Early Christianity & the Early Saints:
Scotland has been a predominantly Christian nation since the time of Roman occupation to present day, the religion probably having first come to the country around the second century A.D. Pre-Christian Pictish religion resembled the rest of Celtic polytheism, and it took several hundred years for Christianity to firmly cement itself over the old religion of the ruling class. Tradition maintains that Christianity was first brought to Scotland around 400 A.D. by Saint Ninian, who was born in the Cumbria region and journeyed to Rome as a young man to study Christianity. He attained the status of bishop under Pope Siricius, who charged him with the task of converting the Pictish tribes of Scotland.
Ninian, in legend cited as the first Christian to venture north of Hadrian's Wall, established a base at Whithorn in the southwest of Scotland. He began his missionary work among the Northern Brythons of the surrounding area before undertaking his long journey along the eastern coast of Scotland, spreading the Gospel among the Picts. During his travels, which may have taken him as far north as the Shetland Islands, Ninian trained many missionaries as he spread the monastic tradition throughout Scotland.
Within a century of Saint Ninian's death (which occurred around 432 A.D.), the church he established at Whithorn became Scotland's centre of monastic education. However, after the Roman legions departed the British Isles in 410 A.D., Christian Britannia was left to defend itself against the pagan Saxon tribes who were invading from the Continent. The Anglo-Saxon invasion destroyed most remnants of Roman civilization in Britain, including its economic and religious structures. Existing in relative isolation until the Norman Conquest of 1066, British Christianity developed some peculiarities that made it difficult for the Holy See to extend its full authority into the Isles.
Under the guiding influence of Irish missionaries, the Church in Britain rejected bishoprics in favour of monasteries, calculated a different date for Easter than the one suggested by Rome, and differed on the style of the tonsure haircut worn by its clerics. In Scotland, the Picts did not cling to Christianity long after Saint Ninian left them, and retained most of their pagan customs until Saint Columba arrived in the sixth century.