In the years following the death of Basil of Caesarea in 378, his younger brother Gregory of Nyssa (ca. 335–ca. 394) emerged as a leading Christian intellectual. Following his brother, Gregory wrote against Eunomius, the Pneumatomachians, and Apollinarius. He attended various synods, including the Council of Constantinople in 381. He was cited in a law of the emperor Theodosius dated July 30, 381 as one of the paragons of orthodoxy in the Eastern Roman Empire and was sent by the emperor on missions to supervise episcopal affairs as far as the province of Arabia. Dozens of his writings on various themes of Christian doctrine and practice have survived. As bishop, one of his roles was to preach at the annual feasts. The current sermon is one of the earliest pieces of evidence for a feast of the Nativity on December 25 separate from the Epiphany on January 6 – at the time this was a relatively recent distinction. We are uncertain as to which year Gregory delivered this Christmas homily, but a reasonable guess has been made that it was 386.

Soon after the deposition and excommunication of Eutyches at the Home Synod in Constantinople on November 22, 448, Bishop Leo of Rome was not only informed of the result by Emperor Theodosius II, but also received a letter from Eutyches himself, complaining of judicial impropriety and appealing to Leo to review the decision. Around the same time Bishop Flavian of Constantinople, who had presided over Eutyches’s trial, wrote a letter to Leo in which he informed him of the deposition of Eutyches and attached the minutes of the proceedings. For some reason, however, this letter did not reach Leo until May 21, 449. In the meantime, not having all the information he needed to respond to Eutyches, on February 18, 449 Leo wrote a letter to Flavian requesting a full account and asked that the minutes of the synod be sent to him. Upon receiving Flavian’s first letter on May 21, Leo quickly penned his response to the Eutychian affair and on June 13, 449 sent to Flavian the letter that would come to be known as the Tome to Flavian of Constantinople.

The Eranistes, or the Polymorphus, is Theodoret’s last extant Christological work, written in 447, shortly before the outbreak of the Eutychian controversy.1 It thus represents a statement of Theodoret’s mature Christological position. It is written in the form of dialogue between two anonymous characters, Orthodoxos and Eranistes. The main purpose of the work is to prove the real existence of both the divine and human natures in Christ after the union effected in the incarnation. It is clear from the text that Orthodoxos represents the doctrinal views of Theodoret, while Eranistes collects various “heretical” Christological opinions in his arguments – hence the name given to the imagined interlocutor, Eranistes, which in Greek means “beggar, collector.”

The Gospel of Peter is one of many non-canonical gospels produced in the early centuries of Christianity. Only a fragment is extant, containing an account of the trial, passion, death, resurrection, and ascension of Jesus. While having numerous parallels with the passion narratives in the canonical synoptic gospels, the Gospel of Peter departs from them in significant ways, such as by exonerating Pontius Pilate, by blaming Herod Antipas for the crucifixion of Jesus, and by making those soldiers who were guarding Jesus’s tomb witnesses of the resurrection. Most famously, the narrative features an enormous walking and talking cross. Scholars continue to debate whether the Gospel of Peter used one or more of the synoptic gospels as sources or was written independently of them by utilizing common sources. While the dating of the Gospel of Peter has been a heavily contested issue, the majority of scholars assign it to the years 150–190, making it one of the earliest non-canonical gospels to survive.

Gregory the Great was pope from 590 to 604. Much of what is known about his papacy comes from the collection of his letters, called the Registrum epistularum, that was assembled after his death. Over 850 of his letters survive, to a vast array of addressees on an equally vast array of subjects. Three are translated here. The first is Letter 1.24, the encyclical letter that Gregory sent in February 591 to the patriarchs of Constantinople, Alexandria, Antioch, and Jerusalem shortly after his elevation to the papacy, as a token of his communion with them. While the bulk of the letter deals with pastoral concerns, its last paragraph (translated below) contains a profession of faith meant to assure his fellow patriarchs of his orthodoxy. Here Gregory confesses his adherence to Nicaea, Constantinople, Ephesus I, Chalcedon, and Constantinople II with its condemnation of the Three Chapters.

Justin hailed from the city of Flavia Neapolis, the modern West Bank city of Nablus, in the Roman province of Syria Palestina. According to his own account in the Dialogue with Trypho the Jew, Justin became a professional philosopher of the Platonist school before adopting Christianity as the true philosophy. From his pen, we have a few surviving works: the First and Second Apologies, which some scholars believe to have been originally a single treatise, probably written in the first half of the 150s, and the Dialogue with Trypho the Jew, written perhaps around 160. He also wrote a refutation of Marcion, which has not survived. Since antiquity, the philosopher Justin who authored these texts has been identified with the Justin who was martyred in Rome, as described in the Acts of Justin. According to that text, Justin was a Christian philosopher who taught in the city of Rome for many years prior to his execution, perhaps in the middle of the 160s.

Opusculum 3 is another work that stems from Maximus’s involvement in the monoenergist and monothelite controversies. It is a fragment of a lost treatise that Maximus wrote On the Activities and the Wills, to Thalassius. Thalassius is most likely the theologian known as “Thalassius the Libyan,” who composed works of ascetic theology, including the Centuries on Theology, now included in the Philokalia. He was a leader of monks in Carthage during the reign of Heraclius (610–641). Maximus wrote several of his most important works in response to Thalassius, including his massive Questions on Sacred Scripture (ca. 633), in which he expounds on sixty-five difficult passages in scripture that Thalassius had identified. Maximus wrote On Activities and Wills in the early 640s, once he had fully entered the monothelite controversy. Only a few fragments of this treatise survive: chapter 50 (as Opusculum 2), chapter 51 (the present Opusculum 3), and some quotations in the florilegium known as Opusculum 26b.

In the late 410s or early 420s, in an epistle that is no longer extant, a monk in Gaul named Leporius, motivated by a desire to avoid attributing change and the human condition to God in the incarnation, wrote that he was disinclined to confess that God was born of a woman. Instead, he preferred to say that a perfect human being was born along with God rather than as God. The epistle sought to demonstrate this basic point and related Christological consequences through the interpretation of several key passages of scripture. But the form of Christological dualism that he advocated soon came to be deemed aberrant. When he refused to recant his views, Proculus, bishop of Marseilles, and Cillenius, a bishop of an unknown see in southern Gaul, formally rebuked Leporius in circumstances that remain unclear, and expelled him from Gaul. Along with two disciples named Domninus and Bonus, he took refuge in North Africa with Augustine.

Theodoret was born ca. 393 in Antioch to a prominent Christian family. As the only child of a devout mother, he was not only well educated in the classical sense but was also exposed to monastic spirituality and piety from an early age. While still a child he was ordained a reader in the church of Antioch. Later he moved to a monastery near Apamea (Syria Secunda), where he became a professed monk. At the age of thirty, around 423, he was elected bishop of Cyrrhus.

The long-lived Narsai – he died a nonagenarian ca. 500 – was a poet and teacher at both the School of Edessa and the School of Nisibis. His thought and works were foundational for the development of theology in the Church of the East. Steeped in Syriac literary traditions, principally the writings of Ephrem the Syrian, Narsai was also among the first generation of Syriac authors to be shaped by the theology and interpretative strategies of Theodore of Mopsuestia (d. 428) through translations of the Greek into Syriac. The work of translating Theodore’s works was centered at the School of Edessa and coincided with the fateful events around the Council of Chalcedon and the resulting strife surrounding the Christological debates. Narsai’s poetry displays his dynamic reception of both Ephrem and Theodore’s theological and interpretative programs. Working in the aftermath of Council of Ephesus, Narsai became embroiled in the Christological controversies, often reflected in his poetry. At an uncertain date prior to the closure of the School of Edessa in 489, Narsai and his colleagues departed from Edessa, leading to the formation of the School of Nisibis within the Persian Empire.

Tertullian wrote Against Praxeas in the early 210s. It is thus a product of the latest part of his career, when he had become a vocal supporter of what he called the New Prophecy. This was a controversial, revivalist movement, termed Montanism by its opponents, which owed its origins to the region of Phrygia in Asia Minor. There, in the late 150s, a new convert to Christianity named Montanus began making prophecies about the coming end of days, and the consequent need for Christians to follow a more rigorous code of behavior. Other prophets followed him, including two women named Prisca and Maximilla. As Against Praxeas makes clear, the followers of Montanus placed great significance on the Paraclete (“Advocate” or “Helper” in Greek), who is identified with the Holy Spirit in the Gospel of John (see especially 14:26). Tertullian says that the Paraclete had provided him with new insight into the relation between God and Christ, thus suggesting that his account of the Father and Son was closely linked with the New Prophecy of Montanism, which was subsequently dismissed as heretical.

In what follows, the fifth-century Syriac writer Narsai considers several moments from biblical stories in order to understand their significance for how Christians should think about Christ. Each of the vignettes Narsai discusses – the creation of humanity, an angel’s visit to Mary to announce her pregnancy, Jesus’s circumcision, and his baptism by John – offers a way to consider the purpose and nature of Christ as the Word of God. Throughout Narsai affirms the immutability of the Word even in the incarnation and stresses that it was the human being who was the subject of these biblical events, not the immutable Word of God. Narsai holds that the immutable Word did not literally became flesh in the incarnation (since that would be impossible for the Word), but rather indwelt the human being for the purpose of revealing knowledge of God. Narsai’s ideas about these situations and others frequently reflect the teachings of Theodore of Mopsuestia, a writer and church leader who died in 428 and whom Narsai revered. That said, his ideas also go beyond Theodore’s teachings, and show us the development of Christian thought about Christ from one generation to another.