Frederick concludes his chapter on spies with the words: “Zu allem diesem füge ich noch hinzu, dass man in Bezahlung der Spions freygebig, ja verschwenderisch seyn muss. Ein Mench, der um eures Dienstes halber den Strick waget, verdienet dafür belohnet zu werden.” In no other business should greater secrecy be preserved. Tu Mu gives a graphic touch: 出口入耳也, that is to say, all communications with spies should be carried on “mouth-to-ear.” Capt. Calthrop has: “All matters relating to spies are secret,” which is distinctly feeble. An inferior reading for 密 is 審. The following remarks on spies may be quoted from Turenne, who made perhaps larger use of them than any previous commander: “Spies are attached to those who give them most, he who pays them ill is never served. They should never be known to anybody; nor should they know one another. When they propose anything very material, secure their persons, or have in your possession their wives and children as hostages for their fidelity. Never communicate anything to them but what it is absolutely necessary that they should know.”[187] 15. 非聖智不能用間 Spies cannot be usefully employed This is the _nuance_ of Tu Yu’s paraphrase 不能得間人之用. without a certain intuitive sagacity. Mei Yao-ch‘ên says: 知其情僞辨其邪正則能用 “In order to use them, one must know fact from falsehood, and be able to discriminate between honesty and double-dealing.” Wang Hsi takes 聖 and 智 separately, defining the former as 通而先識 “intuitive perception” and the latter as 明於事 “practical intelligence.” Tu Mu strangely refers these attributes to the spies themselves: 先量間者之性誠實多智然後可用之 “Before using spies we must assure ourselves as to their integrity of character and the extent of their experience and skill.” But he continues: 厚貌深情險於山川非聖人莫能知 “A brazen face and a crafty disposition are more dangerous than mountains or rivers; it takes a man of genius to penetrate such.” So that we are left in some doubt as to his real opinion on the passage. 16. 非仁義不能使間 They cannot be properly managed without benevolence and straightforwardness. Chang Yü says that 仁 means “not grudging them honours and pay;” 義, “showing no distrust of their honesty.” “When you have attracted them by substantial offers, you must treat them with absolute sincerity; then they will work for you with all their might.” 17. 非微妙不能得間之實 Without subtle ingenuity of mind, one cannot make certain of the truth of their reports. Mei Yao-ch‘ên says: “Be on your guard against the possibility of spies going over to the service of the enemy.” The _T‘ung Tien_ and _Yü Lan_ read 密 for 妙. 18. 微哉微哉無所不用間也 Be subtle! be subtle! Cf. VI. § 9: 微乎微乎. Capt. Calthrop translates: “Wonderful indeed is the power of spies.” and use your spies for every kind of business. 19. 間事未發而先聞者間與所告者皆死