Knowledge of the enemy’s dispositions can only be obtained from other
men.
Mei Yao-ch‘ên has rather an interesting note: 鬼神之情可以筮卜知形氣之
物可以象類求天地之理可以度數驗唯敵之情必由間者而後知也 “Knowledge of the
spirit-world is to be obtained by divination; information in
natural science may be sought by inductive reasoning; the laws of
the universe can be verified by mathematical calculation: but the
dispositions of an enemy are ascertainable through spies and spies
alone.”