The Mandate of Heaven is a Chinese political ideology that was used in Ancient China and Imperial China to legitimize the rule of the king or emperor of China. According to this doctrine, Heaven bestows its mandate on a virtuous ruler. This ruler, the Son of Heaven, was the supreme universal monarch, who ruled Tianxia. If a ruler was overthrown, this was interpreted as an indication that the ruler was unworthy and had lost the mandate. It was also a common belief that natural disasters such as famine and flood were divine retributions bearing signs of Heaven's displeasure with the ruler, so there would often be revolts following major disasters as the people saw these calamities as signs that the Mandate of Heaven had been withdrawn. The Mandate of Heaven does not require a legitimate ruler to be of noble birth, depending instead on how well that person can rule.