In the state cult of the Han dynasty, Heaven was the supreme deity, a deity which was believed to guide the fate of the world directly. The emperor, or Son of Heaven, was its representative and ruled by its favor. A dynastic founder, as the first recipient of Heaven's mandate, was chosen over all others for his personal merit. The last emperor of a dynasty lost the mandate, because he and his house were no longer fit to rule. The coming of the mandate was heralded by auspicious omens, the decline of Heaven's favor was announced by portents.

The belief in the Mandate of Heaven deeply influenced Chinese historiography. The ancient historians quoted, suppressed, twisted, and even falsified evidence to show why the dynastic founder had been worthy of Heaven's blessing, a worthiness about which he personally had no doubt. His emphasis was on legitimacy. Those who unsuccessfully opposed the mandate were manifestly inferior men, whose lack of moral caliber was borne out by their fates. There the ancient historian leaned in the opposite direction: He wrote biased biographies for the most important rebels and pretenders, who by their actions had placed themselves outside ordered society. Further he did not go; no additional biographies were compiled for the chief assistants of those who had turned against the legitimate dynasty.

This is the historiographical situation, which is a major obstacle to a fair assessment of such men as Wang Mang, who overthrew the Former Han house and attempted to found his own dynasty.