The Great Schism in Christianity was primarily caused by a combination of theological disagreements, cultural differences, and political conflicts between the Eastern (Orthodox) and Western (Catholic) branches of Christianity. Key issues included the pope's authority, the use of unleavened bread in the Eucharist, and the filioque clause regarding the Holy Spirit's procession. The schism formally occurred in 1054 when mutual excommunications were declared by Cardinal Humbert and the Patriarch of Constantinople, Michael I. These disagreements were exacerbated by historical tensions and the cultural divide between the Latin-speaking West and the Greek-speaking East, leading to the enduring split between the Roman Catholic and Eastern Orthodox Churches.