Roman Catholics and Eastern Orthodox Catholics once comprised a single Christian church with two centers of power, Rome and Constantinople. In 1054, Pope Leo IX, of Rome, declared himself the supreme head of the entirety of Christianity. Leo demanded that the leaders of the Eastern churches of Constantinople acknowledge his authority. When the authorities in Constantinople refused to submit, Leo ended their alliance with the Roman Catholic Church, through orders of excommunication, or banishment from the faith. Known as the Great Schism, this official split between Roman Catholics and Eastern Orthodox Catholics, does not mean they practice Christianity in radically different ways. Belief in the Trinity, reverence for saints, presence of an identifiable leadership and practice of seven Holy Sacraments are commonalities, though there are some variations as noted.

Trinity

Both Roman Catholics and Eastern Orthodox Catholics understand God to exist in three forms, known as the Trinity. God is the Father, Son and Holy Spirit. The Father refers to God’s role as the creator of the world. The Son refers to Jesus. Finally, the Holy Spirit, they believe, enters people's souls during their daily lives.

Saints

Holding reverence for the saints plays a central role in the spiritual lives of Roman Catholics and Eastern Orthodox Catholics. The physical representation of the saints tends to take different forms, however. Roman Catholics usually use statutes to represent their saints; meanwhile, Orthodox Catholics more often use paintings to represent their saints. For Roman Catholics there is a rigid procedure for choosing officially sanctioned saints. This process, known generally as canonization, does not exist in the Orthodox community.

Leadership

The central doctrinal divide between the two Christian churches concerns Papal supremacy. Roman Catholics believe the Pope is the Vicar, or living embodiment, of Jesus. He is thus, in their opinion, the head of the entire Christian religion. Eastern Orthodox Catholics view the Pope as the head of Christianity in Rome, a geographical responsibility. A collection of national churches comprises the Orthodox faith. Each separate church maintains its own supreme leader, often known as a patriarch, and bishops, who comprise the synod, or governing council.

Clergy Celibacy and Divorce

There are differences between Roman Catholics and Eastern Orthodox Catholics when it comes to clergy celibacy and divorce. Roman Catholic priests cannot marry. In contrast, Orthodox priests can be married, if the marriage predates assumption of the priesthood. Unmarried men who join the Orthodox clergy must proclaim a vow of celibacy, similar to all Roman Catholic clergy. Another difference is that the Orthodox Church allows its followers to divorce, unlike Roman Catholic tradition.