Caesaropapism /ˌsiːzəroʊˈpeɪpɪzəm/ is the idea of combining the power of secular government with the religious power, or of making secular authority superior to the spiritual authority of the Church; especially concerning the connection of the Church with government. Justus Henning Böhmer (1674-1749) may have originally coined the term (Cäseropapismus).Max Weber (1864-1920) wrote: "a secular, caesaropapist ruler... exercises supreme authority in ecclesiastic matters by virtue of his autonomous legitimacy". According to Weber's political sociology, caesaropapism entails "the complete subordination of priests to secular power."
In its extreme form, caesaropapism is a political theory in which the head of state, notably the Emperor ("Caesar", by extension a "superior" king), is also the supreme head of the church (papa, pope or analogous religious leader). In this form, caesaropapism inverts theocracy (or hierocracy in Weber) in which institutions of the Church control the state. However, both caesaropapism and theocracy are systems in which there is no separation of church and state and in which the two form parts of a single power-structure.
Caesaropapism's chief example is the authority the Byzantine (East Roman) Emperors had over the Church of Constantinople or Eastern Christian Church from the 330 consecration of Constantinople through the tenth century. The Byzantine Emperor would typically protect the Eastern Church and manage its administration by presiding over Ecumenical Councils and appointing Patriarchs and setting territorial boundaries for their jurisdiction. The Emperor exercised a strong control over the ecclesiastical hierarchy, and the Patriarch of Constantinople could not hold office if he did not have the Emperor's approval. Eastern men like St. John Chrysostom, Patriarch of Constantinople and St. Athanasius, Patriarch of Alexandria, strongly opposed imperial control over the Church, as did Western theologians like St. Hilary and Hosius, Bishop of Córdoba. Such Emperors as Basiliscus, Zeno, Justinian I, Heraclius, and Constans II published several strictly ecclesiastical edicts either on their own without the mediation of church councils, or they exercised their own political influence on the councils to issue the edicts.