The advantage of a theocracy is that all members of the society theoretically share a set of common values and traditions and are compelled to obey the chief ruler, who is considered immortal and infallible. This helps ensure a cohesive society. The disadvantages include a susceptibility to abuse by unscrupulous persons and the marginalization or persecution of people who don't share the faith.
Theocracy is the oldest form of government. In the ancient world, the supreme ruler was believed to have direct contact with a god. The Jews believed that their god appeared to Moses in a burning bush and so Moses became the ruler of Israel. Some kings were considered gods themselves, such as the pharaohs of Egypt. China and Japan had theocratic forms of government until 1911 and 1942, respectively, which contributed to insularity as well as domestic consensus. During the Middle Ages, European royalty deferred to the Church. Modern Islamic states are ruled by Sharia, which is religious law. Iran is governed by a supreme leader who appoints the commander of the armed forces, the director of media and other important managers. Iran represents both positive and negative aspects of theocracy; positive aspects include a united center for decision-making in the event of a national crisis, and negative aspects include a disregard for the rights of non-believers.