I can hear the howls of outrage. But before you grab torches and pitchforks and head over to my house, give me a moment. Obviously, Patrick was not an atheist when he began his world-changing missionary work. Yet by his own admission, there was a time in his life when his likelihood of ever being venerated as a saint was nil.

In 401, the great St. Augustine of Hippo wrote the Western world’s first autobiography, his Confessions. A few decades later St. Patrick followed suit, although, sadly, Patrick’s Confession is not nearly as detailed as Augustine’s. Nonetheless, it is full of interesting information about Patrick’s family, his youth, and a near-apostolate-destroying scandal that turned his fellow bishops against him.

Patrick tells us he was born in a Roman settlement called Bannavern Taburniae on the British side of the Irish Sea. More than that we do not know—archaeologists have never found the site. Patrick’s mother, Concessa, and his father, Calpornius, were devout Christians who brought their son up in the faith and taught him the Scriptures. Calpornius was a deacon; his father, Potitus, had been a priest. In spite of his parents’ best efforts, Christianity made no discernible impact on Patrick. Late in life when he wrote his Confession he recalled his youth and admitted candidly, “I did not believe in the living God.”

Patrick went on to acknowledge that when he was fifteen he did something so wicked that years later, when he was about to be ordained a deacon, he worried that perhaps this old sin barred him from ordination. He disclosed the secret to his closest friend, who reassured Patrick that as he had long since repented of this sin, there was no impediment to receiving holy orders. This unnamed friend promised most solemnly never to repeat what Patrick had told him.

What had the teenage Patrick done that years later his conscience still troubled him? That question has tantalized historians and hagiographers for 1600 years. Patrick himself doesn’t give us much of a hint. He says it was something “I had done in my boyhood one day, nay, in one hour, because I was not yet strong.” The traditional interpretation has been that Patrick had some kind of sexual encounter. That is a possibility. In any case, Patrick followed his friend’s advice and was ordained a deacon, then priest, and eventually he was consecrated bishop.

It was after Patrick became a bishop that word of his indiscretion became common knowledge—apparently his best friend was not very good at keeping a secret. The bishops of Britain and Gaul (modern-day France), to use Patrick’s word, “attacked” him, and started proceedings to strip him of his ecclesiastical rank. “Not slight,” Patrick said, indulging in a bit of understatement, “was the shame and blame that fell upon me.”

 If Patrick’s sin had been a teenage romantic fling, then the bishops were over-reacting. Which brings us back to our original question: What did Patrick do?

Recently, students of St. Patrick’s life and times have suggested that the great sin of his youth was serious indeed. There’s a best-guess consensus that Patrick, although technically a Christian, took part in a pagan ceremony. Such an offense truly would be bad enough that an old friend might feel obliged to reveal it, and members of the hierarchy might call for Patrick’s removal from office.

The apostles had forbidden the first Christians to have anything to do with pagan rites. Their prohibition even extended to eating part of any food that had been offered as a sacrifice to false gods. In Patrick’s Britain the old pagan rites were ubiquitous, while Christianity was the strange, new, minority religion. In the eyes of the Church, joining a dance around an oak tree, or attending a sacrifice to a British god would count as participation in idolatry. For a teenage boy who did not believe in God, a pagan festival probably looked less like an unholy rite and more like a party he didn’t want to miss.

And then there is another question: How did an unbelieving, quasi-pagan youth become the great Apostle of Ireland and one of the Church’s most renowned saints?

When Patrick was sixteen, a band of Irish raiders landed on the western coast of Britain near Bannavern. They looted Calpornius and Concessa’s villa, and carried off captives, Patrick among them.

In Ireland Patrick was sold into slavery and put to work watching sheep. Forced to live outdoors, exposed to heat and rain and cold, under-clothed, under-fed, far from home and with no hope of ever escaping from an island he described as “the utmost part of the earth,” the boy was on the point of despair. Yet in that dark time Patrick at last remembered God. “The Lord opened the sense of my unbelief,” he recalled, “that I might at last remember my sins and be converted with all my heart to the Lord my God.” Perhaps for the first time since he was a child, Patrick began to pray, and with such fervor that, as he tells us, as long as he was in conversation with God he was senseless to frost and snow and rain. He says that he found the consolations of prayer so sweet he would offer one hundred prayers during the day, and another hundred at night.

After six years in slavery, Patrick heard a voice say, “See, your ship is ready.” At once, Patrick left the sheep and ran off to find the ship that would carry him home. When he arrived at the coast there was a ship preparing to leave, but the captain refused to take him aboard. As Patrick walked away, he prayed. He had not even finished the prayer before one of the crew called him back. “We will take you on,” the sailor said. “Make friends with us.”

It was a long, round-about journey before Patrick made his way back to his family in Bannavern. Nor did he remain at home long. One night he had a dream in which a stranger gave him a letter that bore the inscription, “The Voice of the Irish.” When he opened it he heard a multitude crying, “We beg you, holy youth, come and walk among us once more!” Certain of his vocation, Patrick left his home for Gaul to study for the priesthood in preparation for his return to Ireland as a missionary.

By the time Patrick was ordained there were a few Christians in Ireland, probably near present-day Wicklow. The size of this enclave was small, but numerous enough to prompt the pope to send them a bishop named Palladius. He visited the Christians of Ireland, then sailed off to see the Christians of southwest Scotland. Before Palladius could return to the Christian Irish, before he sent a single mission to the pagan Irish, he died.

In 430s, Patrick was ready to bring the faith to Ireland. He sold his patrimony to fund his mission and sailed across the Irish Sea, most likely coming ashore in Ulster (in his Confession, Patrick is maddeningly imprecise about places). He traveled extensively in Ulster, Leinster, and Munster; he may have gotten to Connaught on the west coast of Ireland, but that is uncertain. Yet everywhere he went he was astonished by the fervor with which the Irish responded to the gospel. In imagery that recalls St. Peter the fisherman Patrick said, “[we] spread our nets so a great multitude and throng might be caught for God.” Even more marvelous to him were the numbers of young men and women, many from the leading families of the country, who not only asked for baptism, but begged to be permitted to take vows as monks and nuns.

If anything reveals the depth of Patrick’s attachment to his converts it the blistering letter he wrote to Coroticus, a Christian British prince who raided a Christian Irish community, killing many of the faithful and carrying off the survivors to sell as slaves. Patrick denounced Coroticus and his men as “fellow citizens of the demons…. Dripping with blood, [you] welter in the blood of innocent Christians whom I have begotten into number for God and confirmed in Christ.” In another passage it is obvious that the memories of his own years as a slave are still raw in Patrick’s mind. “You… sell [Christians] to a foreign nation that has no knowledge of God. You betray the members of Christ as it were into a brothel.”

There is no record that Coroticus ever released his captives, or that Patrick ever saw those beloved converts again.

We know that Patrick died on March 17, but we are not certain of the year: based on the surviving records, 461 is as good a guess as any. He died justly proud of how far he managed to carry the faith among the Irish. In the centuries since Patrick’s day, the Irish have carried that faith to every corner of the globe. In modern times, to the United States and Canada, of course, and to England, Scotland, and Wales. Irish clergy, religious, and laity also planted the faith in Australia, New Zealand, Africa and Asia. And wherever there are communities of Irish, invariably they build a church, and more often than not, they dedicate it to St. Patrick.

This article originally appeared at the Register on March 17, 2017.