“Christology” is the study of the person of Jesus Christ and especially the mystery of the union in Christ of the divine and human natures. The first four ecumenical councils in the 4th and 5th centuries defined the personhood and natures of Christ, and the Nicene Creed we recite on Sundays expresses the official teachings of the Church in the liturgy.
The Council of Nicea (325)
A priest from Alexandria, Arius (250 or 256 -336), taught heretically that Jesus is not God, but only a unique creature. St. Athanasius (ca. 296-373) was the champion who fought against Arianism. When Athanasius was a little boy, his bishop, Alexander, saw him baptizing other children. The bishop discovered Athanasius’ great love for God and splendid talents. He took charge of his education and trained him for the priesthood. At the young age of 25, Athanasius wrote his famous treatise On the Incarnation of the Word of God. When not yet 30, he was the leader at the Council of Nicea. The Council teaches that God the Son is of one substance (consubstantial) with the Father.
Shortly after the Council of Nicea, Athanasius succeeded as bishop of Alexandria. The Arians strived to impose their heretical teachings by influencing imperial authority. Though pressured by the emperor, Athanasius courageously refused to re-admit Arius into communion. During his life, Athanasius was banished five times and spent seventeen years in exile. Cardinal Newman described Athanasius as “a principal instrument after the Apostles by which the sacred truths of Christianity have been conveyed and secured to the world”.
The Council of Constantinople (381)
Arius denied the divinity of Christ, whereas, Apollinaris (ca. 310-390) went to the other extreme by denying the humanity of Christ. Apollinaris was a close friend of St. Athanasius and a stanch defender of Nicea. But in his zeal to refute Arians, he developed a theology which was eventually condemned by the Church.
Apollinaris taught that Christ’s divinity replaced the rational part (i.e. intellect and will) of his human nature. That means Christ is consubstantial with the Father, but not consubstantial with us. The teaching of Apollinaris was condemned by the Council of Constantinople in 381. The Church teaches that Christ has the complete human nature.
The Council of Ephesus (431)
Theodore of Mopsuestia (ca. 350-428) taught that in Christ, there are two persons, the divine person and the human person. His disciple, Nestorius, continued to teach this false doctrine as patriarch of Constantinople. He even preached against the title “Mother of God”.
St. Cyril (ca. 376-444), the patriarch of Alexandria, challenged Nestorius. The role of St. Cyril against Nestorianism was similar to the role of St. Athanasius against Arianism. In 431 the Council of Ephesus condemned the teachings of Nestorius and affirmed that “Emmanuel is truly God, and the holy Virgin is, therefore, Mother of God, for she gave birth in the flesh to the Word of God made flesh.”
The crucial word for the Council of Nicea was “substance”, whereas the crucial word for the Council of Ephesus was “hypostatic”, which means “personal”. In Christ, the divine nature and human nature are united personally.
The Council of Chalcedon (451)
At Alexandria, in opposition to Nestorianism, the monk Eutyches (378-454) taught that after the Incarnation, the human nature was merged in the divine. This heresy is called Monophysitism. The patriarch of Constantinople, St. Flavian, called a synod which condemned Eutyches. Pope St. Leo the Great (ca. 400-461) wrote his classic Dogmatic Letter to Flavian (The Tome of Leo) stating Christ is one person with two natures.
When The Tome of Leo was read at the Council of Chalcedon, the assembled bishops exclaimed, “This is the faith of the Fathers. This is the faith of the Apostles. This is the faith of all of us. Peter has spoken through Leo.”
The Catechism of the Catholic Church summed up the conciliat teachings: “Jesus Christ possesses two natures, one divine and the other human, not confused, but united in the one person of God’s Son.”
尼西亞大公會議The Council of Nicea（325年）
來自亞歷山地亞Alexandria的亞略Arius (250 或 256 -336) 神父 ，提出了「亞略主義Arianism」異端，否認耶穌的天主性，指出耶穌只不過是一位獨特的受造物；而當時衛道熾烈的是聖師亞大納削St. Athanasius (ca. 296-373) 。年幼的亞大納削，被主教亞歷山大Alexander看見替其他小朋友付洗，發覺他極大愛主之心，也看出他是個天才，遂為他提供教導, 育練他成為神父。年僅二十五歲的亞大納削，發表了有關「道成肉身On the Incarnation of the Word of God」箸名的論文。未及三十歲的他，主導著尼西亞大公會議——欽定天主聖子是與聖父同性同體。
尼西亞大公會議後不久，聖亞大納削繼任為亞歷山地亞主教。亞略異端轉向影響當時的權貴，但亞大納削不畏皇權，維持開除亞略神父等人的教籍。聖人五次被放逐，前後共十七年之久。廖文樞機Cardinal John Henry Newman形容聖亞大納削「是繼眾宗徒後，最能把基督神聖的真理，傳遞和保存給普世的人。」
君士坦丁堡大公會議The Council of Constantinople (381年）
當亞略否定基督的天主性時，另邊又產生了否定基督人性的「亞玻林Apollinaris論」異端。 亞玻林 (ca. 310-390) 原是聖亞大納削的好友，雖合力抗衡亞略異端，但他自己卻發展了另一套神學異端——聖言(天主性)在基督內取代了人性靈魂(理智、意志)的位置，有別於我們一般的人性。這異端雖承認基督與天父有同一本性, 卻否認祂與我們有同樣的人性。381年的君士坦丁堡大公會議，否定亞玻林謬論，明言基督也取了一個人完整的理性靈魂, 因而有完全的人性。
厄弗所大公會議The Council of Ephesus（431年）
莫素式亞Mopsuestia的戴多祿Theodore (ca. 350-428) 教授基督有兩個位格的異端。他的門生，聶斯多略Nestorius以君士坦丁堡宗主教身份，推行這異端——「聶斯多略教派Nestorianism（亦即後來傳入中國的景教）」：主張基督有兩位格及兩性體，瑪利亞只是基督人性的母親，並非天主之母。
亞歷山地亞宗主教聖濟利祿St. Cyril (ca. 376-444) ，挑戰聶斯多略，就如聖亞大納削抗辯亞略異端一樣。431年厄弗所大公會議譴責了聶斯多略教派，確認「厄瑪奴爾是真天主，故此，至聖童貞是天主之母，因為她生育了成了血肉的天主聖言。」
325年的尼西亞大公會議的關鍵在於「基督的性體substance」，而431年的厄弗所大公會議則重於「基督的位格hypostatic / personal」。因而，在基督內，完整的天主性和人性是在一個位格Person內結合。
加采東大公會議The Council of Chalcedon (451年）
在亞歷山地亞反對聶斯多略教派聲中，竟然有一位名叫沃迪奇Eutyches (378-454)的隱修士，提出「基督單性論Monophysitism」——主張基督之人性被天主性吸收。君士坦丁堡宗主教聖法萊文St. Flavian馬上召開主教會議，予以駁斥。教宗聖良一世St. Leo the Great (ca. 400-461) 給聖法萊文一封具代表性的信函（良之巨箸Tome of Leo），堅持了基督一位兩性之說。