Oriental Orthodoxy refers to the faith of those Eastern Christian Churches that recognize only three ecumenical councils — the First Council of Nicaea, the First Council of Constantinople and the First Council of Ephesus. They rejected the dogmatic definitions of the Council of Chalcedon (451). Hence, these Oriental Orthodox Churches are also called Old Oriental Churches or Non-Chalcedonian Churches. Despite the potentially confusing nomenclature (Oriental meaning eastern), Oriental Orthodox churches are distinct from those that are collectively referred to as the Eastern Orthodox Church. The Oriental Orthodox communion comprises six groups: Coptic Orthodox, Ethiopian Orthodox, Eritrean Orthodox, Syriac Orthodox, Malankara Orthodox Syrian Church (India) and Armenian Apostolic churches. These six churches, while being in communion with one another, are hierarchically independent. The Oriental Orthodox Church and the rest of the Church split over differences in Christological terminology. The First Council of Nicaea (325) declared that Jesus Christ is God, “consubstantial” with the Father; and the First Council of Ephesus (431) that Jesus, though divine as well as human, is only one being (hypostasis). Twenty years after Ephesus, the Council of Chalcedon declared that Jesus is in two complete natures, one human and one divine. Those who opposed Chalcedon likened its doctrine to the Nestorian heresy, condemned at Ephesus, that Christ was two distinct beings, one divine (the Logos) and one human (Jesus).
Oriental / African Orthodox Christians do not believe in One Nature, but rather Two distinct natures that are unified in One Person of the Trinity (i.e. the Son). These two natures always exist in Christ and He is never alienated from His Divinity – This is the most important point. Oriental / African Orthodox were believed to fundamentally differ from the Catholics and the Greek Orthodox in that unlike us, the Catholics and others believed that Christ was at times human (e.g. when He wept or when He died)and at times divine. We maintained and maintain that Christ never changed his nature. He was always human and divine. He as G-d freely took on the human attribute of mortality and then flung off the attribute of death at His divine will to resurrect and transform our flesh gotten from St. Mary unto eternal life. We too believe in two natures, but we believe in the constancy of Christ’s nature (i.e. it does not change).