The Art of War

(6th century BC)

• "知彼知己，百戰不殆；不知彼而知己，一勝一負；不知彼，不知己，每戰必敗"
  • Source: Chapter 3, the last sentence.
  • Translation: "If you know others and know yourself, you will not be imperiled in a hundred battles; if you do not know others but know yourself, you win one and lose one; if you do not know others and do not know yourself, you will be imperiled in every single battle."