St Patrick arrived in Ireland as a missionary in 432 a.d. but had previously been in Ireland as a teenager when he was enslaved by Ulster tribesmen at the age of 15, by his own account. It is possible to conjecture that he acquired a deep knowledge of Gaelic culture before his escape some years later but, more likely, he learnt the language and the institutions and decided or afterwards to revisit the country as a Christian missionary. (He was, after all, the son of a British deacon.) In either case, it is clear that his relations with the native kingships and, more generally, with their cultural traditions, was such that he did not seek to uproot them from the hearts and minds of those whom he converted to the new religion. Saint Patrick's Confession and his Letter to the Soldiers of Coroticus - the only extant texts truly known to have been written or dictated by him - shows him a devout believe in the immortal soul and its final judgement at the hands of God but it also shows him as a sympathetic figure who is capable of appreciating human suffering and human joy - as well as an example of remarkable modesty about his own attainments in scholarship and learning.
The Saint Patrick whom we meet with in the Tripartite Life is, all considered, a powerful magician with greater magic spells than the druids whom he overcomes. It is probable that those feats of supernatural prowess - especially in dispelling an eclipse brought on by the druids who seem able to bring it on but powerless undo it, represent the substitution of a pagan by a Christian calendar and, more specifically, the liturgical calendar which revolves around the Feast of Easter. (Light is never just light in religious narratives.) To our eyes - and those of all his modern admirers - St. Patrick is more like a practical man with a message that a wonder-working saint and it is his rational approach to the business of conversion that holds our attention. We grasp that the real St Patrick stepped into a mythopoeic world in Ireland when he crossed the Irish sea in the 5th century. Britain had been colonised by the Romans and had thereby come to share in the ethos of centralised administration and classical culture - a culture dominated by philosophy rather than by mythology. Ireland, by contrast, was still a pagan country, ruled by a complex system of petty kingships and immersed in mythological habits of thought which he had to negotiate by any means he could.
One such means was, for instance, the use of the trefoil (shamrock) as an allegory of the Holy Trinity. Another was his determination to Christianise every well in the country - a transformation that seemingly got to the very root of Gaelic life in its vital association with the source of fresh water which made any place sanitary and desireable for the Gaelic population. (Sweet water is a constant feature of Early Irish poetry.) For Patrick, son of Calpurnus, the challenge was to exploit both of these aspects of his life-experience in order to build a Celtic church in Ireland - a church which would have a crucial impact on the the wider world and the future of civilisation when its missionaries began to travel to the Continent to renew the Christian faith and classical learning which had been lost during the so-called Dark Ages when the spirit of the Vikings and their rude heirs ruled in Western Europe.