Gaelic crosses, Cashel, Ireland

Christianity appears to have come to the British Isles with missionaries from Rome or Gaul as early as the second or third century. Through the fourth century this church seems to have been a church of the poor and to have been quite isolated from the mainstream of Roman Christianity in Europe. It developed a strongly independent way of faith and life notable for strenuous asceticism, prominent monasteries, the great power of abbots, itinerant bishops, and a local method for dating Easter. The arrival of Saxons in the fifth century weakened Celtic Christianity. Augustine of Canterbury arrived in England in the seventh century as a missionary of Roman Christianity. At the Synod of Whitby (664) Celtic Christians agreed to submit to Roman Catholic norms. The Celtic church was the principal source of Christian missionaries to Europe during the sixth and seventh centuries. One of the most important centers of missionary energy was the monastery of Iona off the Scottish coast. Its founding abbot, Columba, himself made missionary journeys to Europe.