The Teaching of the Twelve Apostles, also known by the first word of its Greek title, the Didache, is a very ancient text, most likely contemporary with some of the books later included in the New Testament. Scholars typically date it to the latter half of the first century or the first half of the second century. Its author and place of origin are unknown, though some scholars associate it with Syria. The text, as we have it, is the end result of a complex process of redaction. Initially, the document was likely a compilation of various traditional sources deemed useful to introducing converts to a Jewish-Christian community’s way of life, which was then altered and expanded over time as community standards changed and developed. Its first part (1–6) is a prebaptismal catechesis composed of moral precepts derived from an independent and preexisting Jewish source known as the “Two Ways.” Its second (7–10) and third (11–15) parts are a collection of liturgical and disciplinary rules for the developing Christian community concerning baptism, fasting, prayer, the communal meal, traveling apostles, prophets, teachers, hospitality, reconciliation, communal leadership, and fraternal correction. The final part (15–16), whose ending is lost, describes the eschatological expectation that early Christians held.

Here is another text that witnesses to the early period of the island monastery of Lérins. Its author, Faustus, succeeded Maximus twice, first as abbot of Lérins and then as bishop of Riez. For his part, Maximus became the abbot after the monastery’s founder, Honoratus, was appointed bishop of Arles in 427 or 428. Maximus served as abbot until 433 or 434, when he became bishop of Riez. Faustus then replaced Maximus as abbot of Lérins, and when Maximus died sometime between 457 and 461, Faustus replaced him again, this time as bishop of Riez. Shortly after Maximus’ death, Faustus preached a homily to the church of Riez that stressed how the monastic virtues Maximus acquired at Lérins were a providential training for his pastoral ministry as bishop of Riez. In fact, Maximus was but one of several Lérinian monks installed as bishops in the 420s and 430s: besides Honoratus becoming bishop of Arles, also Hilary was made bishop of Arles in 430 and Eucherius bishop of Lyons around 434. Of course, Faustus himself followed the same trajectory.

Augustine was plunged into the Donatist controversy upon becoming bishop of Hippo in 395. In the wake of the Diocletianic persecutions in the early fourth century, the Donatists had split from the group whom Augustine called and considered “catholics” (i.e., “worldwide Christians”), creating a schism in the North African church that lasted for well over a century. The very nature of the church was in dispute: Donatists believed that the church must retain its purity and holiness, separating itself from sinners, whereas catholics maintained that the church could tolerate the presence of sinners as long as consent was not given to their sin. Donatists believed that catholics were implicated in the sin of those who lapsed in the Diocletianic persecutions by handing over the scriptures to imperial authorities; they believed that only by retaining its purity in this way could the church guard against catholic contagion. Furthermore, they regarded any sacrament administered by a cleric in a state of sin as invalid, and accordingly former catholics entering their communion had to be baptized (for the first time, in their view).

Among his many duties as bishop of Hippo in North Africa, Augustine (354–430) oversaw the reception of converts into the church. When newcomers to Christianity were ready to prepare for baptism, they were designated as catechumens. The catechumenate was a period of training, often lasting several years, in which newcomers learned how to live as Christians. At the beginning of each Lent, those catechumens who wished to be baptized at the upcoming Easter would submit their names and thereby formally become “petitioners” (competentes). During Lent the petitioners engaged in a number of ascetical and ritual practices designed to complete their initiation into the Christian way of life. These included fasting, undergoing periodic exorcisms, and receiving special instruction from the bishop by listening to sermons that covered a broad range of Christian doctrine and practice. Two weeks before Easter, petitioners participated in a ceremony known as the traditio symboli, the “handing over” of the creed. At this ceremony the bishop formally recited the creed, with the expectation that afterward the petitioners would memorize it. There was a similar ceremony that “handed over” the Lord’s prayer (traditio orationis). At the Easter Vigil, the petitioners would “hand back” the creed (redditio symboli) and the Lord’s prayer (redditio orationis) by reciting them before the congregation and fully participate in the Eucharistic liturgy for the first time, in the course of which they received the sacraments of initiation: baptism, chrismation, and Eucharist. During the Easter octave – the eight days from Easter Sunday to the following Sunday, counting inclusively – the newly baptized, whom Augustine called “newborns,” would attend sermons that unpacked the meaning of the sacraments they had just experienced and received at the Easter Vigil.

Thascius Caecilianus Cyprianus – better known to history as Cyprian – converted to Christianity around 246 after a successful secular career as a rhetorician. Soon he was ordained to the priesthood and in 248 or 249 was consecrated as the bishop of Carthage. Not long after this, in late 249, the persecution of Emperor Decius broke out and Cyprian fled Carthage out of a concern that his church not be deprived of its bishop, as had recently happened in Rome and elsewhere. When the persecution ended in 251, in its wake there arose in Carthage and Rome several theological and pastoral problems, particularly over the readmission into the church of those who had lapsed in the persecution. Cyprian adopted a measured policy of readmitting the lapsed after a period of suitable repentance, and this policy was adopted also by Cornelius, the new bishop of Rome. He lays out this approach in On the Lapsed (De lapsis), written in 251. But laxists in Carthage, who supported the lenient readmission of the lapsed, and rigorists in Rome, who denied that readmission was even permissible, opposed the official policy, leading to schisms in both places.

As noted in the introduction to Hilary’s Sermon, Honoratus founded a monastic community sometime between 400 and 410 on an island off the coast of what is now Cannes in southern France. Then called Lerina, the island is now called Île Saint-Honorat de Lérins. Inspired by the desert fathers he had visited during his travels, Honoratus initiated at Lérins a style of monastic living that stressed individual ascetic pursuits within a communal context. It has been described as a monastery of hermits in community. As time went on, however, and due to the influence of the writings of Augustine and John Cassian – the latter dedicated his second set of Conferences to Honoratus and Eucherius (another monk of Lérins, who was chosen bishop of Lyon around 434) – the monastery of Lérins came to place more emphasis on the communal aspects of monastic living.

Between 400 and 410, Honoratus, the scion of a noble Gallic family, founded a monastic community on the island of Lérins (modern Île Saint-Honorat de Lérins, just off the coast of Cannes in southern France). A charismatic figure, Honoratus inspired many men from Gaul and elsewhere, including his relative Hilary, to take up the ascetic life at Lérins. Some years later, around 427 or 428, when the island monastery had become an unqualified success, Honoratus left to become bishop of Arles, although he died shortly thereafter in 430. His successor as bishop, Hilary, commemorated the first anniversary of Honoratus’ death in 431 with a sermon delivered to the Christian community of Arles on his life and virtues. Having only been in office for a year, Hilary used the sermon to provide a kind of apologia for his own episcopal leadership, presenting himself as Honoratus’ handpicked and personally trained successor. Hilary served as the bishop of Arles until his own death in 449.

Caesarius was born in the Burgundian city of Chalons-sur-Saône around 470. At the age of seventeen, he entered the island monastery of Lérins. But after a few years he was sent to Arles to regain his health, which he had ruined through intense asceticism. Aeonius, the bishop of Arles and a relative of Caesarius, ordained him to the diaconate and the priesthood, then appointed him the abbot of Trinquetaille, a monastery in the suburbs of Arles. When Aeonius died in 501 or 502, Caesarius succeeded him as bishop, a position that embroiled Caesarius in the politics of the area, in which the interests of the Visigoths, the Franks, and the Gallo-Romans were often in conflict. He became the most prominent bishop in the Gallic church when pope Symmachus of Rome confirmed him as metropolitan and papal vicar for Gaul in 514. He presided over a number of synods and councils in Gaul, the most important being the Council of Orange in 529, which condemned the teaching on grace that predominated in southern Gaul in favor of a modified Augustinian position.

In his autobiographical Confessions, Augustine (354–430) recounted his own circuitous path to Christianity. When he later became bishop of Hippo in North Africa, Augustine oversaw the reception of converts into the church. So Augustine was intimately aware of dynamics of conversion and the many forms it could take from both personal and pastoral experience. In Sermon 279, which was preached in Carthage on Sunday, June 23, 401, Augustine touches upon several facets of conversion to Christianity.

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.

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.

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.

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.

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.

Ignatius, bishop of Antioch in Syria, penned seven letters while being escorted under guard to Rome for execution during the reign of Trajan (98–117 CE). No explicit evidence confirms that he reached the imperial capital, but there is no reason to doubt the tradition that he was martyred there. These letters illuminate numerous aspects of early Christian life and thought, providing as well insight into their author’s concerns. Since the seventeenth century these letters have been included in the collection of early Christian writings known as the Apostolic Fathers. Three matters above all repeatedly surface in these letters: (1) Ignatius’s struggle against those whose teaching differed from his own; (2) his pleas for the unity of the church by communion with and obedience to the bishop; and (3) his own suffering and impending death and their meaning, which he interprets in Christological categories.