If we are going to try to understand why the Church of the East became known as ‘Nestorian’ and what it meant by that, a note on linguistic terminology is inevitable. Here I am guided by three sources: one my co-author, Chalcedon who has lent me his notes on this; John McGuckin Saint Cyril of Alexandria and the Christological Controversy; and Susan Wessels, Cyril of Alexandria and the Nestorian Controversy. John McGuckin’s, The Westminster Handbook to Patristic Theology, was also very useful. So here goes.
The Council of Constantinople, 381 defined the Trinity as one ousia in three hypostases. ‘Ousia’ is Greek for ‘substance’, ‘hypostasis’ is Greek for ‘person’ – so, the Council understood the Trinity as Three Persons in One substance. Unfortunately, both words, when translated into Latin or English can be defined as simply ‘nature’, that is a universal category, as in the nature of God, or a general type as in the nature of human beings. There is a Syriac word, kyana which corresponds to ousia. The problem comes when we get to ‘hypostasis’
St Cyril, like the rest of the Alexandrian school interpreted hypostasis in a non-Platonic sense as the concrete realisation of the ousia – that is as a person. When Nestorius referred to the actual person, he used the term prosopon, which in Syriac is parsopa, and inserted the term hypostasis (Syriac qnoma) in between ousia and person. Why was that and what did it mean?
Nestorius and Antioch understood hypostasis in an Aristotelian sense as ‘material reality bound up with its species’. So, the hypostasis or qnoma is an individual, but a representative of its species and does not exist just in itself; it is not yet the person or prosopon. For the Antiochenes, the prosopon (or person) is defined as ‘the sum of accidental qualities that make the appearance of the hypostases different.’ That is, for example, hair colour, gender or anything else which would distinguish the person of Jessica from the person of Chalcedon.
Thus, for an Antiochene the word ousia/kyana refers to the general species of human; Hypostasis/qnoma refers to a real and existing human being; and prosopon/parsopa to the appearance of the person. In short (you’ll be glad to know) ‘person’ denotes the external appearance, whilst ‘hypostasis’ denotes the inner reality.
So, when Cyril wrote about the two natures of Christ coming together to form a hypostatic union, he meant that the divine and the human natures formed one person or hypostasis. But for Nestorius, who read the word hypostasis as a pre-personal reality, Cyril was talking about mixing the two natures. For Nestorius an ousia (nature) could not exist in a prosopon (person) without a hypostasis, so he argued that ‘In Christ two natures and two hypostases are united in the prosopon.’ He expanded this into a formula which was used by the Church of the East:
I confess in One Christ two natures without mixing. In his divinity he was brought forth by the Father, in his humanity by the Holy Virgin.
As the formulation by Babai the Great (551-628) of the Creed of the Church of the East has it:
One is Christ, the Son of God, glorified by all in two natures; begotten by the Father without beginning before time; born of Mary in his humanity, united in the fullness of time in one body. His divinity is not of the nature of the mother, nor is humanity of the nature of the Father. The natures are preserved in their qnome (hypostases) in one person of the one sonship.’
Of course, for Cyril and the majority who supported him, Nestorius’ formulation of ‘two hypostases’ meant ‘two persons’ – which was condemned, rightly, as heretical. Ephesus condemned not only Nestorius, but the Antiochene School as heretical. More than a dozen Antiochene bishops were deposed, and those who were persecuted fled eastwards into Persia – carrying with them the Nestorian version that, misunderstanding Cyril’s use of language, saw him as the heretic. From that much harm would flow.