The Order of the Hexagrams for Preponderance of the Great says: 'Yi means nourishment; without nourishment, nothing can move; hence it is received with Preponderance of the Great.'
In all things, nourishment precedes completion; completion enables movement; movement brings exceeding: this is why Preponderance of the Great follows Yi. In this hexagram, The Joyous (Lake) is above and The Gentle (Wind) is below; the lake is above the trees, submerging them.
A lake normally nourishes trees with moisture, but here it goes so far as to submerge them, which constitutes the meaning of Preponderance of the Great. Preponderance of the Great means the excess of yang, hence the great exceeds, the exceeding is great, and great affairs exceed.
The virtue and deeds of sages and worthies far exceed ordinary men; all great matters that exceed the ordinary are of this kind.
The sage completely fulfills the human Dao, never exceeding principle; in regulating affairs by the righteous principles of the world, he may at times rectify errors by slightly exceeding the middle, such as exceeding in reverence in conduct, exceeding in sorrow in mourning, or exceeding in thrift in expenditure.
Correcting by slightly exceeding enables one to reach the middle, which is the practical application of seeking the center. What is called 'great exceeding' refers merely to great events among ordinary affairs, not to exceeding principle.
Only because they are great are they rarely seen; because they are greater than what is commonly seen, they are called Preponderance of the Great. For example, the abdication of Yao and Shun, or the punitive expeditions of Tang and Wu, all stemmed from the Dao.
The Dao is never not centered and never not constant; but because worldly people rarely see them, they are called exceeding the ordinary on a grand scale. In Preponderance of the Small, yin exceeds at the top and bottom; in Preponderance of the Great, yang exceeds in the middle.
When yang exceeds in the middle, top and bottom are weak; hence the image of the ridgepole sagging. A ridgepole is taken for its capacity to bear weight; four yang lines gathered in the middle can truly be called heavy.
Nine in the Third Place and Nine in the Fourth Place both take the image of the ridgepole, denoting heavy responsibility. Sagging takes the weakness of the root and tip: strong in the middle while root and tip are weak, hence it sags.
Yin being weak and yang being strong, the noble person flourishes while the petty person declines; hence 'it is advantageous to have somewhere to go and prosper.' A ridgepole (dong) is what people today call a purlin.