirit and the movement of the mind, whose virtue accords with Heaven and Earth in determining fortune and misfortune, accords with the sun and moon in brightness, accords with the four seasons in sequence, and accords with spirits and ghosts in predicting fortune and misfortune -- only then can one be said to know the Changes. Even so, what the Changes presents in its hexagrams is what has already become visible. What has already taken form and become visible can be known through words. But what has not yet taken form or become visible cannot be sought through names. Then what is the thing we call the Changes, truly? This is what students must understand. By Cheng Yi of Henan.