In 412 Cyril became bishop of the church of Alexandria and all Egypt, succeeding his uncle Theophilus whose episcopacy was famously marked by controversy with the Constantinopolitan church in the person of its bishop, John Chrysostom. Cyril carried forward his uncle’s legacy by entering into a dispute with another bishop of Constantinople, Nestorius, within the first year of the latter’s episcopal tenure in the Eastern capital. Soon after the start of Nestorius’s episcopacy in 428, a local Christological dispute erupted between two groups in Constantinople regarding the propriety of the terms Theotokos (“bearer of God”) and Anthropotokos (“bearer of the human being”) for the Virgin Mary. Nestorius handled the situation by rejecting both terms and proposing that the word Christotokos (“bearer of Christ”) be used instead, though this solution did little to quell the conflict. In early 429 Cyril, claiming that these rumblings in the imperial capital were beginning to cause distress and uncertainty in Egypt, decided to stake out a position in the growing debate by denouncing Nestorius’s Christology in his Festal Letter 17 and Letter to the Monks of Egypt, though without naming Nestorius in either communication.

The Ascension of Isaiah imagines Isaiah’s tour of the seven heavens, the descent of Christ through the divine realms in the form of an angel, and the death of the prophet at the hands of King Hezekiah’s wicked son, Manasseh. This enigmatic work falls into two main parts: the martyrdom of Isaiah (chapters 1–5) and the vision of Isaiah (chapters 6–11). There is no consensus about the date, composition, or provenance of the Ascension of Isaiah. A 1996 monograph on the text stresses the unity of the work and locates it in the second century CE, probably in Syria.1 This all, however, remains disputed.

Timothy Aelurus was the episcopal successor in Alexandria to the luminaries Cyril (412–444) and Dioscorus (444–451). The sobriquet “Aelurus” has been variously interpreted as “the Cat” or “the Weasel,” and it was purportedly bestowed by enemies on account of his ascetical emaciation. A monk in his youth, he was ordained presbyter by Cyril and was in the entourage of Dioscorus at the second Council of Ephesus in 449. After the latter’s deposition at the Council of Chalcedon in 451, Proterius, a Chalcedonian, was installed as bishop of Alexandria. Timothy, however, remained loyal to Dioscorus. When news of Emperor Marcian’s death (on January 26, 457) reached Alexandria in early February, this sparked the anti-Chalcedonian faction to find at long last a replacement for Dioscorus. They chose Timothy, who was consecrated as a rival bishop on March 16, 457, possibly by only two bishops and thus irregularly (since three bishops were required for a canonical ordination as bishop).

The so-called Tome to the Antiochenes was penned by Athanasius of Alexandria and others in connection with the Council of Alexandria in 362. It was sent to the Christians of Antioch to help reconcile two factions there with longstanding differences and rival bishops. The first group was the “Meletians,” supporters of Meletius, who was consecrated bishop of Antioch in 361 with the support of Eudoxius, bishop of Constantinople. Meletius had had some association with the imperially backed Homoianism of the late 350s, but by 361 was seen as Homoiousian-leaning – the public expression of which views got him exiled soon after his consecration.1 The other group was the “Eustathians,” Nicene supporters of the long-dead Eustathius, who had been deposed as bishop of Antioch in 327. The leader of the Eustathians in the 360s was Paulinus, who was consecrated as bishop of Antioch by Lucifer of Cagliari in 361. Paulinus was supported by the bishop of Rome – and Athanasius himself – as the rightful bishop. Accordingly, the Tome was addressed to the Meletians, whom Athanasius viewed as once tainted by Arianism but, as Homoians leaning toward Homoiousianism, potential allies for the Nicene cause.

Under the leadership of Timothy II Aelurus (bishop of Alexandria 457–477) the anti-Chalcedonian Church solidified communally, geographically, and theologically. The condemnation and exile of his predecessor, Dioscorus, spurred Timothy to successfully rally nearly all Egyptian bishops and priests against the Chalcedonian Definition and in favor of language pertaining to the double consubstantiality of Christ. That is, Christ was both same-in-substance with God and same-in-substance with human beings. However, the rise of Timothy’s anti-Chalcedonian Church in Egypt did not faze the emperors Marcian (r. 450–457) and Leo I (r. 457–474); their respective reigns saw no attempts to reconcile. It was Emperor Zeno (r. 474–491), with the support of Bishop Acacius of Constantinople, who intended to secure a reconciliation between the imperial Chalcedonian Church and the Egyptian anti-Chalcedonian Church.

A gem of early Christian oratory, Proclus’s first homily on the Holy Virgin draws on the emerging tradition of festal homilies such as we see in Basil of Caesarea’s Homily on the Holy Birth of Christ and Gregory of Nyssa’s Homily on the Savior’s Nativity1 and addresses the crises of his day. Proclus was bishop of Cyzicus in 430 when he proclaimed this homily in the presence of his archbishop, Nestorius, who had been installed by Theodosius II on the episcopal throne in Constantinople. The occasion, it appears, was the feast of the Virgin that had recently been instituted in Constantinople for December 26. Defying Nestorius, Proclus unequivocally defends the language of Mary as Theotokos, which for him safeguards what he calls here the “coupling of natures,” divine and human, in Christ, the “incarnate God.” To name Mary’s role in effecting this union, Proclus draws on a trove of imagery at once exuberant and focused. Mary is, following the Cappadocians, the incarnation’s “workshop,” but also a bridge, a field, and a temple.

Origen of Alexandria (ca. 185–254) was a brilliant theologian who led an instructional program under the authority of Bishop Demetrius. His reputation for learning and teaching was strong throughout the eastern Mediterranean, and he frequently embarked upon philosophical speaking tours. On one such tour Origen was ordained a priest by two Palestinian bishops, a move that, when coupled with his controversial teaching about the interrelatedness of creation and the eventual apocalyptic reunification of all rational existence (God, the angels, human souls, demons, and even the devil), spurred Bishop Demetrius to publicly censure him. Rather than subject himself to Demetrius’s episcopal rebukes, Origen relocated to Caesarea Maritima in Palestine where he would continue to teach and preach in his capacity as priest. There he would remain until his death in 253 or 254, caused by injuries he sustained under torture during the Decian persecution of 251.

Opusculum 6 is another work of Maximus that stems from his involvement in the monoenergist and monothelite controversies discussed in the introduction to Ambiguum 31 to Thomas. Opusculum 6, “Concerning the statement, ‘Father, if possible, let this cup pass from me,’” dates to 640 or 641. By that time Maximus was thoroughly embroiled in combating monothelitism. This position – which maintained that Christ had only one will (thelēma) – grew out of the somewhat vaguer and perhaps more conciliatory monoenergist position. When Heraclius promulgated the Ekthesis in 638, the deliberately nebulous language of the Psēphos gave way to a more definitive statement of the singularity of Christ’s activity and will. Maximus had already objected to monoenergism, and now all the more strongly to monothelitism. He argued that the distinction of human and divine wills in Christ did not imply their opposition, and this claim is most tested in Jesus’s prayer in Gethsemane (Matthew 26:39–40).

If Christ exists in two natures, as the Council of Chalcedon proclaims, does it follow that he performed distinct classes of activities, human and divine? If you say yes, you are a “dyoenergist” (from the Greek dyo energeiai, “two activities”); if you insist that Christ performed activities of only one class, and thus answer in the negative, you are a “monoenergist” (from the Greek for “one activity”). The dyoenergist position was defended in memorable fashion in the Synodical Letter of Sophronius of Jerusalem from the year 634. To understand this letter, as well as several documents that follow in this volume, we must set the historical context and map some difficult conceptual terrain.

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.