Caesaropapism is an idea where the head of state is also the head of church. The phrase "Caesaropapism" is thought to have been coined by Justus Henning Böhmer in the 18th century; however, its origin has roots dating to ancient Rome and beyond. Throughout human history there are two central powers which emerge in human society, secular ruler (king) and ecclesiastical ruler (priest). According to the New Catholic Encyclopedia, ancient world rulers often held religious as well as secular duties. In order to understand the origin of Caesaropapism, it is important to acknowledge the role of the king-priest or more appropriately, the Great priest of ancient Rome. In 63 BC, Julias Caesar held the title of Emperor and of Pontifex maximus (Great Priest). This involvement of secular rule within the church continued on with Emperor Constantine, the first Christian Emperor, who thought it was his duty, his sovereign right to involve himself and rule on church matters. So, while history shows an ebb and flow movement between extreme and less extreme examples of Caesaropapism, it is clear this concept continued to develop in both East and West cultures.
Caesaropapism is the idea of combing the power of the government with the religious power. This term may have been coined by Justus Henning Bohmer but the origin may have been in ancient Rome. For example, the emperor is the head of the empire, but is also the head of the church.