New Emeline wrote:Both my parents' families are Adventist, so that's really the only subset of Christianity I'm familiar with. What are the major differences between all the denominations, and how much do they matter?
That would be a huge post, so I'll just cover the ones I'm most familiar with, which would be Roman Catholicism, Eastern Orthodoxy, and the Oriental Communion.
What the three have in common is that they agree with the belief in Apostolic tradition as the basis of the faith, as well as the belief in episcopal administration in which bishops who are appointed by previous bishops in a line going back to one of the original Apostles run the church.
Here are some of the main differences
Roman Catholicism believes that the Pope of Rome, as the successor of Saint Peter, is the head of the Church and Vicar of Christ on Earth. As such, the Pope of Rome has absolute power in administration and theoretically in belief. The Roman Catholic Church believes that the Holy Spirit proceeds from the Father and the Son. They follow the Council of Chalcedon in believing that Christ has two natures in union which are Human and Divine. The Roman Catholic Church traditionally is very Aristotlean and Platonic in its philosophy. The Catholic Church believes in evolution of theology over time. They also believe in the Beatific Vision, in which the believer sees God in Heaven.
Eastern Orthodoxy is instead run on a national level, with each national church being run by a council of bishops. The Orthodox Church generally believes that theology shouldn't change, but that practices should be as close to those of the ancient church as possible. It believes that the Holy Spirit proceeds from the Father alone, and also follows the Council of Chalcedon and its beliefs on the natures of Christ. The Orthodox Church is typically not as rationalistic in its belief system as the Catholic Church, and is instead very mystical in its outlook. Unlike the Catholic belief in the Beatific vision, Orthodox believe in 'Theosis', by which the believer is permeated by God's divine energy and experiences union with God in this way. Likewise, the Orthodox don't believe in Hell as a place of suffering, but rather as the experience of God's energies by those who don't want to experience it.
Oriental Orthodoxy is run similarly to the Eastern Orthodox Church. The Oriental Communion rejects the Council of Chalcedon, and instead believes in the doctrine of Miaphysitism, where Christ has one nature, which is a union of divinity and humanity. In terms of philosophy, it's very similar to the Eastern Orthodox Church. There are differences in the idea of Theosis according to the late Pope Shenouda of Alexandria, but I'm not smart enough to get into the esoteric differences he points out.
As far as whether it matters: The Church which is truly the one founded by Christ and the Apostles is infallible in its belief as the gates of Hell cannot triumph over it. So, yeah, it matters.