I am not superstitious. I don’t believe in magic or miracles, and doubt the existence of things unseen. I’m a cause-and-effect guy.

But I have this sweater.

It was a gift, though I admit receiving it with mixed feelings. My wife picked it up for me at an estate sale and came home and said, “You won’t believe what I found for you.”

“Yes I will,” I said (see opening statement above).

It was a camel-colored cardigan. Ribbed wool, semi-shawl collar, and — its best feature — a matching suede front that made it look like something Gene Kelly would have worn. It appeared to be almost new.

“Try it on,” my wife said.

I thought about this for a second, wondering idly about the most recent condition of the last person to put the sweater on. It was, after all, from an estate sale.

I put it on anyway and I have to admit that not only did it fit perfectly, but it looked good on me, something that isn’t generally true of cardigan sweaters, which tend to make anyone but a model look dumpy. Not this one.

My wife smiled at me. “Thank you,” I said. And then I took off the sweater and draped it over the back of my office chair.

That was more than 20 years ago. I have not put it on again since. But it’s still there, on the back of my chair. It’s behind me right now, as I write this, keeping me company, as it has done year after year, for over two decades.

You’re thinking that I just don’t notice the sweater anymore, that it has become as invisible to me as the legs of my desk. But no, actually. I notice it constantly, and seeing it there on the back of my chair makes me content. Why don’t I ever wear it? Because that is not where it belongs.

The sweater stays where it is because it has become unthinkable to me that it would be anywhere else. It has survived a number of chair replacements, four or five I suppose, and the move to this house 15 years ago. Once or twice I wondered, at one of these turning points, whether I ought to get rid of the sweater.

I never have. Odds are, I never will. The sweater is not a talisman. Nothing bad would happen to me if I somehow lost it, though I cannot fathom how such a thing would happen. The sweater has no special properties, other than staying power. Which turns out to be important.

I’m not superstitious, but I’ll confess to being sentimental. I become attached not just to places and people and events and even things, but to the memories of where I’ve been and what I’ve seen. That sweater and I have been through a lot together. And because my life has been a mostly charmed one — more people should realize this is true for them — I sometimes catch myself thinking of the cardigan as my “lucky” sweater, even though I don’t believe in luck.

The sweater was with me on the day my wife, who was due any minute with our third child, called me from her check-up at Abbot Northwestern Hospital and asked me if I thought we should have a baby that day. This was on a Friday the 13th.

“Absolutely,” I said.

And I was leaning back against the sweater on an afternoon a few years later when an agent in New York called out of the blue and asked me to write what was to be my first a book. The sweater was right there with me when I finished.

Of course, we all travel through life surrounded by objects that have special meaning. Among the things on permanent display in my office are a deer skull found in the windbreak out back, a chunk of the Berlin Wall that a friend picked up for me on the day the wall came down, quite a lot of trout-fishing gear, hundreds of books, a small bolt from a Gemini manned spacecraft that my father worked on, and a Charles Darwin bobble-head doll I received for delivering an Earth Day speech at Indiana State University.

We can all make a list like this, an inventory of inanimate objects that we regard with special affection. They’re not trophies, they’re proof of life. The longer we keep such things, the harder it becomes to let go of them.

Maybe this is part of what people mean when they talk about karma, which usually seems to me like nonsense — unless by karma you mean some kind of comfort zone that follows you everywhere. Whatever you do, everything you have, it all becomes a world you live inside of, a place in your heart and mind that reminds you of what home feels like, no matter where you are.

I am famous in our family for throwing things away. I cannot abide clutter. Whenever something goes missing at our house, the accusatory stares fall on me. “Dad probably threw it away,” are words I have heard often, though it’s rarely true of anything important.

Certainly nothing as important as an old cardigan sweater.

William Souder’s biography of John James Audubon, "Under a Wild Sky," was a finalist for the Pulitzer Prize. His most recent book, a biography of Rachel Carson, was a New York Times Notable Book in 2012 and was also named one of the 25 Best Nonfiction Books of the year. He is currently writing a biography of John Steinbeck, which will be published by Norton in 2019.