Gu in the Sequence of Hexagrams: 'One who follows others with joy will surely encounter affairs; hence Following is succeeded by Gu.' Following the meanings of the two hexagrams establishes their order.
For one who follows others with delight will inevitably have affairs; without affairs, what delight or following could there be? This is why Gu succeeds Following. Gu means affairs. Gu does not mean affairs by literal gloss, but rather that affairs arise.
As a hexagram, it has wind beneath the mountain. When wind is beneath a mountain and encounters it, it whirls back, throwing things into confusion; this is the image of Gu. The meaning of Gu is decay and ruin.
In writing, it consists of worms over a vessel; worms inside a vessel signify decay. The Zuo Zhuan states: 'Wind brings down the mountain; a woman deludes a man.' An elder daughter placing herself beneath a younger son confuses his affections.
When wind meets a mountain and whirls back, things are disturbed and thrown into disorder; this is the image of having affairs to manage, hence it is said that Gu means affairs. Managing affairs after they have decayed is also an affair.
Speaking from the hexagram's image, it shows how Gu is formed; speaking from the hexagram's talent, it shows how Gu is remedied. Once there is decay, there is the principle of restoring order.
Since ancient times, order has always arisen from chaos; when chaos occurs, the way to order opens, which is the natural course. If one uses the talent of the hexagram to remedy Gu, one can achieve supreme success.
The greatest aspect of Gu is rescuing the world from hardship and perilous obstacles; hence it is said, 'It is advantageous to cross the great river.' Jia is the first of numbers and the beginning of affairs.
Just as in the heavenly stems Jia and Yi, or terms like 'first rank' and 'primary ordinance,' all denote the head. It is the genesis of affairs.
The way of remedying Gu requires thinking about the three days before and after it; tracing the origins before and after is the Dao of remedying abuses so that order may endure.
'Three days before Jia' means investigating the causes prior to this; 'three days after Jia' means anticipating what will happen subsequent to this. Mentioning one day, two days, up to three days expresses deep deliberation and far-reaching anticipation.
By investigating the causes, one knows the way to remedy them; by anticipating the future, one knows the means of preparation. Skillful remediation eliminates past abuses; skillful preparation ensures future benefits endure.
This is how the ancient sage kings renewed all under Heaven and left models for later generations.
Later rulers who managed Gu failed to understand the sage's warning of three days before and after Jia; their thoughts were shallow and their focus shortsighted, so they labored to rescue their age yet chaos was not eradicated, and before accomplishments were realized, fresh abuses had already sprouted.
Jia is the head of affairs; Geng is the head of change. For matters of institutional creation and political instruction, one uses Jia to indicate the beginning; for issuing commands and enacting decrees, one uses Geng, as Geng denotes changing and altering.