The Byzantine Emperor's religious authority was based on the concept of caesaropapism, which held that the Emperor was both the temporal and spiritual leader of the Empire. This meant that the Emperor had the responsibility to protect and defend the Orthodox faith, and to ensure that it was practiced correctly and without heresy. The Emperor also played a role in the selection and ordination of bishops, and he could even depose a Patriarch if he deemed it necessary.
In practice, the relationship between the Emperor and the Patriarch was often complex and dynamic. There were times when the Emperor and Patriarch worked closely together, and times when they were in conflict. However, the overall structure of religious power in the Byzantine Empire remained relatively stable throughout the Empire's history.
Here is a summary of the power structure of the Byzantine Empire in religious matters:
* The Emperor was the head of the Eastern Orthodox Church and had the power to appoint the Patriarch of Constantinople and convene ecumenical councils.
* The Patriarch of Constantinople was the highest religious authority in the Empire and oversaw the other bishops and supervised religious affairs.
* The decisions of ecumenical councils were binding on all members of the Eastern Orthodox Church.
* The Byzantine Emperor's religious authority was based on the concept of caesaropapism, which held that the Emperor was both the temporal and spiritual leader of the Empire.