The Book of Documents, or Shujing (also called the Shangshu, 尚書), is one of the Five Classics: a collection of speeches, proclamations, and counsels the tradition attributes to sage-rulers and early kings, from the legendary Yao, Shun, and Yu to the founders of the Shang and Zhou. Its chapters span very different strata, from an early Zhou core to later, in part forged material. It is one of the foundational textual sources for the Mandate of Heaven — that rule depends on Heaven's conditional approval — above all in its Zhou proclamations, and it shaped Chinese thinking about legitimate rule and its overthrow for two thousand years.
When the Zhou people toppled the Shang kings around three thousand years ago, they faced an awkward question: how is a conqueror any better than the tyrant he replaced? The Book of Documents preserves their answer. In speech after speech, the victors insist they did not seize the throne at all. Heaven took it from a cruel king who had forfeited the right to rule, and handed it to them. It was a brilliant justification, and it carried a hidden blade. The very argument that made the Zhou conquest righteous could be turned, one day, against the house of Zhou itself.