If it is to your advantage, make a forward move; if not, stay where you are.
This is repeated from [XI. § 17]. Here I feel convinced that it is an interpolation, for it is evident that [§ 20] ought to follow immediately on [§ 18]. For 動, the T‘ung Tien and Yü Lan have 用. Capt. Calthrop invents a sentence which he inserts before this one: “Do not make war unless victory may be gained thereby.” While he was about it, he might have credited Sun Tzŭ with something slightly less inane.
20. 怒可以復喜愠可以復悅
Anger may in time change to gladness; vexation may be succeeded by content.
According to Chang Yü, 喜 denotes joy outwardly manifested in the countenance, 悅 the inward sensation of happiness.
21. 亡國不可以復存死者不可以復生
But a kingdom that has once been destroyed can never come again into being;
The Wu State was destined to be a melancholy example of this saying. See p. [50].
nor can the dead ever be brought back to life.
22. 故明君愼之良將警之此安國全軍之道也