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.

How did Caesaropapism originate?

According to Metropolitan Kallistos Ware, the historical reality of caesaropapism stems from the confusion of the Byzantine Empire with the Kingdom of God and the zeal of the Byzantines "to establish here on earth a living icon of God's government in heaven."

Why was Caesaropapism important?

Caesaropapism is the idea that the emperor had complete control over the Orthodox Greek Church in the Roman/Byzantine Empire, relegating the church to something like a department of state, subordinate to, rather than independent from, imperial power.