Two mysteries have followed me well into adulthood: Does soaping yourself work underwater, and how come there are so many people out on the street all day, seemingly not working? Having pitched a work, and not a soap, column, I recently attempted to answer the latter.

Because look out your window. Who are these people? At any given hour on any given workday, well, it turns out it's not a workday at all. Not for these hordes roaming free, anyway. By rights our parks and movie theaters and stores should be minor ghost towns between 9 and 5 -- chanced upon by the occasional tourist or late-night bartender but otherwise peaceful. Instead, they're inexplicably packed. I didn't doubt that the packers had sound explanations. I just wanted to hear them.

It occurred to me last night that you can learn as much about a city from what its people don't do as you can from what they do do. So I drove to as many parts of San Francisco as I could and interrupted as much leisure as possible to find out.

"Jeffrey" (some names changed at owner's request), writing a poem in a notebook on Church Street, had quit his California Pizza Kitchen job that morning; he was down to a barista gig now. The poem was about knots. With extreme reluctance he conceded to hailing from Fresno. There was "no love" at his pizza job.

John Spencer, 57, was sipping a large soda near some flowers outside the shopping center on Market Street.

"What do I do? I don't do anything. I'm in hospice. And now I'm having a luxury Coke at Safeway," he said.

Spencer was on his way to a writing class at the AIDS Health Project; he writes poetry. The class will end soon. He also goes to respiratory therapy three times a week, and a support group, and he does genealogical work.

I didn't approach school-age kids or obvious tourists. I didn't approach grown-ups wearing lab coats or swinging hammers. These people are either not meant to be working, or they clearly are working. My methodology was to canvass at different hours of the day and to discount those merely on lunch breaks. Science? No. But revealing all the same.

Just visiting, said the blonde with the cappuccino outside a Starbucks; she passes for native but comes from Belgium. And she's been saddened by the weather. (A believer in temporary solutions, I lied that tomorrow was supposed to be lovely.)

"I get Wednesdays off," said Kim Anderson, 29, an administrative assistant at an architectural firm. She spends them at physical therapy or catching up on errands or doing what she was doing here: sitting and watching the dogs at Duboce Park.

"Alan" sat 20 yards away, but his nose was in a short-story manuscript. Once he was a writer in the multimedia industry, but then he was diagnosed with chronic fatigue syndrome. That was 14 years ago and he's been on disability ever since. There are days when typing is exhausting and walking across the room impossible. Today, however, he was out in the sun.

"If there's been anything good in this, it's that I started writing fiction. Which is actually kind of what I always wanted to do."

There are helpful statistics to shed light on the out-and-about. In 2005, 14 percent of San Franciscans 5 and older reported a disability -- nearly 100,000 people. Over 40,000 people were self-employed. Almost 70,000 were in college or grad school. Stereotypes about the contemporary human condition aside, a great many people don't inhabit cubicles.

John, 41, wasn't in a cubicle when I spoke to him. He runs large servers for a living but is between jobs now. He sees lots of movies at the Metreon and concedes he doesn't work out enough.

Many people I encountered reported variations on the "in-between jobs" line, and it's not just a euphemism. Among the employed are those who will soon be without work, thanks to frictional unemployment, the inevitable periods of joblessness structured into even perfect economies. As of March, about 4 percent of San Francisco's labor force was unemployed altogether -- 17,300 people. On top of those are the self-employed, the partially employed and so on.

Going over my own findings, a surprising number of people had had something job-related happen that very day. A surprising number had called in sick. Claire, who works in quality control at a biotech company, used a vacation day to get a tattoo of a bird. Another woman took the day off to be with her dogs. ("And catch up on errands," she added responsibly.)

"John," who is 18 and was strolling through Yerba Buena Gardens one Thursday morning, laid out his typical itinerary: "Watch the grass grow, get high, hit on the ladies."

How does he pay rent? "If you ask 100 girls for $10, that's $1,000, that's rent," he explained logically.

How does he get them to part with their $10?

"I tell them I can't live without them," he answered, with some disappointment at the caliber of question, as though he'd been asked how many moons our planet has.

Also downtown, there was a pastry cook getting on a bicycle who works weekends. Then a couple of teachers chatting at a bus stop in the Sunset, done with their workdays by 3. Two college students, Jeremiah and Tiera, with no classes that day. Another young man who did his security guard work on weekends. Steve, on Divisadero, carrying a neatly wrapped bag of comic books to his son and extolling the pleasures of running one's own company.

A funny thing about these swarms of daytime layabouts: They are quietly self-reflective swarms. Almost all of them admitted to me that they often wonder about their fellow malingerers. The funny thing is, everyone has an answer for themselves but is baffled by everyone else. Possibly this is like life itself.

"They can't all be writing the Great American Novel," said Joshua, 45, nodding in the direction of everyone else. Joshua recently left a large law firm to work on his own, hence his mid-afternoon workout downtown. "I used to wonder who all these people were. Now I'm one of them."

Raul, 34, works security at Cafe Du Nord when he's not cooking on a line. He used to work construction and "would always wonder how the 9-to-5 people got their errands done." He's concluded that many of them work nights, like he does now.

I thought Pacific Heights would be crawling with the daytime idle. If it is, the crawling happens indoors. And away from the windows. Possibly those mansions require long hours at offices? I drove to the Richmond. "Zhang," leaning against a building, said he works in several restaurants and shops. "Not always," he noted, acknowledging his presence on the side of the building.

Ken, in the Castro, is in his 50s and is a published author ("Emphasis on the 'published,'" he requested. "There are lots of scribblers sitting in coffee houses"). When he's not writing, he lectures, makes calls and so on. At the Main Library, a very tall woman gave a be-quiet face, then said she was out of grad school for the summer. Two young actors chatting at Yerba Buena noted the importance of leaving time for auditions.

Aren't we the country that other countries make fun of for working too much? Even the most assiduous Europeans, the British, work more than three hours less than us per week. Almost half of us get less than seven hours of sleep a night, and it's gotten worse in recent years. Our workaholism has spawned entire walls of self-help books. And yet this parallel universe exists right alongside the work-obsessed one. It looks nice, too, as parallel universes go.

The shameless weekday daytime moviegoer lives in another dimension entirely. Richard Inlander, 63, has been retired three years and loves it. In addition to watching movies, he travels, spends time with his grandchildren and does part-time work for Weight Watchers.

"I don't know how I ever had time for a job," he laughed in front of the Metreon's ticket line.

The cafe crowd is another special subset of the don't-seem-to-be-working population. Ritual Coffee Roasters, in the Mission, is a special subset of that subset. All day it's full and, with the music and the laptop acreage, a particularly San Franciscan mellow industriousness fills the place. I set about grilling the laptoppers.

Ben Long, 40, is a freelance writer and photographer. Sometimes he works out of the house, sometimes out of Ritual.

"People aren't just working here -- they're doing more and more of their non-work, too," he observed. "People play massively multiplayer games, they work on their MySpace pages. It isn't just an extension of the office here, it's an extension of the living room."

Keith Kessler, 38, assumes the other laptoppers are mostly Web designers or students. He himself is a lawyer at a downtown firm. He's been there long enough that he can do legal research or work on a memo from here.

Brandan, 41, was working on an e-mail. But he could've been working. He does technical editing and writing. Margaret Mason, seated nearby, makes a living from her blogs, MightyGirl.com and MightyGoods.com. Her book "No One Cares What You Had for Lunch" was written from this same cafe.

"Face time isn't such a thing anymore," she said. "What people care about now is whether you get the work done."

Sitting next to her was her husband Bryan. He has an actual office -- just didn't feel like going to it today.

Closer to the door sat Shauna, 24.

"I don't work. I'm a trust-fund baby," she said, with a nice mix of self-deprecation and not-too-much self-deprecation. What did she do today? "Got up at noon. Farted around. Made corn on the cob. Went to buy a shirt. Came to Ritual."

Her laptop was open; she was reading about careers in psychology. Why pick a career? I asked. It's a question that asserts itself after several days among those with daytime freedom. If you have a trust fund, I asked, why not keep farting around and making corn on the cob?

"I'm bored."

Chris Colin was a writer-editor at Salon, and before that a busboy, a bread deliverer and a bike messenger, among other things. He's the author of "What Really Happened to the Class of '93," about the lives of his former high school classmates, and co-author of The Blue Pages, a directory of companies rated by their politics and social practices. His writing has appeared in the New York Times, Mother Jones, the New York Observer, McSweeney's Quarterly and several anthologies. He lives in San Francisco.