Seven hundred years ago, Italian scholar Marsilius of Padua helped lay the foundation for our modern ideas of popular sovereignty. In his book, “Defensor Pacis,” written in the context of an ongoing battle in church-state relations, he anticipated the idea of separate spheres for church and state.
Though tensions over the balance of power between church and state were probably inevitable, it took surprisingly long for them to develop. In the Roman Empire, the state regulated religious practice. Christianity was an illegal religion in the Empire for nearly 300 years, but when legalized, a precedent was set for the church to operate separately from the state. For centuries, the two sides cooperated without much fundamental conflict.
In the Latin West, questions about the relationship between church and state arose at the end of the eighth century. In 799, Pope Leo III was accused of a variety of crimes. He appealed to Charlemagne, the king of the Franks, for judgment. Though unsure whether he had jurisdiction over the Pope, Charlemagne acquitted Leo. Since this suggested Charlemagne was over the Pope, Leo decided to redress the balance by crowning Charlemagne emperor on Christmas of 800, implying papal authority over that office.
After Charlemagne, both the church and the state suffered serious decline for nearly a century. The title of emperor fell into disuse, and the papacy descended into a period of moral degeneracy. In the late 900s, with the aid of church reformers, the Germanic King Otto I managed to centralize enough power to be named Holy Roman Emperor. He and his successors deposed a series of corrupt popes and appointed reformers in their place.
These reforming popes soon found their dependence on the emperor both theologically and politically problematic. Politically, by playing around with the rules and making deals with the emperor’s enemies, they managed to loosen the papacy from imperial control. Theologically, they began to argue that as the eternal is superior to the temporal and the spiritual to the physical, the church is superior to the state and the pope to the emperor. In effect, this meant the church was over the state. The logic was that, since the civil government was established by God to enforce righteousness and the pope was the vicar of Christ on Earth, he should be arbiter of what is righteous and secular rulers must obey. If they failed to do so, the pope claimed the right to depose them, even the Holy Roman Emperor.