Again, my appreciation to Patti Christensen for organizing the collaborative effort among all of us to prepare for this, and the outline I am using for the "skeleton" of this part of the series is the effort of two of my classmates, Sister Andrew Marie, and Nancy Duey. They both did a fantastic job with the effort they put into condensing the material into a systematic form, and as with the other sections I will be using their outline as the framework to write this article.
The history of Christianity is complex, and it entails a lot of very specific information that addresses key issues and events in the growth and development of the Christian faith. In the particular course, the professor divided that history into four distinct eras, and they each had their own challenges, their own key figures, and each also entailed the development of essential doctrines and schools of thought that impacted Christianity for centuries to come. The purpose of the first part of this is to focus on some key issues from each era.
The first era to be discussed is the era of Patristics, which lasted from roughly the Ascension of Christ until the 9th century AD. This was an era that was shaped by two main things. In the earlier centuries of this era, persecution had an impact on the growth of the Church, and the overarching testimony is its amazing growth and spread despite tremendous adversity from the ruling Roman authorities of the time. As Christianity eventually did "conquer" the Roman Empire and persecution ceased, a new issue came up as the Church was now able to codify its beliefs, and that was the rise of heresies. In this outline, we'll deal with those first, and then come back to the effects of persecution.
Heresies tended to bear both good and bad fruit. The bad fruit was that many people embraced doctrines and practices that were in contradiction to what the Bible and the Church held, and therefore many people either left on their own accord as a result or they were excommunicated and condemned for that heresy. However, the good fruit of heresy is that it helped the Church define her doctrines better, and therefore the scourge of heresy may have been used of God to give the Church an idea of what she truly believed, as well as weeding out "tares" in the "field of harvest." There are at least three major heresies that were addressed by major Ecumenical Councils that were called in the 4th and 5th centuries, and those are the source of the discussion now.
The first major council that dealt with issues of doctrine was the Council of Nicaea which was convened in AD 325. The main purpose of this council was to address a new heresy that was being spread by a bishop named Arius, and that heresy entailed two different aspects. Arius (250-336AD) was actually a presbyter of the Church in Alexandria, and in 318 he began to trigger controversy over his unorthodox views on the Trinity (Prokurat, Golitzin, and Peterson, ed. Historical Dictionary of the Orthodox Church. Lanham, MD: Scarecrow Press, 1996. p. 42). Therefore, the heresy of Arius focused on how we understand three Persons being in one God. The problem was complicated by not so much common convictions of the time, but rather how they were articulated - the East, for instance, emphasized the distinction of the three Persons. While correct in doing that, the weakness here was in the formulation; it was couched in language that made the Persons of the Godhead subordinate rather than equal. Likewise, in the West, the problem was not how the West believed - the West rightly emphasized the unity of the Godhead. But, there was a problem here as well - the West's language in articulation of that essential fact could be weakened potentially in that it could insinuate splitting the Godhead into three separate beings (or tritheism) rather than keeping them as one. Arius's approach to the problem was to take away the deity of Christ the Son, which led to outright heresy and rightly garnered condemnation. Arius's reasoning was that the Son was created by the Father to serve as the latter's instrument in creation and redemption (ibid.). This centered as well around the term Homouisios, which articulated that the Father and Son were of the same substance, an idea that Arius had problems with and that his issues garnered support for him from many Alexandrians. However, the language of the Homouisios was adopted in AD 381 at the Council of Constantinople, and this was incorporated into what is commonly called the Nicene Creed that many of us confess at Mass every Sunday. The one important thing about heresies is that they never are original, and they tend to emerge in different forms in later centuries - we then call the resulting movements cults. In the case of the Arian heresy, it has resurrected in the past couple of centuries in the form of a number of cultic groups, and here are some examples. In the Mormon religion, for instance, they teach that the three Persons of the Godhead are three separate beings, and that God is only an exalted man, and the Holy Spirit is depersonalized totally - The Holy Spirit is subordinate to Jesus, but Jesus is subordinate to the Father (Mark J. Cares, Speaking the Truth in Love to Mormons. Milwaukee, WI: Northwestern Publishing, 1993. p. 273). This is articulated in Mormon theology as what is called the "Adam/God Doctrine." Jehovah's Witnesses likewise hold to some Arian convictions, including that Jesus pre-existed as Michael the Archangel, and is thus a created being - he is for Jehovah's Witnesses, the Son of God but not God the Son (Everett Hullum, ed. Beliefs of Other Kinds. Atlanta: Southern Baptist Home Mission Board, 1983. p. 81). Another cult, the Way International, denies Jesus's preexistence and says that the Council of Nicaea in AD 325 was the result of "pagan influence," and thus they also deny Christ is God and the Holy Spirit is a person (Hullum, p. 92). Another group that also carries on the Arian heretical tradition is the Unitarian-Universalist Church, which doesn't view Jesus as divine, and therefore there is no salvation in Christ according to them (Hullum, p. 60). Unitarians are perhaps the most Arian of all these cults, in that much of their own theology can be traced back to the 16th-century Spanish Arianist Servetus. The views of Arius, however, are rightly condemned by all actual Christian traditions - Catholic, Protestant, and Orthodox. We owe much today to St. Athanasios, as well as the Armenian Saint Gregory Nazianzus, for rescuing the Church from Arius and his heretical teachings, and they were instrumental in getting the Council of Constantinople to codify orthodox Trinitarianism as well as the deity of Christ in the Creeds.
The next major issue that arose involved the question of how Jesus could be both fully human and fully divine, and this would lead to a codification of the hypostatic union of Jesus as both human and divine at the Council of Ephesus in AD 431. Again, the question centered around how two theological schools within the Church defined the doctrine. The Alexandrian School, for instance, emphasized a close union between Christ's divinity and His humanity, while the Antiochene School emphasized a distinction between the two natures to avoid confusion. In the midst of this debate rose a bishop of Ephesus named Nestorius, who was a pupil of the more orthodox Assyrian Theodore of Mopsuestia, but Theodore was weak in his explanation of the completeness of Christ's humanity, which cast doubt over the hypostatic union of Christ as fully human and fully God. In AD 428, Nestorius denied that the Virgin Mary could rightly be called the Theotokos, and thus should only be considered the Christotokos (Prokurat, Golitzen, and Peterson, p. 85). Many Alexandrians were converts to Nestorius's views, and it caused such a problem that in AD 431 the Council of Ephesus was called to address the issue. The Council condemned Nestorius's view that Mary was only the mother of Christ's human nature and not His divine nature, and affirmed Mary as the Theotokos and mother of the person Jesus, who is fully God and fully man. Nestorius's followers, mostly in Mesopotamia and largely ethnic Assyrians, formed their own Church at that point which today is still known as the Assyrian Church of the East. However, as a positive note, in 1995 Pope St. John Paul II and the Assyrian Catholicos Mar Khananiah Dinkha signed a Common Christological Agreement which established a sort of Communio in Sacris between both Churches, and for the most part the Assyrian Church now accepts orthodox Christology.
The third major issue was related to Christology but sort of went opposite of Nestorius, and this led to an issue that was addressed at the Council of Chalcedon in AD 451. That council centered around the teachings of Eutyches, an archimandrite of the Church in Constantinople who advocated a union of God and man in Christ (Prokurat, Golitzen, and Peterson, p. 85). Although Eutyches was a very vocal opponent of Nestorius at the Council of Ephesus, he went to the other extreme of even denying Jesus was truly human, but rather a unique "God-man" who transcended humanity. His followers would later be called "Monophysites" and would encompass a large portion of the Syriac-speaking Christian community (Western Assyrians), the Armenians, the Copts in Egypt, and their daughter Churches in Ethiopia, India, and Georgia (although Georgia later accepted the Chalcedonian decision). Prokurat and cohort in their text say though that this was not so much a heresy as it was a schism, and in 1973 the Coptic Pope Shenouda III signed a common Christological agreement with Pope Paul VI, and for the most part the "Oriental" Churches today embrace a more orthodox Christology as a whole. Much of the credit for clarifying the doctrine, however, was to go to Pope Leo the Great, whose response to Eutyches served as the basis for the doctrinal definition of the Council.