High Middle Ages

===Christian Church===
{{Main|Christianity in the Middle Ages}}
The [[East–West Schism]] of 1054 formally separated the Christian church into two parts: [[Roman Catholicism]] in Western Europe and [[Eastern Orthodoxy]] in the east. It occurred when [[Pope Leo IX]] and [[Michael Cerularius|Patriarch Michael I]] [[excommunication|excommunicated]] each other, mainly over disagreement over the [[filioque]], an addition to the creed concerning the origin of the Holy Spirit, as well as disputes as to the existence of papal authority over the four Eastern [[patriarch]]s, use of unleavened bread in the liturgy, and fasting days.