The differences between the Greek Orthodox and Roman Catholics are very extensive so I am going to hit on a several topics I believe are important. A major factor is the simple fact that the Western Church spoke and wrote in Latin, versus the Eastern Church who spoke Greek (Walker, 1985, p. 89). The Roman Catholic Church has a Pope who has universal jurisdiction over the entire Church. This is not true in Easter Orthodoxy because they believe in first among equals. The filioque clause was the famous cause of the Great Schism of 1054. This was a modification to the Niceno-Constantinopolitan Creed (Creighton, 1999, p. 407). The question was whether the Holy Spirit proceeds from the Father, or from the Father and the Son. For the Catholics, it is important that the phrase is used; for the Orthodox, it is breaking with tradition and perverting the doctrine of the Trinity (Creighton, 1999, p. 407). There is a difference between church unities as well. You have to ask the question, “What is necessary for the Church to be one?” For the Roman Catholics, it means the organization is headed by the pope. For the Orthodox, it means membership in one of the Orthodox churches. When it came to marriage there were also differences. In the Roman Catholic Church, priests were not a loud to be married. For the Eastern Orthodox, married men may become priests, but not bishops (FitzGerald, 1998, p. 888). There are several differences between the Greek Orthodox and Roman Catholics