The Eastern Orthodox and Roman Catholic Churches have the same roots, but very different approaches to how they interpret these roots. The Roman Catholic Church is more focused on law, logic and the central authority of the Pope, while the Eastern Orthodox Church is more concerned with maintaining the mystery of faith and governing through consensus. Ever since the two churches split in the Great Schism of 1054, they have developed diverging theologies related to biblical text, the nature of God, the nature of humans and how they view other religions.
Laws and Texts
Both Eastern Orthodoxy and Roman Catholicism accept the Bible as their sacred text, which contains the same basic books: Old and New Testament, plus additional books called the Deuterocanonicals. In addition to this, however, the Eastern Orthodox Church also accepts a few other books that do not appear in the Catholic Bible, such as Esdras and 3 and 4 Maccabees. The Orthodox Church believes the laws and teachings of the Church can only be altered through council, while in Roman Catholic tradition the Pope, because he's infallible, can alter or create new church law.
Nature of God and the Trinity
Both Orthodox and Roman Catholic tradition espouses the Holy Trinity, which states that God is composed of three parts: the Father, the Son and the Holy Ghost. However, Catholics follow the Nicene Creed, which states that the Holy Spirit comes from the Father "and the Son." Known as the Filioque, this statement caused such theological controversy that it was one of the major reasons for the Great Schism. The Eastern Orthodox Church believes that Jesus was human, should not be considered the same as God and that the Holy Spirit can only come from the Father.
The Eastern Orthodox Church and Roman Catholic Church also differ in their interpretation of human nature, especially when it comes to original sin. Roman Catholicism teaches that the price of Adam and Eve eating forbidden fruit in the Garden of Eden was original sin, which has been passed down to all humans. The Orthodox Church, on the other hand, does not believe in original sin. Instead, they believe the cost of Adam and Eve's disobeying of God in the Garden of Eden is death, which every human inherits. Because of this, each church focuses on different aspects of Jesus' purpose on earth: for Roman Catholics, it is to die for humans' sins; for Orthodox Christians, it is to conquer death.
Roman Catholicism and Eastern Orthodoxy also differ in how they view other religions. Perhaps surprisingly, the Roman Catholic tradition is more open to other versions of Christianity than the Orthodox Church. Although the Roman Catholic Church presents itself as "the one true church," descending directly from St. Peter, it also espouses, "Nevertheless, many elements of sanctification and of truth are found outside [the Catholic Church's] visible confines," including both other Christian denominations as well as other religions. The Orthodox Church, on the other hand, accepts neither other Christian denominations nor other religions as pathways to God. An Orthodox Christian who joins another Christian church is considered apostate.
- Christianity in View: Comparison between Orthodoxy, Protestantism and Roman Catholicism
- The Interactive Bible: List of books in the Christian Bible, Roman Catholic Bible, Greek Orthodox Bible
- OCF.org: What Are the Differences Between Orthodoxy and Roman Catholicism?
- Orthodox Christian Information Center: The Great Schism
- St. Charles Borromeo Catholic Church: Catechism of the Catholic Church, Second Edition
- GOAA: The Fundamental Teachings of the Eastern Orthodox Church
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