Ludwig Heinrich von Jakob claims in his 1788 “On Freedom” that we know we are free by virtue of our self-consciousness. Drawing broadly on Kant’s doctrine of the fact of reason, Jakob asserts that freedom is a fact. However, Jakob does not claim that this fact is furnished by consciousness of the moral law. Instead it is immediately given through inner sense. This supposedly parallels how we know that a body is distinct from us because our consciousness of it as given through outer sense entails that it does not belong to our self.

Ephrem the Syrian is one of the two most important fourth-century Syriac writers.1 He was born ca. 307–309 in the Roman city of Nisibis (modern-day Nusaybin in Turkey) and was likely raised as a Christian, having close relationships with the city’s bishops from his youth. He was a member of the îḥîdāyê (“single ones”), a group within the larger Christian community whose members devoted themselves to asceticism and celibacy without forming a distinct monastic community. This was a pattern of Christian living that was peculiar to Syriac-speaking regions. Ephrem also served his community as a teacher and perhaps also as a deacon. Above all, Ephrem was a writer: he wrote in multiple genres, including biblical commentaries and metrical homilies (memre), but he is especially known for his hymns (madrāse), about 400 of which are extant. In 363 Ephrem relocated to Edessa (modern-day Urfa in Turkey) when Nisibis, on the border between the Roman and Persian Empires, was ceded by the Romans to the Persians, prompting Christians to emigrate.

We first learn of Irenaeus in a letter he carried to Eleutherius, bishop of Rome, from the churches of Vienne and Lyons which were seeking a peaceful resolution to the Montanist controversy.1 The letter introduced Irenaeus as an esteemed presbyter in their community. By the time Irenaeus returned from his embassy a severe persecution (ca. 177 CE) of the churches in Vienne and Lyons had claimed the lives of many, including that of Pothinus, the aged bishop of Lyons. Irenaeus was installed as his successor.

Tertullian’s On the Flesh of Christ offers a defense of the reality of Christ’s human body and the sufferings that he experienced during his time on earth. The work, written around 206, roughly in the middle of Tertullian’s literary career, was directed against alternative views prevailing among some Christian groups concerning the body of Christ. The Christians who held these views are now called docetists. They believed that Christ only seemed to have a human body, and that his sufferings and death were consequently not real. Tertullian’s attack on the docetic perspective targets three influential figures of the second century who had questioned the reality of Christ’s body in different ways. The first of these is Marcion, treated in chapters 2–5, who denied the reality of Christ’s birth and flesh. Second is Marcion’s disciple Apelles, treated in chapters 6–9, who believed that Christ did have flesh during his time on earth, but that he had not really been born. Finally, in chapters 11–16, Tertullian addresses the views of Valentinus and his followers, who granted the reality of Christ’s birth and body, but suggested that his flesh was not human.

A number of letters of Timothy Aelurus survive in Syriac. These reveal Timothy in a more pastoral and less polemical light, as these letters are generally written to support miaphysites throughout the Roman Empire in the midst of not only their struggles to maintain their faith but also their challenges in creating a miaphysite church. One such letter was written to Claudianus. Identified as an abbot and priest, nothing more is known about him. The heading of letter (which is not part of the original letter) claims that it was written in exile from Chersonesus. If that is correct, then is dated to 464/5–475. Toward the end of the letter Timothy mentions a small treatise he wrote when summoned by the emperor (presumably to Constantinople). If this happened under Emperor Leo, it supports the dating of 464/5–475. But such a summons is otherwise unattested. If the summoning refers to when Emperor Basiliscus called Timothy to Constantinople in 475, the letter must have actually been written after his exile in Chersonesus and thus must be one of his last extant works before his death in 477. No other evidence helps to decide the issue.

Hilary of Poitiers was one of the premier theologians of the Latin West in the fourth century, along with Ambrose of Milan and Augustine of Hippo. In 356 he was banished at a synod at Béziers for his support of Athanasius and the Alexandrian bishop’s “anti-Arian” program, and exiled to Asia Minor for four years. Here Hilary became far more knowledgeable about the theological debates rocking the church, and his own theology was decisively shaped by the encounter. He was particularly influenced by the Homoiousian theology of Basil of Ancyra. Hilary attended the Council of Seleucia in 359, which promulgated a broadly Homoian creed that was given official approval, under the auspices of Emperor Constantius, at Constantinople in January 360. During his exile in the East he penned a number of theological works, including On the Trinity, against Homoian theology. Shortly after the synod in Constantinople he returned to his homeland, where he worked against those who supported Homoian theology. He died in 367 or 368.

Here Gregory of Nazianzus fulfills his promise made at the end of his Letter 101 to Cledonius to “compose psalms, write many words, and give them meter.”1 Indeed, if Gregory’s longest argument against Apollinarius’s Christology comes in Letter 101, his most laconic one comes in these didactic verses, Poems 1.1.10–11. These texts, like Letter 101, reveal one of the most idiosyncratic features of his Christology, that Gregory takes heterodox Christologies as a personal affront; to deny that Christ had a mind, as he polemically frames Apollinarius’s position, is to deny Gregory’s mind access to salvation, and thus Gregory responded with aggressive polemic.2 This gives Gregory’s argumentation a special tenor relative to later, more technical discussions of Christology. Unfortunately, modern critical editions of Poems 1.1.10 and 1.10.11 do not exist; this translation is based on the Benedictine text contained in PG 37: 464–471.

Emperor Justinian convened the second Council of Constantinople in 553 for the sole purpose of condemning the so-called Three Chapters – the person and writings of Theodore of Mopsuestia (d. 428), certain writings of Theodoret of Cyrrhus (d. ca. 466), and the Letter to Mari the Persian attributed to Ibas of Edessa (d. 457). Why was it deemed expedient to condemn these figures and their writings a century after their deaths? The reasons are complicated and remain debated by scholars. Justinian was at least partially motivated by fostering a reconciliation of anti-Chalcedonians with the imperial, Chalcedonian church. The condemnation of the Three Chapters by a joint council of Eastern and Western bishops was probably intended to demonstrate to anti-Chalcedonians that the charge of “Nestorianism” they leveled against the imperial church was groundless.

Athanasius was bishop of Alexandria on and off for nearly fifty years, from his contested election in 328 until his death in 373. He is perhaps best known for the unflinching promotion of a theology which he claimed represented the traditional Christian viewpoints articulated at the Council of Nicaea, against Trinitarian heterodoxies he connected with Arius and those supposedly influenced by him. Various emperors irked by his ecclesio-political efforts deposed Athanasius from his see no less than five times, causing him to spend many years in exile. Though Athanasius is most famous for his defense of the Nicene doctrine of the Trinity, Christological concerns were never far from his mind and some works of his, or at least sections thereof, are even specifically Christological in focus. For example, On the Incarnation (composed ca. 328–335) is a meditation on the person of Christ and soteriology, arguing that the salvation of humanity could only be achieved through the fully divine Word becoming incarnate, whereas his Oration against the Arians 3.26–58 (early 340s) defends the reality of the incarnation of the Word against “Arian” scriptural arguments against it.

Among other things Basil of Caesarea was renowned for his preaching.1 Both as a presbyter and then a bishop, he preached on a regular basis on the various Sundays, feasts, and celebrations of the church’s liturgical calendar, as well as at synods and other ecclesiastical gatherings. Only about fifty of his homilies are extant, one of which is his Homily on the Holy Birth of Christ. Some scholars claim it is one of the earliest witnesses to the celebration of Christmas on December 25, but if not, it was probably preached on January 6 in celebration of the feast of the Theophany (also known as Epiphany). The year cannot be determined with any precision, but Basil probably delivered it during his episcopacy, 370–378, which is roughly the same period in which Letters 261 and 262 were written.

Maximus (579/80–662) is one of the most important and influential theologians of the seventh century. His numerous works delve into Trinitarian and Christological theology, metaphysics, anthropology, ascetic spirituality, and an all-embracing vision of cosmic transformation and transfiguration centred on the person of Christ. While the texts translated in this volume are primarily Christological, Maximus’s thought is not easily compartmentalized, and his reflections on the person, natures, activities, and wills of Christ are bound up with his commitment to the authority of scripture and the fathers, to philosophical rigor, and especially to salvation as deification.

In the years after the second Council of Constantinople in 553, both pro- and anti-Chalcedonians had occasionally spoken of Christ having a single activity (energeia), language which had some precedent in authors regarded as authoritative by both factions. But the validity of this so-called monoenergist doctrine was still very much a live issue on which there was no consensus in either pro- or anti-Chalcedonian circles. In the 610s, however, Sergius of Constantinople (patriarch 610–638) began to promote the doctrine of monoenergism in the name of Emperor Heraclius (r. 610–641) not only as a possible basis for reconciliation between the imperial church and miaphysite anti-Chalcedonians, but also as a legitimate clarification of Neo-Chalcedonian Christology. The apogee of imperially backed monoenergism came in 633 when on its basis Cyrus the Chalcedonian patriarch of Alexandria reached an accord with Egyptian miaphysites, an agreement memorialized in the Plerophoria, also known as the Pact of Union.

All that survives of the epistolary corpus of Apollinarius of Laodicea (ca. 315–392) are four intact letters and fragments of four others.1 What is probably the earliest Christological statement we have from Apollinarius is found in his Letter to Emperor Jovian, also called The Profession of Faith to Emperor Jovian, a letter to the new (pro-Nicene) emperor Jovian, who ascended to the throne in June 363 and ruled until his death in February 364. This letter might simply be an introductory statement of faith to a new emperor, which other bishops generally saw as unavoidable formalities to be completed without making waves. Indeed, Athanasius’s letter to Jovian (Ep. 56) simply repeated the Nicene Creed with little interpolation or interpretation. However, the fact that Apollinarius took the exercise as an opportunity to submit his Christological thought for imperial consideration might suggest a different context, perhaps that he was offering the new emperor a way forward in the efforts to reconcile the Christian factions in Antioch (Eustathians, Meletians, “Arians” of various stripes) by highlighting his own position.

Babai the Great (d. 628) was the most important author of his generation in the Church of the East (also called the East Syrian or “Nestorian” church), the largest Christian community in the Sasanian empire. A monastic reformer, hagiographer, and theologian, he championed the doctrine that came to define his church’s orthodoxy – that Christ is two natures (kyāne) and two hypostases (qnome), united in one person (parṣopā). On the Union, selections of which are translated here, was Babai’s most thorough exposition of this teaching.

The Formula of Reunion in 433 officially restored the peace of the churches but did not bring the Christological debate to an end.1 The resolution had been achieved only through delicate and difficult negotiations, and further diplomacy was required to maintain the fragile peace. The leaders of each party had the unenviable task of selling the agreement to their followers, some of whom were disinclined to accept any agreement with the opposing side. Some of the Easterners (so called because they came from the Roman diocese of Oriens or “East”), such as Theodoret, insisted that Cyril’s signing of the Formula of Reunion could only be interpreted as a departure from the position he had maintained earlier in the controversy, and they began pressing Cyril’s supporters with hard questions on this point. Cyril’s partisans then turned to the Alexandrian bishop to ask him to weigh in on the matter. On such person was Succensus, bishop of Diocaesarea in the province of Isauria, to whom Cyril penned two letters addressing the questions being posed by the Easterners and debated amongst his own followers.

The date of this text written by Apollinarius of Laodicea (ca. 315–392) is difficult to determine with specificity.1 It should simply be placed in the late 360s or 370s. Here Apollinarius demonstrates the union between divinity and flesh in Christ. He employs the Greek term hypostasis to express the basic union between Christ’s flesh and divinity. Perhaps more radically than he does in On the Body’s Union with the Divinity in Christ,2 Apollinarius now applies “same-in-substance” (homoousios) to Christ’s flesh. This text, once attributed falsely to Julian of Rome, does not fully survive in Greek.

Emperor Justinian reigned from 527 to 565, but had already played a decisive role in the reign of his uncle and predecessor Justin I (r. 518–527). Before Justin, imperial policy in Christological matters was officially dictated by the Henotikon that had been issued in 482 to reconcile pro- and anti-Chalcedonian factions within the church. Written by the patriarch Acacius of Constantinople and promulgated by Emperor Zeno, this document embraced a studied ambiguity by avoiding technical terminology in minimalist Christological formulations, by giving approval to both aspects of Cyril’s theology (represented by the strongly miaphysite Twelve Chapters and the dyophysite-leaning Letter of Reunion to John of Antioch), and by reducing the council’s work to the condemnation of Nestorius and Eutyches in order to undermine the achievement of the Chalcedonian Definition. Western bishops, who held Chalcedon in high regard, rejected the Henotikon outright, leading the bishop of Rome to break off communion with Acacius, resulting in the so-called Acacian Schism.