Hence it is only the enlightened ruler and the wise general who will
use the highest intelligence of the army for purposes of spying,
Ch‘ên Hao compares § 15: 非聖智不能用間. He points out that 湯武之聖
伊呂宜用 “the god-like wisdom of Ch‘êng T‘ang and Wu Wang led them
to employ I Yin and Lü Shang.” The _T‘u Shu_ omits 惟.
and thereby they achieve great results.
Tu Mu closes with a note of warning: 夫水所以能濟舟亦有因水而覆沒者間
所以能成功亦有憑間而傾敗者 “Just as water, which carries a boat from
bank to bank, may also be the means of sinking it, so reliance on
spies, while productive of great results, is oft-times the cause
of utter destruction.”
Spies are a most important element in war, because on them depends an
army’s ability to move.
The antecedent to 此 must be either 間者 or 用間者 understood from
the whole sentence. Chia Lin says that an army without spies is
like a man without ears or eyes.