I once watched a man die inside a pair of parentheses.

Not a metaphor. He was a trader, thirty-seven years old, sitting in front of his screen for fourteen hours, waiting for an order to execute. The buy price was already set, but he hadn't filled in the sell half. He said he was waiting for "the right moment." Later they found he'd had a brainstem hemorrhage. When he collapsed onto the keyboard, his right index finger was still resting beside the Enter key.

His widow asked me: What was he waiting for?

I said I didn't know.

There's a species of sea squirt that has a brain when it's young. It swims, searches for a place to settle. Once it finds one, it attaches itself to a rock and then eats its own brain.

Many people think this is a metaphor.

It isn't.

Adler spoke of something he called the "arc closure reflex." He invented the term but never wrote it down.

I heard about it from his son. Adler died in 1973 in a clinic in Buenos Aires, heart failure. His son said that in the three months before his death, his father had been obsessed with one question: Why can't humans tolerate incompleteness?

A song that stops on the second-to-last note—you wait. A sentence that doesn't finish

Did you feel that just now?

That forward lean. Your muscles prepared a movement. Eyes shifting right, or lips parting slightly. Ready to catch the next word.

That's the arc closure reflex.

It's faster than thought, earlier than pain. It doesn't go through you.

I once worked in a neuroscience lab for three months. What we did was simple: show people an open parenthesis, then measure their brainwaves.

An open parenthesis. That's it.

The subjects' brows would twitch—that was the frontal cortex firing. They couldn't say what they were expecting, but their bodies knew: something had opened, and it must be closed.

After the experiment, we asked subjects to describe how they felt. Most said "nothing." One woman said "like a door left ajar." One boy said "like someone inhaled but didn't speak."

And one old man, seventy-nine, said: "Like being in debt."

Debt.

I've thought about that word often since.

A breath is a debt: you inhale, alveoli expand, oxygen enters the blood. But until you exhale, the transaction isn't complete. Your body knows. Your diaphragm knows. So you exhale, the debt is cleared, the ledger balanced.

But then you inhale again.

You're always borrowing, always repaying.

Adler wrote a set of notes that his son later burned. His son said it was his father's dying wish. But he told me some of what was in them.

Adler believed that all human behavior—all of it—could be reduced to the arc closure reflex.

Love is an arc. You see a person, your nervous system opens a parenthesis. Then you spend the rest of your life looking for the closing one. Sometimes you find it, sometimes that person dies, sometimes you realize there was never a closing parenthesis at all—you drew the opening one yourself.

But your body doesn't care. It only knows it must close.

Ponzi's granddaughter lives in Austin, runs a shop selling handmade soap. I interviewed her once.

She said her grandfather wasn't a con man.

"He just discovered the human operating system," she said. "People need to believe there's something coming next. You give them a promise, and their brains fill in the details themselves. You don't have to do anything."

Her soap smelled like lavender and old newspapers. I bought a bar. I still haven't used it.

I know a programmer who spent two years studying how machines learn to write code.

She discovered something strange.

The first thing machines learn isn't variables, isn't functions, isn't logic. It's parentheses.

"The part that differentiates first," she said, "does only one thing: make sure what opens gets closed. You can delete every other capability, leave just this one, and it still works. It will fix every unmatched parenthesis in the world."

She was laughing when she said this, but her eyes weren't.

I asked her: What does this mean?

She said: "It means closure is primary. Earlier than meaning. A system can understand nothing at all, but it will know when something hasn't ended."

She paused, then said: "Maybe we're the same way."

Maybe we're the same way.

Have you ever thought that everything you do—getting up, drinking water, answering messages, loving someone, hating someone, having children, writing a will—

Maybe none of it is because you "want" to.

Maybe it's because somewhere, somewhere you can't reach, there's a parenthesis that needs to be closed.

Adler's son is eighty-four now, living in a nursing home. The last time I saw him was three years ago.

He said his father spent his final years searching for "the primordial opening parenthesis." The first thing that opened but never closed.

"He thought it was birth," the old man said. "Then he thought it was the first breath, the first time the eyes opened. Later he thought it was the moment the first organic molecule formed."

"Did he find it?"

The old man laughed. His teeth were all gone, his lips collapsed inward, like a flattened parenthesis.

"Before he died, he said one thing to me," the old man said. "He said: 'Maybe there is no opening parenthesis. Maybe there never was a beginning. Only closure. Only our instinct that things should close.'"

I'm not sure I understand that sentence.

But sometimes, late at night, I wake up suddenly, heart racing, as if waiting for something to happen.

I know what it is.

It's my body checking: Is the ledger balanced. Is the breath complete. Is there an arc today that hasn't closed.

That man who died in front of his trading screen—his order finally executed. The buy half he'd placed was automatically held by the system for three years, then sold by his estate executor.

Four hundred percent profit.

His widow took the money, quit her job, and went to Iceland to see the Northern Lights.

She sent me a photo: green light curving across the sky, like a half-written word.

She said: I closed the arc for him.

I didn't reply.

When the sea squirt eats its own brain, it doesn't feel pain.

Its nervous system is too simple—no pain pathways. It just executes a program: find a foothold, attach, digest unnecessary parts.

Unnecessary parts.

Sometimes I think maybe our consciousness is an unnecessary part too. Maybe what's really running is just that program checking for parentheses. We think we're thinking, choosing, deciding, but really we're just watching. Watching that program run itself.

Watching it find an opening, then spend a lifetime looking for the close.

Adler's notes supposedly contained this line:

"Every living moment is an overdraft. You use your future self to guarantee your present self. You call this hope."

I don't know if he really wrote that. Maybe his son made it up. Maybe I'm misremembering.

It doesn't matter.

What matters is that as you read this, somewhere in your body is already waiting for this text to end.

Not because you're bored.

Because it began.

At four in the morning, I sometimes go down to the convenience store to buy cigarettes. The cashier is a woman in her fifties, deep lines around her mouth. She always uses the same phrase when I check out:

"Take care."

Once I asked her: Why do you always say that?

She looked at me as if she didn't understand the question. Then she said:

"If I don't say it, the sentence isn't finished."

She placed my change in my palm. The coins were cold.