I was also interested in the state of Christianity after the destruction of Jerusalem. The following is taken from Adolf von Harnack's treatise The Mission and Expansion of Christianity in the First Three Centuries. I have great respect for German scholarship. Only problem with it, it is quite old (1925), but insightful in that it indicates that not many sources outside the Bible, i.e., the NT, exist that sheds light on that critical time. He tried to piece things together with what he had. Overall, he concentrated on later periods in the development of Christianity. I am still working though the two volumes, but will let you know if I discover anything interesting. In hindsight one can see that the scattering of the early Christians did help in spreading the Christian message to surrounding towns and areas.
The testimonies collected under §§ 1–4, 6–9, and 11 represent the original and ancient conception of the rapid spread of the gospel over all the world. They tell us hardly anything about its actual spread, though they certainly bear witness to its energetic character, and to the fact that the gospel had already reached barbarians, Greeks, and Latins in the course of its diffusion throughout the empire.
§ 3 (Matt. 24:14) contains the general theory of the mission, which is put into the lips of Jesus: “the gospel has to be preached to all the world for a testimony to the heathen. Then comes the end.” The eschatological picture drawn by the author of the Apocalypse (§ 6, Apoc. 7:9) corresponds to this.
The passages from Paul (1 Thess. 1:8; Rom. 1:8, 15:19 f.; Col. 1:6, 23) are deliberate rhetorical exaggerations; so in § 4 (Acts 17:6).
The passages in § 7 (Matt. 24:9, 28:19; Mark 16:20; Acts 1:8; Preaching of Peter) and § 2 (1 Tim. 3:16, quotation from a hymn) affirm that the disciples of Jesus, or the apostles, received a commission to go into all the world and preach the gospel to all men, and that they discharged this commission. This belief, that the original apostles had already preached the gospel to the whole world, is therefore extremely old; nor, even supposing that Matt. 28:19 is taken as an interpolation, need it be put later than c. 90 a.d. (cp. Acts 1:8). The belief would never have arisen unless some definite knowledge of the apostles’ labours and whereabouts (i.e., in the majority of cases) had been current. Both Clemens Romanus (§ 8) and Ignatius (§ 9) assume that the gospel has already been diffused all over the world, the former speaking, with rhetorical exaggeration, of Paul as the missionary who had taught all the world. Finally, as the conception emerges in Hermas (§ 11), it is exceptionally clear and definite; and this evidence of Hermas is all the more weighty, as he may invariably be assumed to voice opinions which were widely spread and commonly received. On earth, as he puts it, there are twelve great peoples, and the gospel has already been preached to them all by the apostles.
The actual expansion of the gospel during the first Century must be deduced from the writings of the New Testament and the earliest extra-canonical literature. With regard to the intensity of its spread, we possess no evidence beyond that of the passages cited under § 5 (Acts 21:20) and § 10 (Pliny). These passages, however, are of extreme importance. The former testifies that among the Palestinian Jews, at the time of Paul’s last visit to Jerusalem (i.e., during the sixth decade), Christians were already to be found in tens of thousands. The latter passage yields even richer spoil. It sketches the compass and consequences of the Christian propaganda in Bithynia and Pontus during the reign of Trajan; it depicts an activity which astounds us and which might dispose us to question Pliny’s statements—particularly as he had good reasons for exaggerating the movement, in order to dissuade the emperor from taking any wholesale, bloody measures for its repression. Still, the main points of the governor’s tale must be correct, and they are quite enough to justify the opinion that exceptionally strong currents were already flowing in these provinces which told in favour of a religion like Christianity (see below, Sect. III. § 9 in the third chapter of this Book).
As the statements of Justin (§ 12) and the author of the epistle to Diognetus (§ 14) upon the diffusion of Christianity are mainly due to the theoretical belief that the gospel must have already spread all over the earth, they are of no value, although the evidence of Dial. cxvii. may perhaps be based on some knowledge of the nomadic Arabs having already been reached by the message of Christianity. Justin, as a native of Samaria, might quite well know something about these tribes. In any case, the other notice is of some importance, viz., that by the age of Justin the Gentile Christians already outnumbered the Jewish Christians. Still more significant, of course, is the statement of pseudo-Clemens (Soter), writing about fifteen years later, to the effect that the Christians were more numerous than the Jews (§ 13). For, even if this notice represents a purely subjective estimate, even if it applies in the first instance only to the special circle which the author had in view (i.e., Rome), still it must remain an illuminating fact that a prominent Roman Christian, circa 170 a.d. , was under the impression that the Christians were already superior numerically to the Jews.
The language employed by Celsus (§ 15) serves as a welcome corrective of the Christian exaggerations. True, Celsus also exaggerates. But he exaggerates in an opposite direction. He makes out as if Christianity were already in extremis owing to the rigour of the imperial regulations under Marcus Aurelius. This, of course, is not worth serious discussion. Nevertheless, the mere fact that he could give vent to such an idea, proves that there was no question as yet of enormous crowds of Christians throughout the empire.
The general theory, that the church had already spread all over the world, also underlies the assertions of Irenæus (§ 17) and Clement of Alexandria (§ 18). Nevertheless, the statements of the latter author deserve consideration, for he met with many people from various quarters, and he testifies, moreover, that “not a few” philosophers had betaken themselves to Christianity. The remarks of Irenæus, again, have some weight as regards the churches in Germany and among the Celts at any rate—however worthless they may be as regards Iberia, etc. On the former churches Irenæus could speak from personal knowledge, and it is they who are meant in his allusions to barbarian tribes who possessed true Christianity, although they had not the scriptures in their own language. [1]
[1] von Harnack, A. (1908). The Mission and Expansion of Christianity in the First Three Centuries, Volume 2 (J. Moffatt, Ed.) (Second, Enlarged and Revised Edition). Theological Translation Library (23–26). London; New York: Williams and Norgate; G. P. Putnam’s Sons.
