Tradition holds he was taken captive as a teenager by Irish pirates from his native Britain. He eventually escaped but after some time he saw a vision and came back to Ireland to be a missionary. When he came back, he became active in baptizing and spreading Christianity. Interestingly, an early 7th century letter written by Columbanus, an Irish missionary, states that Christianity came to Ireland via Palladius. Works by Tírechán, writing later in the 7th century, then begin to attribute Christianity brought to Ireland via Patrick. The writer refers to <i>Book of Ultán</i>, which could be a missing or lost source regarding Patrick, as this work no longer survives. Many of the conversion stories mimic other conversion stories found in the late Roman Empire, suggesting that many of the stories were borrowed and attributed to Patrick or even that the stories were combined in relation to Patrick. It may have not been until the 7th century, long after Patrick, that churches and monasteries began to spread across Ireland.
The main tradition that continues to have connection to Saint Patrick is the use of the shamrock to teach about the Holy Trinity. However, that tradition
did not develop until the 1700s, far later than any of the early Medieval writings about Saint Patrick. Other stories, such as snakes being banished from Ireland by Patrick, mask the fact that there have not been snakes in Ireland since the last ice age. The selection of March 17th as Saint Patrick's day relates to the purported date of Patrick, but there is no certainty of that from sources.