Weeks have elapsed, and I’m still trying to figure out what happened when I visited the ­Matisse Chapel in Vence, France — why I responded as I did. Mystified, I keep coming back to the obvious: I wasn’t prepared.

The only strange part is, I thought I was.

We were on vacation — two adults, two kids, eight pieces of carry-on luggage. We were lucky, obviously, to be traveling together in Europe . . . a dream. But it had already been a long morning: an early taxi, two airports, one plane, a rental car, and it wasn’t yet 2 p.m. We had found our way to the Airbnb in the kind of afternoon heat that leaves dogs whimpering in the shade. A swimming pool beckoned.

“Okay,” said Jo. “Let’s go.”

“Wait, what? Go where?” my daughter said.

We had failed — and not by accident — to tell the kids that, having finally arrived at our destination, we were now going to get back in the car and drive to a small chapel to see some pretty stained-glass windows. That felt cruel.

Yet they didn’t revolt. Too tired and listless, perhaps, and too respectful of their mom (if I had announced it? Instant insurrection!), they grumbled a bit as they got in the car but were mostly compliant.

We promised ice cream afterward and told them the truth: The chapel was just five minutes away. After 4 p.m., it would close until the day we departed. Now, therefore, was the only chance we had. “Also, as you know, Dad really, really loves Matisse.” (Two muffled sighs from the back seat.)

I had never been to Vence, a hilltop town half an hour from Nice in the South of France. I had always wanted to, mainly because of the Matisse Chapel (more formally known as La Chapelle du Rosaire). Matisse spent four years on the project near the end of his life, when he was in his late 70s. He collaborated with two Dominican friars and some nuns. One of those nuns, Sister Jacques-Marie, had, in an earlier life, been Matisse’s nurse, helping him convalesce from cancer surgery.

I’d once read and reviewed a book about the chapel. I’d seen pictures of it, inside and out. I’d heard from others who had been there. I thought I knew what I was going to see.

How, then, was I taken off-guard?

Well, it can happen, of course. You’re tired. You’re hungry. You’re exhausted by travel, by family dynamics, by the brittle tedium of being yourself in an unfamiliar place. Maybe, like me, you’ve been spending too much time in the frictionless world of televised sports, news feeds and social media, swimming in images, none of them more meaningful, more adhesive than the others.

Then, suddenly, you’re jolted awake. You’re in a real place. It’s a particular time of day. Particular currents of air, with particular levels of humidity, are caressing your skin. Particular smells . . .

You’re not necessarily conscious of any of it. But, after all, you’re an animal, a sentient being: Put yourself in it and the physical world has its way with you.

Did I mention I was unprepared?

We paid the admission at a desk in the adjoining building. Confused, I went the wrong way, up the stairs instead of down. “No, Dad! It’s this way!” called my son. (Always setting me straight, that boy. Bless his good heart.)

We entered the chapel, at which point two things happened in quick succession. First, I was overwhelmed by waves of liquid, colored light. Yellow, blue and green. Those words make them sound distinct, but they were one pulsing phenomenon, indivisible. My eyes were absolutely awash in color. The intensity was astounding.

Then, so hard upon the first that it may not make sense to separate them, I was just . . . overwhelmed. All of me. Me, with all my history.

A giant wave of emotion flowed through me. I felt as you do when you’ve lost control in the surf and you’re tumbling around underwater, not knowing which side is up, and you can only wait for the upheaval to end. It was not euphoria I felt. It was not sadness. It was not self-pity or nostalgia. Nor was it religious insight, or a feeling of oneness with all humankind. It was just pure, uncontained emotion.

I could not and cannot make sense of it. I felt sure I was about to sob, heavily — that I would fail to control myself.

But of course, I’m male — 46 years of conditioning — so I did. I moved quickly away from the others, avoiding eye contact — not just with them, but also with the colored glass, in case it triggered a second wave. A tear skittered down my cheek and was jerkily wiped away. I took a seat.

The kids, I sensed, had seen something was up; they sweetly kept their distance. I looked at the white tiles, the altar, the chasuble, Matisse’s stripped-down, rudely artless drawings for the Stations of the Cross, and then at all the smaller details of placement and spacing you fail to grasp in photographs. And within a minute or two, I was well enough defended to take it all in more equably.

Honestly, this sort of thing doesn’t happen to me. I’m an art critic. I see a lot of art and, yes, my responses are often emotional. I get excited, I’m moved, I’m amazed. But I am seldom ever undone.

What was that about?

Obviously I am not the first person to have such an experience. Stendhal, the great French novelist, who famously defined beauty as “nothing other than the promise of happiness” (adding that “it should always be unforeseen happiness”), wrote about an experience he had in the Basilica of Santa Croce in Florence. Santa Croce is where Machiavelli, Galileo and Michelangelo are buried. The sheer weight of those names, combined with the beauty of the church, the fact of being in Florence, and no doubt his blood-sugar levels, all contributed to Stendhal’s susceptibility:

“I was in a sort of ecstasy,” he wrote in 1817. “I reached the point where one encounters celestial sensations. . . . Everything spoke so vividly to my soul. . . . I had palpitations of the heart. . . . Life was drained from me. I walked with the fear of falling.”

In the late 1970s, an Italian psychiatrist, Graziella Magherini, studied more than 100 people who had admitted themselves to Florence’s Santa Maria Nuova Hospital (where she worked) after experiencing rapid heartbeat, dizziness, confusion and, in some cases, hallucinations. In each case, their condition had been triggered by being exposed to objects or phenomena of great beauty, usually during a cultural “pilgrimage” of some kind.

In her 1989 book, “La sindroma di Stendhal,” Magherini gave the condition a name — Stendhal Syndrome. And although it is not listed in the Diagnostic and Statistical Manual of Mental Disorders, it has general currency and was popularized in “The Stendhal Syndrome,” a 1996 Italian thriller starring Asia Argento, also set in Florence.

All of which is fascinating. But I don’t honestly feel that my experience in the Matisse Chapel had anything to do with thrillers or “syndromes,” or even with Stendhal’s “palpitations of the heart.”

I wouldn’t claim so much. I feel no urge to label the experience, or otherwise explain it, whether in religious, medical or art historical terms.

All I know is that it happened, that it was the strongest dose of beauty I’ve experienced in a very long time, and that in my life — my short time on this Earth — it mattered. I couldn’t be more grateful.