The expansion of Christianity in this period was rapid and far-flung. It penetrated Mesopotamia to Edessa and Arbela and reached as far west as the interior of Spain, and perhaps the southern coast of Britain. Christians were to be found on the Rhone in Gaul, and even on the Rhine. The Dalmatian coast was beginning to be missionized. The Church was taking root in North Africa, Cyrenaica, and interior Egypt, as well as consolidating and enlarging its gains in Syria, Greece, Asia Minor, and Italy. The spread of the new faith naturally followed the great trade routes and was centered in the cities. Only gradually did it win the rural areas, where ancient traditions were more stubbornly defended.
Primary among the marks of the period is the rise of the Catholic consciousness. By this phrase is meant the emergence of a distinctly ecclesiastical point of view, evident in the ordering of Church life. The kerygma, or "preaching," of the New Testament becomes the regula fidei of the early Fathers. Didactic and ethical interests come to the fore. The faith is more carefully prescribed and the Church more exactly organized. The leading concern is to conserve the apostolic witness, and, while showing its relevance to pagan modes of thought, to guard against the extremes of Gnostic speculation and prophetic enthusiasm.
Under the single bishop who, with his council of presbyters, rules the congregation, there is built up a closely knit organization which will be able to withstand the concerted persecutions of the third century. The bishop is the successor of the apostles, representing the localizing of the prophetic, teaching, and liturgical functions of the original apostolate. He becomes the center of the Church's life, the living witness and guardian of its faith. Exactly how it came about that a single bishop should succeed to powers earlier vested in local bodies of presbyters, is not altogether clear; though much may be explained by the occasional settling of an apostle, prophet, or teacher of the original missionary ministry, in some locality. What, however, is clear is that the development was orderly, and that it was very widespread by the time of Ignatius. The obvious convenience of having a single administrative head, the economic necessity whereby a congregation could afford to maintain only one full-time official, the dominance of certain leading personalities, together with the suitability of having a single celebrant for worship -- all these factors doubtless played a role in the rise of the monepiscopate. It is, indeed, already foreshadowed in the Pastoral Epistles, where Timothy and Titus are viewed as Paul's delegates, entrusted with the supervision of the presbyteries in Ephesus and Crete. The final step is taken in the communities reflected in Ignatius' correspondence. There the bishop is the bishop of a local congregation, and the term, originally synonymous with "presbyter," now characterizes this distinctive office.
The bishop is the living center of the Christian tradition. He is a prophetic as well as a sacramental person; and nothing more clearly reveals the second century attitude toward the episcopate than the description the Smyrnaeans give of their martyred bishop, Polycarp: he was "an apostolic and prophetic teacher" (Mart. Poly.16:2).
With the rise of the episcopate there emerges the importance of the great sees of Christendom, claiming apostolic foundation. The significance of the episcopate in Irenaeus, for instance, does not lie in a sacramental chain of ordinations, but in a chain of authorized teachers, which reaches back to the apostles. Of first importance among such sees is Rome, the center of Western Christianity, whose place of eminence is due both to its being the imperial city and to its being the city of Peter and Paul. It is, too, Christendom in miniature, for there Christians from all lands eventually turn up. In consequence, Rome is the ideal center from which to set one's compass of orthodoxy.
The tradition of the faith, however, was incorporated in more than living personalities. It was enshrined in a book, and expressed in brief, formal statements suitable for baptismal confessions. The second century saw the rise of the New Testament canon and the formation of the earliest creeds. Both were partly determined by the pressure of heresy and the consequent necessity for the Church to make its message clear. But heresy was only one factor in the development. The internal needs of the Church were such that the tradition should be preserved in accepted writings and in authentic confessions.
The New Testament canon has its origin in the high regard with which Christians from the first viewed the logia of the Lord and the writings of apostles. Until A.D.150, however, the only Bible of Christians was the Septuagint, the Greek Old Testament. This the Church had inherited from Judaism, and at first it sufficed. The Christian message entailed the explication of the Old Testament in the light of the acts and words of the Messiah. What was foreshadowed in the sacred books of the Law and the Prophets had now come to pass in the Christ. Hence Christian preaching was founded on the Old Testament and on the living tradition of Jesus, passed from mouth to mouth. This feeling for personal witness was very strong in the Early Church. Papias, for instance, records his disdain for books and his preference for "the living and abiding voice." The tradition was not something dead, but a vital reality to be discovered from living persons. Yet the corruptions to which oral tradition was subject soon necessitated the writing of Christian books; and as the living witnesses to Christ and the apostles passed away, these books took on a new significance. They came to be read in worship, and by A.D.150 they had gained the authority that had once belonged exclusively to the Old Testament.
The actual formation of the canon, however, was both determined and hastened by the Gnostic rejection of the Old Testament. The sharp dualism of the Gnostics, who viewed the Jewish and Christian revelations as antithetical, found its clearest expression in Marcion, who flourished in the middle of the second century. He contrasted the good God revealed in Jesus Christ with the Old Testament God of retaliation and vengeance, whom he viewed as responsible for the evil in creation. In consequence, he did away with the Old Testament as the sacred book of Christians, and in its place he supplied a canon called "The Gospel and the Apostle." The "Gospel" was a form of our present Luke; the "Apostle" was a corpus of ten letters of Paul. Both the Gospel and Paul he expurgated of Old Testament references, to suit his theology. The Catholic canon was doubtless framed with Marcion's in view, though it was not until the fourth century that there was final unanimity on which books should be included. Three of the works in our present volume (I Clement, II Clement, and the Didache) were at one time part of the New Testament in some areas of the Church.
The creed developed as a baptismal formula. The most important is the Roman symbol which underwent various revisions until the seventh century, and came finally to be known as "The Apostles' Creed." Its primitive form is reflected in Irenaeus, and at the end of the second century Hippolytus  gives us the first text of the three statements to which the baptized yielded assent on their immersion.
The process whereby the faith became ordered in the episcopate, preserved in the canon, and defined in a creed, has its counterpart in the development of the liturgy. Throughout the second century prayer was still extemporaneous, though set forms and phrases had been taken over from the Jewish synagogue, and Christian prayers were gradually becoming stereotyped. We have an instance of a traditional intercessory prayer in I Clement (chs.59 to 61), and some reflections of the Eucharistic prayer will be observed in Polycarp's Martyrdom (ch.14). The primitive prayers of the Didache survived in Alexandria, and, indeed, turn up two centuries later in Egyptian liturgies. But it was the structure, rather than the exact wording of the liturgy, that was early established. The way in which the Church should continue the action of Jesus at the Last Supper was a matter of grave importance. It was an action that was the center of the Church's life, for by this mystery the Christian believed he was incorporated into the very humanity of Christ (Justin, Apol. I, ch.66).
By the turn of the first century the Eucharist was no longer a supper meal. The ceremony of the bread and wine had been attached to a service of lections and prayer, derived from the synagogue. The first description we have is in Justin's Apology (I, chs.65; 67). The service takes place about dawn in a private house, and its order is as follows: lections, sermon, intercessory prayers, kiss of peace, offering of the bread and wine, consecration prayer, Communion. By the end of the century we have a text of the consecration prayer in Hippolytus, though that learned Roman is careful to indicate that he is giving a pattern, not insisting on the exact words to be followed. 
The change from a supper meal to a dawn service arose from several factors. For one thing, slaves, who formed a significant part of a Christian congregation, were not free to attend an evening meal. Then again, imperial edicts had forbidden unlicensed clubs to hold such suppers. Moreover, to Gentiles, who dated their days from midnight, a supper on Saturday evening would have seemed an odd way of celebrating the day of the resurrection. Jews dated their days from sundown, and so the primitive Christian communities (envisaged in the liturgical section of the Didache) naturally celebrated the day of the resurrection with a Saturday supper. For Gentiles, however, this cannot but have seemed inappropriate.
Practically all the documents in our volume refer to the persecution of Christians, and of this a brief word may be said. It is a disputed point whether Christians in this early period were persecuted because of an official, imperial rescript forbidding their existence, or whether the action taken against them rested only on the general police powers of Roman magistrates. In any case there was persecution; but it was neither so incessant nor so widespread as is often imagined. There were spasmodic outbreaks of a savage nature, as Nero's action, or the condemnations of Ignatius and Polycarp, or the sad tale of the martyrs in Lyons and Vienne. But the State made no concerted attempt to stamp out Christianity until the days of Decius in the middle of the third century. Yet by their attacks on the Roman gods and by their refusal to sacrifice to the imperial genius, the Christians were always liable both to popular vengeance and to criminal prosecution.
Internally, the life of the Church in the second century was disturbed by two important movements -- Gnosticism and Montanism. The former was an attempt to modernize the faith by accommodating it to the syncretic spirit of the age. During our period the type of Christianity that flourished in two widely separated centers, Edessa and Alexandria, was avowedly Gnostic; and not, indeed, until the turn of the second century did there emerge significant Catholic minorities in those areas.
Gnosticism  is older than Christianity. It represents the fusion of Oriental and Greek ideas into various elaborate systems whose aim is to acquire "gnosis" or knowledge of the divine. Ancient mythological material is blended with philosophic and religious ideas. Sometimes the dominating interest is the philosophic one-the problem of the one and the many. At other times the religious element is primary, and salvation is sought from the insecurity and evil of the natural world. Popular magical notions and astrology also enter in; and the vast movement of Gnosis had manifold forms throughout the Hellenistic world. Gnosis is knowledge based on revelation, but it is not intellectual knowledge. It is saving knowledge, enabling the soul to escape from the flux and change of life and to find the assurance of immortality. By the true gnosis the soul is freed from the evil prison house of the body into which it has fallen, and empowered to ascend to its original home in the spiritual world.
In the Christian forms of Gnosis there are instances where the Christian element is clearly a superficial addition to a system already complete. But in other cases, as in those of the great Alexandrine teachers, Basilides and Valentinus, the Christian factor is fundamental. Yet all Gnostic systems depend upon a principle that is at variance with Christianity -- the dualism of matter and spirit. That the body was basically evil, and in no sense the creation of a good God, was a central tenet. It led Gnostics to dispute the underlying message of the Old Testament, and to contrast the creator-God with the God revealed in Jesus Christ. In consequence, as we have already seen, the Old Testament was rejected, and new Christian books were substituted in its place. It is interesting that not only the first New Testament canon comes from Gnostic sources, but Gnostics were the first to give New Testament passages the authority once enjoyed by the Old Testament ( Basilides), to write a New Testament commentary ( Heracleon), and to make a Gospel harmony ( Tatian). This peculiar interest in a New Testament stems from the rejection of the Old.
Other serious consequences followed from the Gnostic disparagement of the body. The doctrine of the incarnation was denied. Jesus only "appeared": he did not genuinely take on human flesh. Hence these Gnostics came to be known as "Docetics" (from dokeO, appear); and it is against this aspect of their teaching that Ignatius' letters are primarily aimed.
In the ethical sphere the Gnostics either espoused a strict asceticism or else indulged in antinomianism. In the one case they argued that the soul should cut itself as loose as possible from the material world; in the other case they contended that, because creation was outside the sphere of the good God, the soul's relation to it was a matter of indifference. Both these attitudes were challenged by the anti-Gnostic writers, such as Irenaeus; while it is against the second that the earliest Christian sermon (II Clement) is directed.
At the opposite pole to Gnosticism stands the Montanist movement of the latter half of the second century. In essence this was an earnest attempt to recover the prophetic note in primitive Christianity, and to challenge both the intellectualistic tendencies in Gnosticism and the ecclesiastical trend of the second century Church. It was a revival of the religion of the Spirit -- an ecstatic outburst, eagerly expectant of the end of the world and rigorous in its ascetic demands. It opposed the developing laxity in Christian morals, which went hand in hand with the Church's claim to forgive sins after baptism, and the antinomianism to which some forms of Gnosticism had led. Born in Phrygia in Asia Minor, it passed eventually to North Africa, where it won for its cause the vehement Tertullian, in whose writings it takes on a severely puritanical note. But its most characteristic feature was its revival of prophecy and its emphasis on the Spirit. Wrapped in ecstatic visions, Montanus and his prophetesses declared new revelations, foretelling the coming of the New Jerusalem, forbidding second marriages and second repentance, and insisting on rigorous fasts and other ascetic practices.
The Catholic opposition to Montanism rested on the conviction that the Christian revelation was complete. Nothing new in principle could be added to the apostolic deposit of the faith. The Church, too, was cautious about ecstasies in which the prophet lost the use of his reason and identified himself with God. "I am come neither as an angel, nor as an ambassador, but as God the Father," said Montanus. Against such extravagant claims, the Church insisted on the sufficiency of the apostolic tradition.
The ascetic tendencies in Gnosticism and Montanism affected the ethical life of the Catholic Church. While the extremes of both positions were renounced, an increasing veneration of celibacy and virginity is to be observed. In both Justin and Athenagoras this is apparent; and it reaches its full expression in the development of monasticism in the fourth century.
To conclude: The dominant interest of the second century Church was the ordering of its life and teaching. To preserve the apostolic witness against Gnostic perversions and Montanist extravagancies, the episcopate, the canon, and the creed were developed. To interpret it to the Gentile mind, its affinities with the best in pagan religious thought were utilized. To maintain it against persecution, the martyr was willing to suffer. Finally, to ensure the perpetuity of the faith, the Church built up a closely knit organization which was as uncompromising toward heresy and schism as it was toward the demands of the State.
 Apostolic Tradition, ch. 21. For the early dating of this work, see my article in the Anglican Theological Review, January, 1948, pp. 38-44.  Apostolic Tradition, chs. 4; 10:4.  For a clear and cogent survey of Gnosticism, with some reference to the recent discoveries in Egypt, see G. Quispel, Gnosis als Weltreligion. Origo Verlag, Zurich, 1951.
 Apostolic Tradition, chs. 4; 10:4.
 For a clear and cogent survey of Gnosticism, with some reference to the recent discoveries in Egypt, see G. Quispel, Gnosis als Weltreligion. Origo Verlag, Zurich, 1951.