Chapter 2626장
Zhongyong (The Doctrine of the Mean) It begins: "What Heaven decrees is called the nature. Following the nature is called the way. Cultivating the way is called teaching." Of the Four Books it is the one that reaches furthest.
The first half gathers the words of Confucius to say why the mean is so hard — all under heaven can be governed evenly, rank and pay can be declined, a bare blade can be trodden on, and still the mean cannot be done. The second half turns on truth alone, saying that truth is the way of Heaven and making oneself true is the way of man, and it goes at last to standing third beside Heaven and earth.
The saying "where another is able in one try, I make it a hundred; where another is able in ten, I make it a thousand" comes from here too.
誠者自成也，而道自道也。誠者，物之終始。不誠無物。是故君子誠之爲貴。誠者，非自成己而已也。所以成物也。成己仁也。成物知也。性之德也，合外內之道也。故時措之宜也。
Truth is what completes itself, and the way is what walks itself. Truth is the end and the beginning of things. Without truth there is no thing. So the gentleman holds the making of truth dear.
Truth does not stop at completing oneself. It is that by which things are completed. Completing oneself is benevolence. Completing things is knowing. This is the virtue of one's nature, and it is the way that joins the outer and the inner. So wherever it is set in its time, it is fitting.