Christianity in Medieval Scotland includes all aspects of Christianity in the modern borders of Scotland in the Middle Ages. Christianity was probably introduced to what is now Lowland Scotland by Roman soldiers stationed in the north of the province of Britannia. After the collapse of Roman authority in the fifth century, Christianity is presumed to have survived among the British enclaves in the south of what is now Scotland, but retreated as the pagan Anglo-Saxons advanced. Scotland was largely converted by Irish missions associated with figures such as St Columba, from the fifth to the seventh centuries. These missions founded monastic institutions and collegiate churches that served large areas. Scholars have identified a distinctive form of Celtic Christianity, in which abbots were more significant than bishops, attitudes to clerical celibacy were more relaxed and there were significant differences in practice with Roman Christianity, particularly the form of tonsure and the method of calculating Easter, although most of these issues had been resolved by the mid-seventh century. After the reconversion of Scandinavian Scotland in the tenth century, Christianity under papal authority was the dominant religion of the kingdom. In the Norman period, from the eleventh to the thirteenth centuries, the Scottish church underwent a series of reforms and transformations. With royal and lay patronage, a clearer parochial structure based around local churches was developed. Large numbers of new monastic foundations, which followed continental forms of reformed monasticism, began to predominate. The Scottish church also established its independence from England, developing a clear diocesan structure and becoming a "special daughter of the see of Rome", but continued to lack Scottish leadership in the form of Archbishops. In the late Middle Ages the problems of schism in the Catholic Church allowed the Scottish Crown to gain greater influence over senior appointments and two archbishoprics had been established by the end of the fifteenth century. Historians have discerned a decline in traditional monastic life in the late Middle Ages, but the mendicant orders of friars grew, particularly in the expanding burghs, emphasised preaching and ministering to the population. New saints and cults of devotion also proliferated. Despite problems over the number and quality of clergy after the Black Death in the fourteenth century, and evidence of heresy in the fifteenth century, the Church in Scotland remained stable before the Reformation in the sixteenth century. Early Middle Ages Early Christianisation Before the Middle Ages, most