Drawing on ancient examples, Sun Tzu states that recruiting highly intelligent insiders as spies secures remarkable feats. Intelligence work is the core of warfare, the fundamental basis for all military maneuvers.
The Mohist scholar Yi Zhi, through Xu Bi (a disciple of Mencius), requested to meet Mencius. Mencius said: “I’d be glad to see him, but I’m still unwell. Once I recover, I’ll go to him – Yi Zhi need not come!”