The Council of Chalcedon was the culmination of a series of synods that met in the wake of Cyril’s death in 444 amid disputes over his legacy. At the Home Synod at Constantinople in November 448, Eusebius of Dorylaeum instigated the condemnation of Eutyches. After Eutyches appealed the synod’s decision, two inquiries were held in April 449, to investigate whether the minutes of the Home Synod had been falsified and whether Flavian had written his condemnation of Eutyches before the archimandrite had even appeared at the synod. This investigation resulted in the decision to hear Eutyches’s appeal at the second Council of Ephesus (Ephesus II) in August 449, which Emperor Theodosius II had convened to address whatever issues he understood to remain in the Nestorian controversy and affirm the faith of Nicaea and Ephesus I.

The date of this letter is unknown, though it is later than the First Letter to Succensus. It could almost be regarded as the charter of the miaphysite movement that would crystalize after the Council of Chalcedon and persists to the present day. Here Cyril responds directly to a series of questions presented to Succensus by an unspecified person from the camp of the Easterners (so called because they came from the Roman diocese of Oriens or “East”), presumably in response to what he had written in the First Letter to Succensus. Notably all of the questions turn on the issue of what the words “flesh” (sarx) or “become incarnate” (ensarkoō) mean and what they imply about how one should use the language of “nature” (physis) with respect to Christ.

Ambiguum 5 to Thomas is a work of Maximus that stems from his early involvement in the monoenergist controversy discussed in the introduction to Ambiguum 31 to John. In 634 or 635 Maximus undertook interpretations of four key passages in Gregory of Nazianzus (Ambigua 1–4 to Thomas) and one key passage in a letter of pseudo-Dionysius the Areopagite (Ambigua 5 to Thomas). Maximus had already written a much longer series of expositions on difficulties (hence the name “Ambigua”) in Gregory of Nazianzus’s works (Ambigua 6–71 to John). In those he used puzzling passages to develop far-reaching theologies of creation, incarnation, and deification. In the Ambigua to Thomas Maximus exploits the same genre to refute monoenergist positions. Thomas was a monk, but that is all we can say with any certainty of the treatises’ addressee.

This letter was delivered by a delegation of four Egyptian bishops to Nestorius in his residence after the morning service in Constantinople on Sunday, November 30, 430. Cyril had spent the past year building a solid coalition of support for his case against the bishop of the Eastern capital, by sending letters to various bishops in the East, and, most importantly, by sending to Rome a dossier including extracts from Nestorius’s sermons. After ordering the archdeacon Leo (the future pope) to undertake an investigation, Pope Celestine called a synod to meet in Rome in August, which condemned Nestorius’s teaching. He then wrote to Cyril deputizing him to order Nestorius to retract his errors and embrace the common faith of Rome and Alexandria, while leaving somewhat vague the precise contours of this common faith. In November Cyril thus held his own synod in Alexandria that likewise condemned Nestorius’s views and produced the following letter, intended to spell out in greater detail the Christological dogmas to which the bishop of Constantinople must adhere.

Basil of Caesarea (ca. 330–378) spent most of his ecclesiastical career combating what he took to be the triple threat of the Heteroousian theology of Eunomius, the Pneumatomachian theology of Eustathius of Sebasteia, and the modalist theology of Marcellus of Ancyra, in the course of which he played a seminal role in the development of the doctrine of the Trinity declared orthodox at the Council of Constantinople in 381. He has generally not been recognized for his Christological contributions. While it is true that the controversy over Apollinarius emerged in the last few years of his life, he did not leave behind a specifically anti-Apollinarian work as did his fellow Cappadocians Gregory of Nazianzus and Gregory of Nyssa. Nonetheless, Basil’s Christology is important because it is a witness to the Christological concerns in the mid-fourth century before the controversy over Apollinarius came to dominate the Christological agenda in the East for the next generation or two. Unfortunately, his Christology has to be pieced together from various comments scattered throughout his corpus.

This letter comes from a crucial moment in the Nestorian controversy and partially accounts for why the attempted ecumenical council in Ephesus in July 431 was so fractious. The letter was penned at some point after November 30, 430, when Nestorius had received a letter from Celestine calling for him to recant his Christological views, and prior to Nestorius’s sermons in the cathedral on December 6 and 7, since these are referred to in the postscript added later. It was written in response to a letter from John of Antioch, sent earlier in November 430, in which John had distanced himself from Nestorius’s views and encouraged him to comply with the summons from Celestine and Cyril to confess that Mary was Theotokos, “bearer of God.” In other words, although John is usually portrayed as an ally of Nestorius, and eventually became such, at this point he was effectively siding with Celestine and Cyril, leaving the bishop of Constantinople without an ally among the powerful sees of Christendom.

Apollinarius was born ca. 310–315 at Laodicea in Syria. He was the son of an Alexandrian native, also named Apollinarius, who was a grammarian by profession. The elder Apollinarius came to Laodicea to serve the church as a presbyter, and eventually the younger Apollinarius served the same church as a reader. At some point between 328 and 335 both father and son were excommunicated by their bishop, Theodotus of Laodicea, who was a member of the Eusebian alliance and a supporter of Arius, for listening against Christian custom to the recitation of a pagan hymn. Both were soon, however, readmitted to communion after the appropriate penance. In 346 Apollinarius was again excommunicated, this time by the new Laodicean bishop, George, another member of the Eusebian alliance (and later a guiding spirit of the Homoiousian movement), for meeting with Athanasius of Alexandria. It is unclear, however, whether the sentence could be or ever was put into effect. It was probably at this point that Apollinarius and the Alexandrian bishop began a lifelong friendship and sharing of theological sympathies.

This letter, written in 430, represents Nestorius’s reply to Cyril’s Second Letter to Nestorius,1 and so marks the first occasion in which the bishop of Constantinople directly set out his views on the topic of the debate to his Alexandrian counterpart. Although it maintains the degree of formality and graciousness expected of such communications, the letter exhibits a striking sarcasm over Cyril’s long-windedness and a clear rebuke to his meddling in the affairs of the church in the imperial capital. The “actions” threatened at the outset of the letter likely refer to Nestorius’s intention to consider the complaints against Cyril brought to him by the persons expelled from Alexandria who had fled to Constantinople for refuge, also referred to in Cyril’s second letter.

The ecclesiastical condemnation of Apollinarius of Laodicea (ca. 315–392) resulted in few of his writings surviving intact, unless they had been transmitted under the names of church fathers of unimpeachable orthodoxy such as Gregory Thaumaturgus, Julius of Rome, and Athanasius of Alexandria.1 However, fifth- and sixth-century writers such as Theodoret of Cyrrhus, Leontius of Byzantium, Emperor Justinian, and others still had access to more texts than we do today, and in works of Christological polemics they excerpted passages from the writings of Apollinarius to demonstrate his problematic views. Thus more than 150 fragments of Apollinarius are extant, preserved mainly in these polemical tracts. A selection of these fragments is translated here. Though they derive from various writings of Apollinarius about which little or nothing is known, these fragments have been selected because they bring out the most distinctive features of his Christology.2 And yet, since these fragments were quoted by those who preserved them precisely because they were deemed to reveal the most controversial aspects of Apollinarius’s Christology, they must be interpreted with care and caution (particularly 111 and 113).

John of Damascus remains the most significant theologian of the eighth century for those churches of both East and West that accepted the Council of Chalcedon. Although the precise dates of his birth and death are unknown, his lifespan was roughly contemporaneous with the Umayyad caliphate (651–750). Unfortunately, very little is known about him, and what is put forth is complicated by over a dozen late fictional vitae. The most prominent for the tradition is the Life of our Holy Father, John Damascene (BHG 884). Nevertheless, some details of John’s life are consistent. John’s grandfather was commissioned by the Byzantine emperor Maurice (r. 582–602) to collect the taxes for the entire region of Syria; this commission was renewed under the emperor Heraclius (r. 610–641), after a brief period of Persian occupation (614–628). John’s family was somehow involved – accounts vary – in the surrender of Damascus to the Arabs (in 634). John’s father retained his position and is even reported to have been a very close friend of the caliph ‘Abd al-Malik (r. 685–705). John followed his father in the Arab administration. John was well educated and became a monk and a priest.

The Lateran synod of 649 was a deliberate rebuke of imperially backed monothelitism. As the Typos was still in force, the decrees of the synod were thus in direct contravention of imperial policy, a contributing factor to the eventual arrest, exile, and mistreatment of Martin of Rome and Maximus the Confessor. In the aftermath of this persecution, successive bishops of Rome kept silent on the Lateran synod, undoubtedly wishing to avoid further outbreaks of imperial wrath. Tensions between the sees of Rome and Constantinople simmered, as each refused to acknowledge the other.

Jacob of Serugh, who is known as “the Flute of the Holy Spirit and the Harp of the Church,” was an influential West Syriac poet. He was born ca. 451 in Kurtam on the Euphrates. At an unknown date Jacob was appointed regional bishop of Ḥawra, and then in 519 he was consecrated bishop of Baṭnan da-Serugh. He died shortly thereafter, perhaps on November 29, 521 (different dates are found in the sources). Jacob is best known as the author of a large number of metrical homilies: almost 400 survive out of the more than 760 that he is said to have written. These treat a variety of topics, with retellings of biblical passages being by far the most common. With some notable exceptions, such as his Metrical Homily on the Council of Chalcedon, Jacob’s metrical homilies do not in general address directly the tumultuous theological, especially Christological, controversies of his day. This is not, however, the case for the forty or so extant letters by Jacob (some of which are only partially preserved).