Divine Right vs Mandate to Heaven
This was in response to a question in Quora which I had answered.
On the face of it both Divine Right of Kings and Mandate of Heaven sound similar of kings justifying their rule with divine sanction and consent, and not accountable to any one except the supreme power above. But unlike Divine Right of Kings, the Mandate of Heaven was not a free ticket to rule, just because you happened to be of royal birth, it came around with a whole lot of conditions.
The basic idea of Mandate of Heaven is that emperors have a right to rule granted by heaven based on their ability to provide good governance, and this was prevalent in China. But here is the catch, unlike Divine Right of Kings, that gave rulers an unconditional right to rule, the Mandate of Heaven explicitly stated that if an emperor is not virtuous or able, he is not fit to rule. This was in sharp contrast to Divine Right of Kings, where it did not matter if you were a tyrant or plain inefficient, you could rule with no questions asked, as long as you were of royal pedigree. As per the Divine Right of Kings, only God can judge whether the king was fit to rule or not. This basically meant, rulers could just about get away with anything, justifying their actions with Divine Sanctions.
The state of monarchy is the supremest thing upon earth, for kings are not only God's lieutenants upon earth and sit upon God's throne, but even by God himself they are called gods.- James I
One more difference is that Mandate of Heaven does not stipulate that a ruler has to be of noble birth, they could be of common birth, and only the actions determine their status. For eg Liu Bang who founded the Han Dynasty came from a peasant family, as was Zhu Yuanzhang who founed the Ming dynasty. It also gave scope to overthrow despotic rulers or those who were plain incompetent. It has it's roots in the History of China, where dynasties came to power overthrowing the previous dynasty, though it was first used in context to the rulers of the Zhou dynasty who came to power overthrowing the Shang Dynasty.
In sharp contrast, under Divine Right of Kings, only God can judge the King, and that means any attempt to depose, or even restrict the powers of the king would be considered as sacrilege. What this effectively did was to make revolt against the King as illegitimate, unlike the Mandate of Heaven, that give people the right to revolt against a despotic or inefficient ruler.