- 五間之事主必知之知之必在於反間故反間不可不厚也
- 昔殷之興也伊摯在夏周之興也呂牙在殷
25. The end and aim of spying in all its five varieties is knowledge of the enemy;
I have ventured to differ in this place from those commentators — Tu Yu and Chang Yu —— who understand 主 as 人主, and make 五間之事 the antecedent of 將 (the others ignoring the point altogether). It is plausible enough that Sun Tzŭ should require the ruler to be familiar with the methods of Spying (though one would rather expect 將 “general” in place of 主) But this involves taking 知之 here in quite a different way from the 知之 immediately following, as also from those in the previous sentences. 之 there refers vaguely to the enemy or the enemy’s condition, and in order to retain the same meaning here, I make 主 a verb, governed by 五間之事. Cf. XI. §19, where 主 is used in exactly the same manner. The sole objection that I can see in the way of this interpretation is the fact that the 死間, or fourth variety of spy, does not add to our knowledge of the enemy, but only misinforms the enemy about us. This would be, however, but a trivial oversight on Sun Tzŭ's part, inasmuch as the “doomed spy” is in the strictest sense not to be reckoned as a spy at all. Capt. Calthrop, it is hardly necessary to remark, slurs over the whole difficulty.
and this knowledge can only be derived, in the first instance, from the converted spy.
As explained in §§22—24. He not only brings information himself, but makes it possible to use the other kinds of spy to advantage.
Hence it is essential that the converted spy be treated with the utmost liberality.
26. Of old, the rise of the Yin dynasty
Sun Tzŭ means the 商 Shang dynasty, founded in 1766 BC. Its name was changed to Yin by 盤庚 P‘an Kêng in 1401.
was due to I Chih
Better known as 伊尹 I Yin, the famous general and statesman who took part in Ch‘êng T‘ang's campaign against 桀癸 Chieh Kuei.
