For me, pilgrimage begins with the Isle of Iona. I started going there with my parents in the earliest days of childhood. We traveled from the heart of landlocked Perthshire: as the crow flies it’s a couple of wing beats to Iona, while by car it involved a two-hour journey west to Oban, a ferry to the Isle of Mull, a long and beautiful drive across that island, and then a second short ferry crossing to Iona. In those days a small passenger ferry took pilgrims to Iona; I had the sense of reaching the outer edge of some tectonic plate or even the edge of the world.

I felt, doubtless like tens of thousands of Iona pilgrims each year, that I had gone back in time. Iona was a place of remoteness and quiet, little changed, I imagined, from the island Columba found when he landed in the sixth century. I felt its isolation when I walked alone to Sandeels Bay in the middle of the island’s east coast or when I battled against the omnipresent winds to the south end of Iona and St. Columba’s Bay. Despite roads and telephones, this was still the Iona the saint had come to find and from which he and his followers had gone out with the Christian story.

That sense of Iona as an edge place pleased me and stayed with me. I was entirely content with it until one day several years ago when I attended a lecture by an archaeologist in Glasgow.

Ironically, I went to the lecture believing I didn’t have much to learn. I wanted to be polite, certainly, but I knew Iona, my Iona, and I couldn’t imagine anything the archaeologist would say about Columba or the early days of Celtic Christianity was going to change that.

Her first slide was of the island as it lies on the map, in the southern waters of the Hebrides, not many sea miles from the north coast of Ireland. To the east is Mull; beyond that, the channel of water separating Mull from Argyll and the Scottish west coast. But instead of Iona being an edge place, far out at the end of a long journey from an inland town, the map showed that it was at the center of the sea roads.

In a world dominated by asphalt and cars, islands are always edge places. But the Celts were navigators; they knew and understood boats and stars and tides. That map rendered Iona the middle of a network of busy sea life. Now we no longer live by navigating the sea, and many of us have all but forgotten it. But in the sixth century it was the way you traveled and the way things and people came to you. I started listening.

Iona, the archaeologist told us, was far from being a quiet place in the days of Columba and the early Celtic church. Iona became a vibrant place of learning and creating, loud with the excited chatter of scholars. There was the copying of manuscripts, the making of music, the arguing over ideas—and ideas of all kinds, not only religious or philosophical questions. People came to Iona because they had heard that this tiny island off the west coast of Scotland (at a time when Scotland was not a nation yet) was in the process of becoming the beating heart of the Celtic Christian story.

This monastic settlement followed in the footsteps of its many Irish predecessors, places like Clonmacnoise and Clonfert. Like them, it was a very early university. But it wasn’t only about learning and arguing—it was about creating. What vibrancy of life there must have been on Iona at that time; what electricity must have been in the air. Those sea roads would have been ever busy with boats bringing ink for manuscripts, calfskins for vellum, and new scholars and curious visitors alike.

I suspect I felt I had learned enough that day. Enough of what I thought I had known had been knocked down and needed to be rebuilt. But there was more, and perhaps the most important and exciting element of all. The lecturer spoke of hermit monks, those who required absolute quiet in their quest to hear God clearly. For them, Iona became so loud and excited with the chatter of voices that they had to leave. Iona was the starting point for their journeys, not the end place.

I came out of that lecture elated, even though my old ideas were now rubble. The story she had told me surely led to other stories, to roads hitherto unseen. Like those hermit monks, I felt at the beginning of a journey.

If Iona was a center and not an edge, then I was very curious where the hermit monks had gone to listen to God. In recent years, we’ve learned from archaeologists that Tor Abb, the mound of earth right beside the present-day abbey church, was indeed the cell of St. Columba. Now I wondered how often he might have had to get up grumpily in the night to tell scholars arguing excitedly on the moonlit grass to keep their discussion down and let him have some sleep.

Columba would have needed places of retreat, and we need them too: we have to have hideaways where we are able to hear our own thoughts and discern the still, small voice of calm. We are babblers first and listeners second, and we likely always have been. Even though some of us may require the place of talk and vibrant creative energy much of the time, all of us also need the quiet place, the listening place.

Our Lord and Master, the one whose path we yearn to find and follow, required places of solace and silence where the voice of his Father could be heard more easily, and he often went to the desert to pray. Perhaps for this reason, the early Celtic Christians became fascinated by the Desert Fathers. The word desert appears time and again in early Celtic writings, and it came to mean many things—perhaps in part because there wasn’t an actual desert of sand and drought to travel into.

In a world of gnarled rock and wild river and deep forest, surrounded by powerful seas, deserts were largely unknown, so early Celtic Christians turned them into metaphors. One metaphorical desert was the sea. It wasn’t only what lay on the sea’s surface that held danger, storm, and rock and the boats of those who might wish them ill, it was all the unfamiliar creatures beneath the water.

There’s a wonderful account in Adomnan’s Life of Columba in which St. Cormac is out in the waters off Iona, surrounded by strange and terrible creatures. On Iona, Columba perceives his struggle and begins to pray fervently for his life. At last, Cormac is free of the creatures that have beset his vessel. The passage makes clear that the sea, like the desert, was a place where these early Celtic Christians journeyed into the unknown, where they had to trust in God’s safekeeping. (The passage also includes what is reckoned to be the first written account of jellyfish.)

Similarly, the first Celtic Christians had to refashion their understanding of martyrdom. Even as Christianity was introduced to the Celtic world, there were very few instances of martyrdom. But they knew the truth of the saying: The blood of the martyrs is the seed of the Church. So how were they to understand martyrdom in the Celtic world? How was it to be interpreted and practiced so that it built their numbers and their faith?

The early monks used the ideas of desert and martyrdom to create a unique interpretation in their own setting. There were different types of martyrdom created, different grades, but they all involved removing oneself from society and society’s comforts. They imagined the highest form of martyrdom as giving everything for the greater glory of God. To achieve this, one must put oneself into the hands of danger and trust in the keeping of God.

We see an example of this off the west coast of Ireland on Skellig Michael. Skellig Michael rises like the back of a porcupine from the moiling waters of the Atlantic. On a landfall that might have been made especially for the Celtic Christian monks and for martyrs, this was a place of ultimate austerity where the only thing left was faith. To get there one had to set out across that first desert—the sea—and trust one’s life to God’s protection. Once on the island there was no comfort.

Skellig Michael rises some 800 feet above sea level. The early inhabitants cut steps into the bare stone, which led to the open roof of the rock porcupine. There they built beehive cells from bare rock. These would have served as chapels, as well as rugged shelters—there must have been a near-constant wind at that exposed height. Doubtless some would have lived here, but we know little about how they survived.

Apparently even this wasn’t enough extremity for some. A few years ago more signs of human habitation were found above the beehive cells and a little farther into the winds and the weather. Someone had managed to create even more exposure in order to make the place even more daunting. They found a more extreme martyrdom than those who survived clinging to the black rock.

If the island of Iona had become so loud with the babble of chattering voices, then where did Columba go to escape that tumult? A few years back I wrote a novel called The Well of the North Wind in which I ask that very question. I wanted to understand something of the nature of those days on Iona, using my imagination. While I am neither a historian nor an archaeologist, I have a profound love of those times.

Those who know Iona will be aware of the Hermit’s Cell, standing in the midwest of the island. The Hermit’s Cell is close to an area of the island I dearly love, a wild and unconquered part that feels almost Old Testament in character. It is composed of great looming rocks and little glens. During the lovely blue days of early summer, the larks sing here and the orchids grow in profusion. Often there are the coal-black voices of ravens overhead, and when I walk here I think of Old Testament prophets and the ravens that came to them with food.

The name of this part of the island in Gaelic is too difficult for me to pronounce or remember, so I call it the Great Loneliness. To this day at the abbey on Iona, you can be in the midst of conversations with folk from 15 different countries as they argue over the true nature of communion. But walk to the west, to the Great Loneliness, and it feels as though there’s no one between you and America.

Perhaps there was no single hermit at the Hermit’s Cell. Perhaps it was inhabited by different souls at different times, when life over on the east coast, in the white-hot fire of all the arguing and excitement, became too loud. But it surely was a place of retreat. Just beside the Hermit’s Cell is the Well of the North Wind. The one and only thing hermit monks needed was fresh water. It’s both a lovely fact and a lovely metaphor.

We know that there was another place that Columba and the early monks went, but the problem is that the name it was given then—Himba—means little to us now. It derives from the Gaelic for a notched island, but we can only guess which island and where it might have lain in relation to Iona. Some scholars believe it might refer to Oronsay, the tiny islet off Colonsay, with its chapel and grave slabs. Or that it was Canna in the Small Isles west of the port of Mallaig, or even Barra in the Outer Hebrides. All you need is a good amount of imagination to justify your choice.

A few years ago, after my father’s death, I found a thin and seemingly insignificant book in his library. It was self-published, and its pages contained some fairly poor pictures. The book was about a tiny island among what are known as the Garvellachs, a little cluster of islets to the east of the east coast of Mull, not far from the north of the island of Jura and almost immediately due west of the Corryvreckan, the great whirlpool. Here was a holy island that the author believed to have been the place of pilgrimage for Columba, a place established by St. Brendan a generation before Columba first traveled to Iona. This island would have been a day’s journey from Iona and similarly distant from the north coast of Ireland in good weather.

Last year I visited this place on a retreat with a group of friends from our home island south of Oban. Here are the only beehive cells in Scotland; a well, at the landing place, is dedicated to St. Columba. There are tiny inlets named after Brendan and Bridget. As we came to the beehive cells, I looked beyond the well and the landing place to see the ghostly imprints of tiny fields on the last bit of land there. Before I left, I ran up to the island’s highest point and looked down to see a great gully that plunged hundreds of feet to the island’s west side. For me it could mean only one thing with absolute certainty: the notch of that place of pilgrimage and retreat. Columba’s Notch.

A version of this article appears in the print edition under the title “Iona’s desert.”