I. A Phrase My Grandmother Would Have Known
There is an old phrase from the Ireland my grandmother came out of: a thin place. It names a spot on the earth where the wall between this world and the next has worn thin — a holy well, a ruin, a stretch of shore at a certain hour of the evening. Nobody who used the phrase meant it as a figure of speech. They meant it plainly. Some ground is more permeable than other ground, and if you stand on it, you should expect company.
I have come to believe that some people are thin places too. Not haunted, not troubled — just built with less wall between one thing and another. And once you see it in yourself, you start noticing it everywhere: in the friend who cries at other people’s weddings, in the child who asks a hundred questions a day, in the artist who can’t quite tell you where the idea came from because it arrived already finished, feeling like a memory rather than an invention.
This is an essay about that kind of person. I am one of them. And I want to tell you about the woman who named it for me before I had any language for it at all.
II. Carol
When I was a boy, I asked questions. Not the ordinary kind children ask and then forget. I asked and asked, circled back, asked again, chased an idea down five more corridors before I let it go — if I ever let it go. I found the world of the imagined every bit as real, sometimes more real, than the world in front of me. Grown-ups found this tiring. Other children found it strange. I found it, mostly, embarrassing.
Carol didn’t. Carol was a former nun who had gone on to become a psychologist, and for reasons I still don’t fully understand, she took an interest in a curious, chattering boy who talked too much and imagined too hard. She became my mentor and, in time, one of the people I loved most in this world.
One day, worn down by my own barrage of questions, feeling the familiar sting of having been too much again, I must have looked at her the way children look when they expect to be told to quiet down. Instead she smiled and said, “Jimmy, you ask so many questions because you have permeable membranes.”
I didn’t know what the words meant. I only knew what her face meant. She wasn’t correcting me. She was naming something in me and telling me, in the same breath, that it was all right to have it. The shame I’d been carrying — the sense that my curiosity was a nuisance, a defect, something to apologize for — loosened its grip a little that day, and has been loosening ever since. It took me until adulthood to understand how unnecessary that shame had been in the first place. Carol saw that decades before I did.
Carol has passed now — moved on, as I think of it, to the other room. But I have carried her sentence with me for most of my life without ever finding out where it came from or whether it was true in any way beyond her own kindness and her own good instincts. Then, not long ago, I came across the work of a psychiatrist named Ernest Hartmann, and I sat up in my chair, because there it was: permeable membranes, decades later, with a name and a body of research behind it.
III. What Hartmann Found
Hartmann spent years studying people who suffered from frequent nightmares, and he noticed something curious about them. Their trouble wasn’t only that their dreams were bad. It was that the walls inside their minds, generally, seemed to be thinner than other people’s walls — not just around sleep, but around almost everything: the line between thought and feeling, between self and other, between the past and the present, between the fanciful and the real.
So he built a way of measuring it. He asked people a long series of questions about how they experience the world — whether they can focus on one thing while shutting everything else out, whether they know for certain when they’re awake and when they’re dreaming, whether an idea ever arrives to them already wrapped in a feeling, whether they think of people and situations in clean categories or in shades that blur into one another.
What he found was a real, measurable range of human temperament, running from thick to thin.
At the thick end sits a person with sharp, well-kept boundaries. Thought stays separate from feeling. Sleep and waking are two distinct rooms with a closed door between them. The past is filed and finished. People and ideas sort easily into categories: this and not that, us and them.
At the thin end sits someone quite different. Sensation and idea pour in together, all at once, and sorting it into tidy piles is hard work. A thought rarely shows up alone — it comes trailing a feeling, the way Carol’s sentence came trailing a smile I still remember decades later. The border between waking and dreaming is soft; such a person drifts easily into daydream and has trouble finding the door back out. The past does not stay past — it visits, uninvited and vivid, blended right into the present moment. And the line between what is real and what is imagined can, at times, go faint enough that the imagined feels every bit as urgent as the real.
Hartmann called this trait boundary thinness, and what struck me most, reading his work, was not the theory. It was the recognition. I knew this person. I had been this person my whole life, and someone had told me so, gently, when I was still young enough to need the telling.
IV. Thin Boundaries and the Inner Life
People with thinner boundaries, Hartmann discovered, tend to have more vivid dreams and remember them more often. They are more prone to nightmares, yes — but also to something better than nightmares: what researchers call episodes of total absorption. Moments when a book, a piece of music, a memory, or an idea seizes the whole of a person’s attention so completely that the outside world simply falls away. Time changes shape. Distraction becomes impossible. And, strangely, the thing being attended to starts to feel more real, not less, than ordinary life.
Some people with especially thin boundaries live much of their waking life inside a rich, private, internal world — one so vivid that it can feel, briefly, indistinguishable from the world everyone else is standing in.
I recognized every bit of this. I was the boy who found an imagined conversation more compelling than the real one happening in the room, who could vanish into a story or a daydream so thoroughly that someone had to say my name twice to bring me back. I did not think of this as unusual until other people told me, in one way or another, that it was. Carol was the only person who ever told me it was unusual and good.
And here is the detail that stopped me cold when I first read it: Hartmann found that art and music students scored, on average, thinner than the general population. The very trait that made me an inconvenient child at the dinner table — too many questions, too much imagination, too little patience for the literal — turns out to be more common among the people who spend their lives making things.
V. The Poets Already Knew
Here is what surprised me most as I sat with all this. Hartmann was not the first to notice any of it. Poets had been describing the very same thing two hundred years earlier — they simply didn’t have a clinical name for it.
John Keats, writing to his brothers when he was twenty-two, tried to describe what made Shakespeare Shakespeare. He landed on a phrase he called Negative Capability — the ability to sit inside uncertainty and doubt without grasping after a tidy answer. That is a thick-boundaried person’s nightmare and a thin-boundaried person’s native climate. Keats went further in another letter, saying the poet “has no self,” that he can pour himself into a sparrow outside the window and peck about in the gravel right along with it. Read that today and it sounds like someone describing, four generations before the questionnaire existed, exactly what it feels like to have very little wall between yourself and the rest of the world.
Samuel Taylor Coleridge, Keats’s older contemporary, coined a strange word for the same thing: esemplastic, meaning “shaped into one.” He used it to describe the imagination’s power to dissolve separate things and melt them into a single new thing. That is not so different from what happens when a memory and a present moment blend together without asking permission, or when a feeling arrives to you already wearing the shape of a physical object — a cracked heel, a broken piano, a streetlight that is too bright. The Romantics called this imagination. Hartmann, without ever having read a line of Coleridge as far as I know, ended up measuring the same thing with a questionnaire.
And then there is William Wordsworth, who wrote that we come into the world “trailing clouds of glory,” and that childhood is soaked in a kind of visionary brightness most of us lose as we grow older. He asked, achingly, “Whither is fled the visionary gleam?” For two centuries readers took that as a poem about the sadness of growing up. But it reads differently once you know that thin boundaries, on average, do thicken with age — that most people’s walls harden as they mature, while a smaller number of people keep something of that early permeability their whole lives. Wordsworth was not just being wistful. He may have been describing something real: most people lose the gleam, and a few simply don’t.
I find this enormously comforting. It means Carol and Hartmann and Keats and Wordsworth were all, in their own centuries and their own languages, pointing at the same small miracle: some people keep more of childhood’s brightness than others, and that is not a flaw to grow out of. It may be the very thing that makes a person a writer, a painter, a musician — or just someone who never stopped asking questions at the dinner table.
VI. A Question Worth Asking
This is what I keep circling back to, and the question this essay wants to leave you with rather than answer completely: is there a real connection between thin boundaries and creativity?
I don’t think the connection is an accident, and I don’t think it’s flattering in a simple way, either. A person with thin boundaries is, almost by definition, someone for whom things blend that other people keep separate — memory and imagination, feeling and thought, the dead and the living, the self and the person across the table. That blending is exhausting. It is also, I suspect, very close to the raw material of art. You cannot write a character from the inside, or make a metaphor that actually surprises someone, or paint a color that feels like grief, unless something in you is willing to let the borders go soft for a while.
Carol didn’t need a questionnaire to see this in me. She just watched a boy ask too many questions and understood, faster than I ever could have, what that habit was actually made of. She gave me the gift of a name for something I had only ever experienced as a flaw. It took Hartmann’s research, decades later, to tell me she had been right all along — and to suggest that what she saw in me might be worth more than either of us knew.
I no longer feel any embarrassment about my permeable membranes. I think of them now the way Carol seemed to, all those years ago: not as a defect to manage, but as a kind of instrument — one that happens to be a little more finely strung than most, and that, if you let it, will pick up sounds other people miss entirely.
— James Mulhern