According to tradition dating from the early Middle Ages, Patrick is credited with bringing Christianity to Ireland. According to Patrick's autobiographical Confessio, when he was about sixteen, he was captured by Irish pirates from his home in Britain and taken as a slave to Ireland. He writes that he lived there for six years as an animal herder before escaping and returning to his family. After becoming a cleric, he returned to spread Christianity in northern and western Ireland. In later life, he served as a bishop, but little is known about where he worked. By the seventh century, he had already come to be revered as the patron saint of Ireland.