In Iran, both before and after Islam, the ruler was thought to be God's vicegerent on earth and, unlike Europe, his legitimacy was not dependent on the law of primogeniture. Thus he was not bound by any written or unwritten law or tradition and could take decisions up to the utmost of his physical power, the only restraint being the fear of rebellion. He would lose God's Grace and somehow fall from power if he ruled unjustly, but there was no test either for possessing the grace or for losing it except by virtue of holding power or being overthrown. There were thus no rules for succession and rebels could and did claim legitimacy once they were successful. The position both justified and was justified by arbitrary rule, where long-term functional social classes did not exist and history became a series of connected short terms, a sociological phenomenon which still persists in Iranian society.