Now what was the cause of this wonderful progress? It is easy to say what was not its cause. Physical force and the authority of the Government had nothing to do with it. Its missionaries did not preach with sword in hand, nor were they backed up by the civil power. All they did, all they could do, was to appeal to man's reason and conscience, and this appeal was successful. And we learn from the Christians' themselves, e.g., in the Acts, that there were two main reasons for this. The first was the confident appeal to the facts of Christianity, such as the Resurrection of Christ, as undisputed and indisputable; and the second was the occasional aid of miracles. And the more we reflect on the subject, the more difficult it is to account for it, without at least one of these causes. For the spread of Christianity was not like that of a mere philosophy, or system of morals. It depended entirely on certain alleged matters of fact, which facts were quite recent at the time of its origin, occurred at the very place where it was first preached, and were open to the hostile criticism of an entire nation. This, it is needless to say, is without a parallel in history.
But it may be said, notwithstanding this rapid progress at first, Christianity took nearly three centuries to conquer the civilised world. Undoubtedly it did, but the significance of the conquest is not diminished by this. It is rather increased when we remember that at intervals all through this period the Religion suffered the fiercest persecution. That it should have survived such a fearfully prolonged struggle, and have finally conquered, does but show its inherent strength. We may look in vain for anything like this in the rest of history. No other religion has ever withstood such persistent attacks; no other religion has ever obtained such a complete and almost incredible triumph, the Emperor of the civilised world being brought to worship One Who had been put to death as a malefactor. In short, the progress of Christianity was as unique as its origin, and can only be satisfactorily accounted for by its truth.
(3.) The so-called natural causes of success.
We must next glance at some natural causes which have been alleged as accounting for the wonderful spread of Christianity. Those brought forward by Gibbon in his Decline and Fall of the Roman Empire ([Chapter XV.]) are five in number. The first is the intense zeal of the early Christians. And doubtless this was a most important element in spreading their religion. But what gave them this intense zeal? What was it that made them so fearfully in earnest about their new religion, that they faced a life of suffering, and a death of martyrdom in preaching it? There can be but one answer. It was because they were so absolutely convinced of its truth. It was vouched for by what they considered overwhelming evidence, so they willingly risked everything for it. Their zeal, then, is but evidence for their conviction, and their conviction is but evidence for the truth of what they were convinced of; and valuable evidence too, for they plainly had much better means of knowing about it, than any that we can have.
Secondly, there is the doctrine of a future life; and doubtless this also had much to do with the success of Christianity. A longing for immortality seems inherent in man, and the vague guesses of philosophers were quite unable to satisfy this. It might be true that men should live again, but that was all they could say. Christianity alone, resting on the actual fact of Christ's Resurrection, said it was true; so here men found the assurance they wanted. But is it likely that Christianity should have so thoroughly satisfied them in this respect, had there been any real doubt as to Christ's Resurrection?
Thirdly, we have the miracles ascribed to the early Christians. Gibbon's argument here is more difficult to follow. Of course if these miracles were true, they would have greatly assisted the new religion; but then they would have been, not a natural but a supernatural cause of success. If on the other hand, the miracles were false, it is hard to see how the early Christians could have helped their religion by claiming miraculous powers which they did not possess, and which their contemporaries must have known that they did not possess.
Fourthly, we have the pure morality taught and practised by the early Christians. And no doubt this had something to do with helping their religion. But again we must ask, what was it that enabled the Christians alone in that age of vice and wickedness to lead pure lives? They ascribed it themselves to the example and power of their Founder, and nothing else can account for it. Christian morality cannot be a stream without a source, and no other source can be assigned to it. But could a mere human Teacher have had this more than human influence over thousands of converts, most of whom had never seen him?
Lastly, comes the union and discipline of the early Church. This may have helped Christianity in the later stages of the struggle, but could obviously have been of little use at the commencement. Moreover, why should Christians of various nations and classes have been so thoroughly united on this one subject, unless they were convinced of its overwhelming importance? On the whole, then, these so-called natural causes of success are at most only secondary causes; the truth of the religion is what they all imply, and this is the real cause which alone can account for its success.
A better way of explaining the spread of Christianity, which is now often adopted, is by saying that it arose at a favourable crisis. The dispersion of the Jews throughout the known world would, it is urged, have facilitated the spread of a religion founded by Jews. The speculations of the Greeks as to a Divine Word, or Logos, would have prevented the doctrines of the Trinity, and the Incarnation, from forming any great difficulty to the learned classes. While the mass of the people were disgusted with the old mythologies of Greece and Rome. These were dying out, because they failed to satisfy human nature, and men were longing for something better. They wanted, as men always will want, a religion; but they wanted it free from the absurdities and immoralities of Pagan worship. Christianity then appeared, and as it was found by many to meet the demand, it naturally succeeded.
In answer to this it must be remembered that Christianity was not a religion founded at Rome or Athens, in which case it might perhaps be said that the demand caused the supply; but it arose as a small Jewish sect in Palestine. While the fierce persecutions it had to endure show that it did not obviously meet the requirements of the day, even apart from the tremendous difficulties involved in the worship of the Crucified. But now suppose, for the sake of argument, that this had been otherwise, and that the world was so suited to receive Christianity as to account for its rapid spread; would the inference be against its Divine origin? Certainly not; for the agreement in this case would be far too close to be accidental. It must have been designed. And it would thus show that the God Who rules in history, is also the God Who introduced Christianity. So here again the proposed explanation, even if admitted, does but imply the truth of the religion.