To understand the conversion of Ireland, which we are here considering as an episode in the history of Europe, we must glance at the general conditions of the early propagation of the Christian idea. It would not be easy to determine how much Christianity owes to the Roman Empire, and we can hardly imagine what the rate and the mode of its progress through southern and western Europe would have been if these lands had not been united and organised by the might of Rome. It is perhaps not an exaggeration to say that the existence of the Empire was a condition of the success of a universal religion in Europe; and it is assuredly true that the hindrances which the Roman Government, for two centuries and a half, opposed to its diffusion, by treating it as the one foreign religion which could not be tolerated by the State, were more than compensated by the facilities of steady and safe intercourse and communication, which not only helped the new idea to travel, but enabled its preachers and adherents to organise their work and keep in constant touch with one another. The manner in which this faith spread in the west, and the steps in its progress, are entirely hidden from us; we can only mark, in a general way, some stages in the process.[2] We know that there were organised communities in Gaul in the second century, and organised communities in Britain at the end of the third; but in neither of these countries, it would seem, did the religion begin to spread widely till after its official recognition by the Emperor Constantine. At the end of the fourth century there were still large districts in Gaul, especially in the Belgic provinces, which were entirely heathen. In this respect Gaul and Britain present a notable contrast to the other great Atlantic country of the Empire. In the Spanish peninsula Christianity made such rapid strides, and the Spaniards adapted it so skilfully to their pagan habits, that before the time of Constantine Spain had become, throughout its length and breadth, a Christian land. [Sidenote: CAPTIVES]