Knowing Both Sides
Knowing one side still leaves uncertainty
Published July 8, 2026 · By Oriens
知彼知己，百战不殆；不知彼而知己，一胜一负；不知彼不知己，每战必殆。
Know the other and know yourself: in a hundred battles, you will not be imperiled. If you do not know the other but know yourself, you will have one victory and one defeat. If you know neither the other nor yourself, you will be imperiled in every battle.
— Sunzi Bingfa · 谋攻 (Chapter 3), 知彼知己，百戰不殆；不知彼而知己，一勝一負；不知彼不知己，每戰必殆。
The Art of War (孙子兵法) is a Chinese military treatise attributed to Sun Tzu (Sunzi), a military strategist from the Spring and Autumn period (c. 6th–5th century BCE). Its thirteen chapters cover strategy, tactics, and military intelligence.
The passage does not promise certainty. It contrasts knowing both sides, knowing only oneself, and knowing neither. Its useful modern lesson is epistemic modesty: assess your own position and the situation before acting, while remembering that people are not enemies to be classified or controlled.
Know the other and know yourself: in a hundred battles, you will not be imperiled.
This passage appears in the Mougong (谋攻, “Attack by Stratagem”) chapter of the Sunzi Bingfa. It sets out a three-part comparison: knowledge of both sides, knowledge of oneself alone, and knowledge of neither. The sequence matters. Sun Tzu does not say that self-knowledge comes first; the paired assessment is presented as the strongest case.
Self-knowledge and knowledge of the other are placed on equal footing. Neither is primary. A commander who understands only their own forces remains exposed, because the opponent’s disposition, resources, and intentions are part of the same decision. The paired formulation resists any reading that would reduce strategy to introspection alone.
The original setting is military conflict. That setting should remain visible when the line is read today. A contemporary reader may take it as a prompt to distinguish observation from assumption, but not as permission to treat colleagues, loved ones, or strangers as adversaries or to gather information without consent.
Better judgment begins by naming what is known, what is inferred, and what remains unknown. A decision made with only one side of a situation in view is fragile. When both sides are considered, not every outcome becomes predictable, but the quality of the decision itself improves.