What was the Mandate of Heaven, and how could a dynasty lose it?

The Mandate of Heaven was the idea that an emperor ruled because Heaven allowed it, and that Heaven could stop allowing it. It was a political doctrine used in ancient and imperial China to legitimize the rule of the king or emperor. According to it, Heaven bestows its mandate on a virtuous ruler, called the Son of Heaven, who rules all under heaven.

The catch is that the mandate was conditional. Retaining it depended on the just and able performance of the rulers and their heirs. So an overthrow was read as a verdict: if a ruler was toppled, that showed he and his dynasty were unworthy and had lost the Mandate. Natural disasters, such as famine and flood, were seen as signs of Heaven's displeasure, and revolts often followed major disasters because people took the calamities as a sign that the mandate had been withdrawn.

This also meant the doctrine did not require noble birth. The Han and Ming dynasties were founded by men of common origins, yet they were seen as having succeeded because they had won the Mandate. And it gave philosophers and scholars a lever: they often invoked it to curtail the abuse of power by rulers in a system with few other checks.

The idea began with the Zhou, who used it to justify overthrowing the earlier Shang dynasty. They believed that the Shang had become morally corrupt, and that the loss of virtue entitled their own house to take over. Later winners kept using it: Chinese historians interpreted a successful revolt as evidence that Heaven had withdrawn its mandate from the ruler.