But it did not win its victory without a struggle. Superstition, misunderstanding and hatred caused the Christians trouble for many generations, and governmental repression they had to suffer occasionally, as a result of popular disturbances. No systematic effort was made by the imperial authorities to put an end to the movement until the reign of Decius (250-251), whose policy of suppression was followed by Diocletian (303 ff.) and continued for some years after his abdication. In spite of all opposition the Church steadily grew, until in 311 the emperor Galerius upon his death-bed granted toleration (see Eusebius H.E. x.4, and Lactantius, De mortibus persecutorum, 34), and in 313 the emperors Constantine and Licinius published the edict of Milan, proclaiming the principle of complete religious liberty, and making Christianity a legal religion in the full sense (see Eusebius x. 5, and Lactantius 48. Seeck, Zeitschrift für Kirchengeschichte, xii. 381 sq., has attempted to show that the edict of Milan had no significance, but without success).
Constantine, recognizing the growing strength of the Church and wishing to enlist the loyal support of the Christians, treated them with increasing favour, and finally was baptized upon his death-bed (337). Under his successors, except during the brief reign of Julian (361-363), when the effort was made to reinstate paganism in its former place of supremacy, the Church received growing support, until, under Theodosius the Great (379-395), orthodox Christianity, which stood upon the platform adopted at Nicaea in 325, was finally established as the sole official religion of the state, and heathen worship was put under the ban. The union between Church and State thus constituted continued unbroken in the East throughout the middle ages. The division of the Empire resulted finally in the division of the Church, which was practically complete by the end of the 6th century, but was made official and final only in 1054, and the Eastern and Western halves, the Greek Catholic and the Roman Catholic Churches, went each its separate way. (See Theodosian Code, book 16, for the various imperial edicts relating to the Church, and for fuller particulars touching the relation between Church and Empire see the articles [Constantine]; [Gratian]; [Theodosius]; [Justinian].)
For a long time after the establishment of Christianity as the state religion, paganism continued strong, especially in the country districts, and in some parts of the world had more adherents than Christianity, but at length the latter became, at any rate nominally, the faith of the whole Roman world. Meanwhile already before the beginning of the 3rd century it went beyond the confines of the Empire in Asia, and by the end of our period was strong in Armenia, Persia, Arabia and even farther east. It reached the barbarians on the northern and western borders at an early day, and the Goths were already Christians of the Arian type before the great migrations of the 4th century began. Other barbarians became Christian, some in their own homes beyond the confines of the Empire, some within the Empire itself, so that when the hegemony of the West passed from the Romans to the barbarians the Church lived on. Thenceforth for centuries it was not only the chief religious, but also the chief civilizing, force at work in the Occident. Losing with the dissolution of the Western Empire its position as the state church, it became itself a new empire, the heir of the glory and dignity of Rome, and the greatest influence making for the peace and unity of the western world.
2. The Christian Life.—The most notable thing about the life of the early Christians was their vivid sense of being a people of God, called and set apart. The Christian Church in their thought was a divine, not a human, institution. It was founded and controlled by God, and even the world was created for its sake (cf. the Shepherd of Hermas, Vis. ii. 4, and 2 Clement 14). This conception, which came over from Judaism, controlled all the life of the early Christians both individual and social. They regarded themselves as separate from the rest of the world and bound together by peculiar ties. Their citizenship was in heaven, not on earth (cf. Phil. iii. 20, and the epistle to Diognetus, c. 5), and the principles and laws by which they strove to govern themselves were from above. The present world was but temporary, and their true life was in the future. Christ was soon to return, and the employments and labours and pleasures of this age were of small concern. Some went so far as to give up their accustomed vocations, and with such Paul had to expostulate in his epistles to the Thessalonians. A more or less ascetic mode of life was also natural under the circumstances. Not necessarily that the present world was evil, but that it was temporary and of small worth, and that a Christian’s heart should be set on higher things. The belief that the Church was a supernatural institution found expression in the Jewish notion of the presence and power of the Holy Spirit. It was believed among the Jews that the Messianic age would be the age of the Spirit in a marked degree, and this belief passed over into the Christian Church and controlled its thought and life for some generations. The Holy Spirit was supposed to be manifest in various striking ways, in prophecy, speaking with tongues and miracle working. In this idea Paul also shared, but he carried the matter farther than most of his contemporaries and saw in the Spirit the abiding power and ground of the Christian life. Not simply in extraordinary phenomena, but also in the everyday life of Christians, the Holy Spirit was present, and all the Christian graces were the fruits (cf. Gal. v. 22). A result of this belief was to give their lives a peculiarly enthusiastic or inspirational character. Theirs were not the everyday experiences of ordinary men, but of men lifted out of themselves and transported into a higher sphere. With the passing of time the early enthusiasm waned, the expectation of the immediate return of Christ was widely given up, the conviction of the Spirit’s presence became less vivid, and the conflict with heresy in the 2nd century led to the substitution of official control for the original freedom (see below). The late 2nd century movement known as Montanism was in essence a revolt against this growing secularization of the Church, but the movement failed, and the development against which it protested was only hastened. The Church as an institution now looked forward to a long life upon earth and adjusted itself to the new situation, taking on largely the forms and customs of the world in which it lived. This did not mean that the Church ceased to regard itself as a supernatural institution, but only that its supernatural character was shown in a different way. A Christian was still dependent upon divine aid for salvation, and his life was still supernatural at least in theory. Indeed, the early conviction of the essential difference between the life of this world and that of the next lived on, and, as the Church became increasingly a world-institution, found vent in monasticism, which was simply the effort to put into more consistent practice the other-worldly life, and to make more thoroughgoing work of the saving of one’s soul. Contributing to the same result was the emphasis upon the necessity of personal purity or holiness, which Paul’s contrast between flesh and spirit had promoted, and which early took the supreme place given by Christ to love and service. The growing difficulty of realizing the ascetic ideal in the midst of the world, and within the world-church, inevitably drove multitudes of those who took their religion seriously to retire from society and to seek salvation and the higher life, either in solitude, or in company with kindred spirits.
There were Christian monks as early as the 3rd century, and before the end of the 4th monasticism (q.v.) was an established institution both in East and West. The monks and nuns were looked upon as the most consistent Christians, and were honoured accordingly. Those who did not adopt the monastic life endeavoured on a lower plane and in a less perfect way to realize the common ideal, and by means of penance to atone for the deficiencies in their performance. The existence of monasticism made it possible at once to hold up a high moral standard before the world and to permit the ordinary Christian to be content with something lower. With the growth of clerical sacerdotalism the higher standard was demanded also of the clergy, and the principle came to be generally recognized that they should live the monastic life so far as was consistent with their active duties in the world. The chief manifestation of this was clerical celibacy, which had become widespread already in the 4th century. Among the laity, on the other hand, the ideal of holiness found realization in the observance of the ordinary principles of morality recognized by the world at large, in attendance upon the means of grace provided by the Church, in fasting at stated intervals, in eschewing various popular employments and amusements, and in almsgiving and prayer. Christ’s principle of love was widely interpreted to mean chiefly love for the Christian brotherhood, and within that circle the virtues of hospitality, charity and helpfulness were widely exercised; and if the salvation of his own soul was regarded as the most important affair of every man, the service of the brethren was recognized as an imperative Christian duty. The fulfilling of that duty was one of the most beautiful features of the life of the early Church, and it did perhaps more than anything else to make the Christian circle attractive.
3. Worship.—The primitive belief in the immediate presence of the Spirit affected the religious services of the Church. They were regarded in early days as occasions for the free exercise of spiritual gifts. As a consequence the completest liberty was accorded to all Christians to take such part as they chose, it being assumed that they did so only under the Spirit’s prompting. But the result of this freedom was confusion and discord, as is indicated by Paul’s First Epistle to the Corinthians (see chapters xi., xiv.). This led to the erection of safeguards, which should prevent the continuance of the unseemly conditions (on Paul’s action in the matter, see McGiffert’s Apostolic Age, p. 523). Particular Christians were designated to take charge of the services, and orders of worship were framed out of which grew ultimately elaborate liturgies (see [Liturgy]). The Lord’s Supper first took on a more stereotyped character, and prayers to be used in connexion with it are found already in the Didachē (chapters ix. and x.). The development cannot here be traced in detail. It may simply be said that the general tendency was on the one hand toward the elaboration and growing magnificence of the services, especially after the Church had become a state institution and had taken the place of the older pagan cults, and on the other hand toward the increasing solemnity and mystery of certain parts, particularly the eucharist, the sacred character of which was such as to make it sacrilegious to admit to it the unholy, that is, outsiders or Christians under discipline (cf. Didachē, ix.). It was, in fact, from the Lord’s table that offending disciples were first excluded. Out of this grew up in the 3rd or 4th century what is known as the arcani disciplina, or secret discipline of the Church, involving the concealment from the uninitiated and unholy of the more sacred parts of the Christian cult, such as baptism and the eucharist, with their various accompaniments, including the Creed and the Lord’s Prayer. The same interest led to the division of the services into two general parts, which became known ultimately as the missa catechumenorum and the missa fidelium,—that is, the more public service of prayer, praise and preaching open to all, including the catechumens or candidates for Church membership, and the private service for the administration of the eucharist, open only to full members of the Church in good and regular standing. Meanwhile, as the general service tended to grow more elaborate, the missa fidelium tended to take on the character of the current Greek mysteries (see [Eucharist]; Hatch, Influence of Greek Ideas and Usages upon the Christian Church, 1890; Anrich, Das antike Mysterienwesen in seinem Einfluss auf das Christentum, 1894; Wobbermin, Religionsgeschichtliche Studien zur Frage der Beeinflussung des Urchristentums durch das antike Mysterienwesen, 1896). Many of the terms in common use in them were employed in connexion with the Christian rites, and many of the conceptions, particularly that of sharing in immortality by communion with deity, became an essential part of Christian doctrine. Thus the early idea of the services, as occasions for mutual edification through the interchange of spiritual gifts, gave way in course of time to the theory that they consisted of sacred and mysterious rites by means of which communion with God is promoted. The emphasis accordingly came to be laid increasingly upon the formal side of worship, and a value was given to the ceremonies as such, and their proper and correct performance by duly qualified persons, i.e. ordained priests, was made the all-important thing.
4. The Church and the Sacraments.—According to Paul, man is flesh and so subject to death. Only as he becomes a spiritual being through mystical union with Christ can he escape death and enjoy eternal life in the spiritual realm. In the Epistle to the Ephesians the Christian Church is spoken of as the body of Christ (iv. 12 ff., v. 30); and Ignatius, bishop of Antioch, early in the 2nd century, combined the two ideas of union with Christ, as the necessary condition of salvation, and of the Church as the body of Christ, teaching that no one could be saved unless he were a member of the Church (cf. his Epistle to the Ephesians 4, 5, 15; Trall. 7; Phil. 3, 8; Smyr. 8; Magn. 2, 7). Traces of the same idea are found in Irenaeus (cf. Adv. Haer. iii. 24, 1, iv. 26, 2), but it is first clearly set forth by Cyprian, and receives from him its classical expression in the famous sentence “Salus extra ecclesiam non est” (Ep. 73, 21; cf. also Ep. 4, 4; 74, 7; and De unitate ecclesiae, 6: “habere non potest Deum patrem qui ecclesiam non habet matrem”). The Church thus became the sole ark of salvation, outside of which no one could be saved.
Intimately connected with the idea of the Church as an ark of salvation are the sacraments or means of grace. Already as early as the 2nd century the rite of baptism had come to be thought of as the sacrament of regeneration, by means of which a new divine nature is born within a man (cf. Irenaeus, Adv. Haer. i. 21, 1, iii. 17, 1; and his newly discovered Demonstration of the Apostolic Teaching, chap. 3), and the eucharist as the sacrament of the body and blood of Christ, feeding upon which one is endowed with immortality (cf. Irenaeus, Adv. Haer. iv. 18, 5, v. 2, 2). In the early days the Church was thought of as a community of saints, all of whose members were holy, and as a consequence discipline was strict, and offenders excluded from the Church were commonly not readmitted to membership but left to the mercy of God. The idea thus became general that baptism, which had been almost from the beginning the rite of entrance into the Church, and which was regarded as securing the forgiveness of all pre-baptismal sins, should be given but once to any individual. Meanwhile, however, discipline grew less strict (cf. the Shepherd of Hermas, Vis. v. 3; M. iv. 7; Sim. viii. 6, ix. 19, 26, &c.); until finally, under the influence of the idea of the Church as the sole ark of salvation, it became the custom to readmit all penitent offenders on condition that they did adequate penance. Thus there grew up the sacrament of penance, which secured for those already baptized the forgiveness of post-baptismal sins. This sacrament, unlike baptism, might be continually repeated (see [Penance]). In connexion with the sacraments grew up also the theory of clerical sacerdotalism. Ignatius had denied the validity of a eucharist administered independently of the bishop, and the principle finally established itself that the sacraments, with an exception in cases of emergency in favour of baptism, could be performed only by men regularly ordained and so endowed with the requisite divine grace for their due administration (cf. Tertullian, De Exhort. cast. 7; De Bapt. 7, 17; De Praescriptione Haer. 41; and Cyprian, Ep. 67. For the later influence of the Donatist controversy upon the sacramental development see [Donatists]). Thus the clergy as distinguished from the laity became true priests, and the latter were made wholly dependent upon the former for sacramental grace, without which there is ordinarily no salvation (see [Order, Holy]).
5. Christian Doctrine.—Two tendencies appeared in the thought of the primitive Church, the one to regard Christianity as a law given by God for the government of men’s lives, with the promise of a blessed immortality as a reward for its observance; the other to view it as a means by which the corrupt and mortal nature of man is transformed, so that he becomes a spiritual and holy being. The latter tendency appeared first in Paul, afterwards in the Gospel and First Epistle of John, in Ignatius of Antioch and in the Gnostics. The former found expression in most of our New Testament writings, in all of the apostolic fathers except Ignatius, and in the Apologists of the 2nd century. The two tendencies were not always mutually exclusive, but the one or the other was predominant in every case. Towards the end of the 2nd century they were combined by Irenaeus, bishop of Lyons. To him salvation bears a double aspect, involving both release from the control of the devil and the transformation of man’s nature by the indwelling of the Divine. Only he is saved who on the one hand is forgiven at baptism and so released from the power of Satan, and then goes on to live in obedience to the divine law; and on the other hand receives in baptism the germ of a new spiritual nature and is progressively transformed by feeding upon the body and blood of the divine Christ in the eucharist. This double conception of salvation and of the means thereto was handed down to the Church of subsequent generations and became fundamental in its thought. Christianity is at once a revealed law which a man must keep, and by keeping which he earns salvation, and a supernatural power whereby his nature is transformed and the divine quality of immortality imparted to it. From both points of view Christianity is a supernatural system without which salvation is impossible, and in the Christian Church it is preserved and mediated to the world.
The twofold conception referred to had its influence also upon thought about Christ. The effect of the legal view of Christianity was to make Christ an agent of God in the revelation of the divine will and truth, and so a subordinate being between God and the world, the Logos of current Greek thought. The effect of the mystical conception was to identify Christ with God in order that by his incarnation the divine nature might be brought into union with humanity and the latter be transformed. In this case too a combination was effected, the idea of Christ as the incarnation of the Logos or Son of God being retained and yet his deity being preserved by the assertion of the deity of the Logos. The recognition of Christ as the incarnation of the Logos was practically universal before the close of the 3rd century, but his deity was still widely denied, and the Arian controversy which distracted the Church of the 4th century concerned the latter question. At the council of Nicaea in 325 the deity of Christ received official sanction and was given formulation in the original Nicene Creed. Controversy continued for some time, but finally the Nicene decision was recognized both in East and West as the only orthodox faith. The deity of the Son was believed to carry with it that of the Spirit, who was associated with Father and Son in the baptismal formula and in the current symbols, and so the victory of the Nicene Christology meant the recognition of the doctrine of the Trinity as a part of the orthodox faith (see especially the writings of the Cappadocian fathers of the late 4th century, Gregory of Nyssa, Basil and Gregory Nazianzen).