But while traders of the Empire sailed to Ireland, the armies of Rome never crossed the Irish Sea. Ireland therefore lay outside the Roman Empire, while it lay within the circle of imperial civilisation and commerce. Christianity first came from across the Gaulish Sea, and the art of writing, and new forms of ornament. From Gaul the Irish learned to divide tribe-land into private property marked by boundary stones. Roman-Hellenistic learning, which spread from northern Italy to Marseilles, crossed the Irish seas with the merchants of Aquitaine carrying the wine of Bordeaux; or it was brought home by Irish scholars of the fourth century who went to seek learning in Narbonne, where Greek was spoken as a living tongue. The Irish Pelagius, who went to Italy in 400, was able to carry on a discussion in Jerusalem in 415 with Orosius the Spaniard, in which he spoke Greek while Orosius needed an interpreter: if he had not learned Greek in Ireland, Zimmer reminds us, he would not have been able to learn it in Rome. Nearly two hundred years later, in 595, the Irish saint Columbanus and his companions knew Greek, but Gregory the Great did not know it, though he had twice been Papal nuncio in Constantinople. Ovid and Vergil were known and read in Ireland, where scholars seem to have taken all that Rome had to give of classical culture and philosophy. It is often assumed that to share in the benefits of an empire it is necessary to be a subject country, lying within its police control, and that the Irish suffered by never having been forced under the authority of Rome. Perhaps, however, we might learn here another lesson--that in matters of civilisation what is really needed is not subjection to force, but free human converse and the willing intercourse of men. We have the spectacle of an island beyond the military rule, the police control, the law, of the Roman empire, willingly adopting all the spiritual good which Rome could give it, and the culture that the intelligence of its people found to suit them. Free to keep her own customs, Ireland could gain this new learning without losing her own civilization and her pride of language, history, and law. It was in seas of blood that such national pride was wiped out by Roman conquerors from the plains of Gaul. But for the Irish at that time there was no violent breach with the traditions of their race, nor any humiliation or bondage to darken their high spirit; and in the joyful and brilliant activity of the succeeding centuries they illustrated the free and peaceful union of two civilizations.