but cannot make certain of defeating the enemy.
The original text reads 使敵之可勝, which the modern text has further modified into 使敵之必可勝. Capt. Calthrop makes out the impossible meaning, “and further render the enemy incapable of victory.”
4. 故曰勝可知而不可爲
Hence the saying: One may know how to conquer without being able to do it.
Capt. Calthrop translates: “The conditions necessary for victory may be present, but they cannot always be obtained,” which is more or less unintelligible.
5. 不可勝者守也可勝者攻也
Security against defeat implies defensive tactics; ability to defeat the enemy means taking the offensive.
For 不可勝 I retain the sense which it undoubtedly bears in [§§ 1–3], in spite of the fact that the commentators are all against me. The meaning they give, “He who cannot conquer takes the defensive,” is plausible enough, but it is highly improbable that 勝 should suddenly become active in this way. An incorrect variant in the Yü Lan is 不可勝則守可勝則攻.
6. 守則不足攻則有餘
Standing on the defensive indicates insufficient strength; attacking, a superabundance of strength.