Water

Water is the most philosophically loaded image in the Book of Changes. It flows downward, fills every hollow before moving on, takes any shape, avoids no dangerous place, and never loses its nature. Its home hexagram is 29 K'an - The Abysmal (Water), where it teaches the right conduct in danger:

The Abysmal repeated.
If you are sincere, you have success in your heart,
And whatever you do succeeds.

The commentary there gives the classic portrait: "It flows on and on, and merely fills up all the places through which it flows; it does not shrink from any dangerous spot nor from any plunge, and nothing can make it lose its own essential nature. It remains true to itself under all conditions." The same hexagram makes water the model of steady character: "Water reaches its goal by flowing continually. It fills up every depression before it flows on."

This patient filling of hollows recurs wherever the book counsels thoroughness over haste. In 04 Mêng - Youthful Folly the spring rising at the foot of the mountain "does not know at first where it will go. But its steady flow fills up the deep place blocking its progress, and success is attained." In 08 Pi - Holding Together (union) the same movement becomes the model of society: "Water fills up all the empty places on the earth and clings fast to it." And in 15 Ch'ien - Modesty water is the agent of heaven's leveling law: "High mountains are worn down by the waters, and the valleys are filled up."

Yet water is also danger itself: the abyss, the pit, the deep ravine. K'an means a plunging in, and its hexagram warns that in the abyss "one falls into a pit." The oracle's ideal is the man who, like water in a ravine, escapes because he behaves correctly, striving "to attain small things only" and rising no "higher than the lowest point of the rim." The image runs on through Obstruction (39), Oppression (47), and the wells and limitations of hexagrams 48 and 60.

This is the master image the I Ching shares with the Tao Te Ching. Chapter 8 calls the highest good like water, which benefits all things and dwells in the low places men disdain; chapter 78 observes that nothing is softer than water, yet nothing surpasses it in wearing down the hard.