Hiberno-Scottish mission

In the 6th and 7th centuries, the Hiberno-Scottish mission saw Gaelic missionaries from Ireland spread Celtic Christianity across Scotland, Wales, England, and Merovingian France. Initially, Catholic Christianity spread within Ireland itself. The term "Celtic Christianity," which emerged in the 8th and 9th centuries, is somewhat misleading. Catholic sources argue that these missions operated under the Holy See's authority, while Protestant historians emphasize conflicts between Celtic and Roman clergy, noting the lack of strict coordination in these missions. Despite regional variations in liturgy and structure, Celtic-speaking areas maintained a strong veneration for the Papacy.

Dunod, a disciple of Columba, founded a significant Bible school at Bangor-on-Dee in 560. This school was notable for its large student body, organized under seven deans, each overseeing at least 300 students. The mission faced conflict with Augustine, sent by Pope Gregory I to Britain in 597 with authority over British bishops. At a conference, Deynoch, the abbot of Bangor, resisted Augustine's demand to submit to Roman Church ordinances, stating their readiness to listen to the Church and the Pope but rejecting the necessity of absolute obedience to Rome. Representatives from Bangor upheld their ancient customs and rejected Augustine's supremacy.

In 563, St. Columba, along with companions, traveled from Donegal to Caledonia, founding a monastery on Iona. Under Columba's leadership, the monastery flourished and became a center for evangelizing the Dalriadian Scots and the Picts. By Columba's death in 597, Christianity had spread throughout Caledonia and its western isles. In the subsequent century, Iona prospered, and its abbot, St. Adamnan, wrote the "Life of St. Columba" in Latin. From Iona, missionaries like the Irish Aidan continued the spread of Christianity to Northumbria, Mercia, and Essex.

In England, Aidan, educated at Iona, was invited by King Oswald in 634 to teach Celtic Christianity in Northumbria. Oswald granted him Lindisfarne to establish a Bible school. Aidan’s successors, Finan and Colman, continued his work, spreading the mission across the Anglo-Saxon kingdoms. It is estimated that two-thirds of the Anglo-Saxon population converted to Celtic Christianity during this time.

Columbanus, born in 543, studied at Bangor Abbey until around 590 before traveling to the continent with twelve companions. Welcomed by King Guntram of Burgundy, they established schools at Anegray, Luxeuil, and Fontaines. Expelled by Theuderic II in 610, Columbanus moved to Lombardy, founding a school at Bobbio in 614. His disciples founded numerous monasteries across France, Germany, Belgium, and Switzerland, including St. Gall in Switzerland and Disibodenberg in the Rhine Palatinate.

In Italy, significant figures from this mission included Saint Donatus of Fiesole and Andrew the Scot. Other notable missionaries included Fridolin of Säckingen, who founded monasteries in Baden and Konstanz, and figures like Wendelin of Trier, Saint Kilian, and Rupert of Salzburg, who contributed to the spread of Celtic Christianity across Europe.