The sages observed (images =) incorporeal patterns in order to draw the trigrams and hexagrams. They manipulated the yarrow stalks in order to determine the lines of the trigrams and hexagrams. Thus they enabled the people of later generations throughout the world to be able to resolve suspicions and doubts and to settle cases in which there is hesitation and indecision so that they would not become lost in orienting themselves between the auspicious and inauspicious, repentance and obdurate hate. Their merititorious accomplishment was indeed great.
Now as to the manner in which they produced the trigrams and hexagrams, they went from the root to the trunk, and from the trunk to the branches. [The process they were describing] had a flux of power that seemed to drive it ceaselessly. The active operations of the yarrow stalks were such as to produce divisions and unions, advances and retreats, vertical and horizontal alliances, reflux and compliant flow, and all of these [operations] might proceed anywhere without falling into isolation. How could these [complex operations] be the fabrications of the sages?
The natural operations of the lifebreath and the numerological regularities that became subject to observation in the incorporeal patterns of a lawful sort and then appeared in writing and in diagrams were sufficient to open their minds and find more explicit expression through their hands.
The scholars of recent generations who delight in discoursing on the Yi (i.e., the Yi Jing, Book of Changes) without taking what was just said into consideration, those who pay sole attention to written discourses, not only tear [these realities] apart and produce incoherent [nonsense] that is without any basis, but also what they say pertaining to incorporeal patterns and numerological regularities all force [irrelevant factors] into apparent relationships and hang groundless explanations on seeming connections, and they seem to believe that these [imaginings] have come from the minds and the wisdom of the sages.
In such cases I have vaingloriously taken it upon myself to take them to account for those failings, and for that reason I have joined with my colleagues to assemble the ancient lore in order to write the following four chapters for the sake of the beginning students of these matters so that they will not [later] find reason for doubt or confusion.
Written by my own hand in [the spring of 1184], the true hermit of Yun Tai.
[During this period, Zhu Xi was administrator of the Yun Tai daoist monastery in Shan-xi.]
First, note the importance given to ¶H xiang`. Literally this word means "elephant," and (probably due to the use of ivory to produce carved figurines) its second meaning is "image." But the images Zhu Xi refers to are entities between the visible world and the noumenal world. They are regularities of nature that can only be indirectly observed. A commonplace example would be the paths of the planets across the backdrop of the fixed stars. The pathway is complex but invariable, invisible but absolutely determinative.
Even using the worldview of the scientific West in the twenty-first century, we might ask, "Which comes first, the regularities of nature that make specific protons, neutrons, electrons, etc., possible? Or do the so-called elementary particles come first? Was there some order-giving entity or condition that appeared immediately following the Big Bang to be followed by elementary particles later? If not, why is it that everything we can learn suggests that matter as far distant from us in space and time as we can see is the same as the matter we experience in our own back yards?
The basic and unstated idea of the Book of Changes seems to be that by manipulating fifty stalks of yarrow (milfoil), the entire history of the universe can be recapitulated right down to the current problematic situation on which guidance is sought. In performing the several manipulations involved in casting a hexagram, one first takes a reading on the level of cosmic Yin and Yang, and following this one recapitulates things on the level of the four cosmic images (¥|¶H, si xiang). In the above passage Zhu Xi does not yet trace things through all six levels depicted in the six lines of a hexagram.
Rather than goes from Yin and Yang to the Four Images and from there to the Eight Trigrams, and so on, at this point Zhu Xi contents himself with a more figurative expression of the relationships among the constituent levels of reality. He compares the casting of a trigram, and the structure of the fundamental levels of reality, to the biological structure of a tree. First, below the ground where we cannot see it, there is the root. Then above that there is a trunk (or perhaps he would allow that there are two trunks stemming from one main root), and from the trunk there grow branches. In the terms of this analogy, the root is the Tai-ji (¤Ó·¥, Great Ultimate, the ground state of the Universe that comes before the Big Bang as it were), the trunk is cosmic Yin and Yang, and the major branches are the Four Images. Without saying any more Zhu Xi causes us to imagine smaller branches, twigs, and leaves -- in other words a vast ramiform structure growing out of a cosmic singularity. And he asserts that this "tree" is a vibrant, growing entity.
Zhu Xi has himself asserted, elsewhere, that the Yi Jing is a book formed of several historical strata, and that the fundamental stratum was a book of divination. That is not to say that it was a book of fortune telling, but that it was a guide that could indicate the predominant forces operating in a situation at the time a hexagram was cast. It was intended to resolve uncertainty -- uncertainty about what to do. The implicit understanding seems to have been that if one truly understands the forces at work in some situation one is better able to do something on one's own to change that balance of forces to a more favorable one should one so desire.
So it is significant that in this introductory chapter Zhu Xi explicitly cautions against looking solely at passages plucked from the book and using them to support one's own ideas, and advocates understanding the reality that the book attempts to describe. So in this book he is clearly talking primarily about the structure of reality, and not merely about the rules of divination in a book of some antiquinarian interest (the supposed "fabrications of the sages" as he calls it).