THE house is off-limits to children, and adults are asked to sign a waiver when they enter. The main concern is the concrete floor, which rises and falls like the surface of a vast, bumpy chocolate chip cookie.

But, for Arakawa, 71, an artist who designed the house with his wife, Madeline Gins, the floor is a delight, as well as a proving ground.

As he scampered across it with youthful enthusiasm on a Friday evening in March, he compared himself to the first man to walk on the moon. “If Neil Armstrong were here, he would say, ‘This is even better!’ ”

Then Ms. Gins, 66, began holding forth about the health benefits of the house, officially called Bioscleave House (Lifespan Extending Villa). Its architecture makes people use their bodies in unexpected ways to maintain equilibrium, and that, she said, will stimulate their immune systems.

“They ought to build hospitals like this,” she said.

A reporter, who thinks they should never, ever build hospitals like this, tried to go with the flow. Like the undulating floor, Arakawa and Gins, as they are known professionally, tend to throw people off balance.

In 45 years of working together as artists, poets and architects, they have developed an arcane philosophy of life and art, a theory they call reversible destiny. Essentially, they have made it their mission — in treatises, paintings, books and now built projects like this one — to outlaw aging and its consequences.

“It’s immoral that people have to die,” Ms. Gins explained.

The house on Long Island, which cost more than $2 million to build, is their first completed architectural work in the United States — and, as they see it, a turning point in their campaign to defeat mortality.

The house, which is still unoccupied, was commissioned in the late 1990s by a friend who sold the property to an anonymous group of investors after the project dragged on and costs mounted. But it is ready, Arakawa and Ms. Gins said, to begin rejuvenating whoever moves in.

In addition to the floor, which threatens to send the un-sure-footed hurtling into the sunken kitchen at the center of the house, the design features walls painted, somewhat disorientingly, in about 40 colors; multiple levels meant to induce the sensation of being in two spaces at once; windows at varying heights; oddly angled light switches and outlets; and an open flow of traffic, unhindered by interior doors or their adjunct, privacy.

All of it is meant to keep the occupants on guard. Comfort, the thinking goes, is a precursor to death; the house is meant to lead its users into a perpetually “tentative” relationship with their surroundings, and thereby keep them young.

The architect Steven Holl, who has known the couple for at least 15 years, said their architecture is intended to evoke a youthful sense of wonder. “It has to do with the idea that you’re only as old as you think you are,” he said.

For Arakawa, reversible destiny is about more than just a state of mind. By way of example, he described the experience of elderly residents of a building in Mitaka, Japan, that the couple recently designed. Having to navigate a treacherous environment — in some cases by moving “like a snake” across the floor — has, in fact, boosted their immune systems, he claimed. “Three, four months later, they say, ‘You’re so right, I’m so healthy now!’ ”

Like many of Arakawa and Gins’s assertions, it’s hard to know just how seriously this one is meant to be taken. Even those closest to the couple disagree about what they really believe.

Don Ihde, a professor of the philosophy of science and technology at Stony Brook University and a friend of the couple, described them as provocateurs. Their work “makes people think through what they wouldn’t normally think through,” he said.

(As if to prove that point, Professor Ihde has written a paper speculating about how his cat would feel in the Bioscleave House, which he will present on Saturday at the Second International Arakawa + Gins Architecture + Philosophy Conference in Philadelphia, subtitled “Declaration of the Right Not to Die” and sponsored in part by the English department at the University of Pennsylvania.)

“Most people who interpret their work take it as metaphorical,” Professor Ihde added.

Lawrence Marek, a Manhattan architect who helped steer the house through the construction process, disagreed. “Arakawa does believe that if you build things the way he says to build them, life will be prolonged,” he said. “I don’t know if it will or not.” But, he added, “the house has a way of making people happy — it’s a feeling you don’t get from many buildings — and we should be studying how that happens.”

ARAKAWA, who dropped his first name more than 40 years ago, grew up in Nagoya, Japan, studied medicine and art in Tokyo, and moved to New York in 1961, when he was in his 20s. In his pocket, he said, were $14 and the phone number of Marcel Duchamp, who was then living in Greenwich Village. Duchamp, he said, became his patron.

Two years later he enrolled in art school in Brooklyn (for the visa, he said, not the education). There, he met Ms. Gins, a fellow student, who had grown up on Long Island. At the time, she said, “I was deeply alienated from society, which I didn’t see as having any answers.”

Within days they had become a couple and begun making art together. Over the next several decades, living in a loft building on Houston Street, they produced a body of work that includes poetry, philosophy, paintings and conceptual art. From the start, Ms. Gins said, the central theme of their work was “how to reverse the downhill course of human life.”

One of their first built architectural projects, a park in central Japan called “Site of Reversible Destiny,” was completed in 1995. Made up of acres of warped surfaces, it offers visitors advice, in a handout leaflet, like “Instead of being fearful of losing your balance, look forward to it.” (Several people who are said to have broken bones there might wish the name of the park were literally true.)

In 1997 the SoHo branch of the Guggenheim Museum put on a retrospective of the couple’s works. Roberta Smith, writing in The New York Times, noted that “their philosophical or linguistic puzzles can stretch the mind in briefly pleasant ways,” but did not applaud their efforts to build real-world buildings: “Theoretical follies, one of the plagues of contemporary architecture, have their place, and it’s on paper,” she wrote.

For the couple, though, “one building is worth a decade of theoretical exploration,” Ms. Gins said. In 1998 they won a competition, sponsored by the city of Tokyo, to build a vast housing project on 75 acres of landfill. The project was never realized, but a group of supporters in Tokyo arranged to build nine loft-style units, which in many ways resemble the house in East Hampton. More recently, they said, they have been trying to find backers — an effort that has included failed overtures to Russian oil billionaires — for a reversible destiny hotel.

The East Hampton house grew out of the couple’s friendship with an Italian artist named Vincenzo Agnetti, who died in 1981, and his longtime partner, Angela Gallmann. In 1998 Ms. Gallmann, who owned a small post-and-beam house in East Hampton, commissioned them to build an addition that would explore their reversible destiny theory. Soon they had produced elaborate models of a structure in which the ceiling sometimes swooped down to meet the floor.

Even when the couple greatly simplified the plans, finding someone to build it was tricky. “One contractor said he could build the addition for $1.5 million, and one contractor said he could build it for $385,000,” Ms. Gins said. “Guess which one she chose?”

But costs soon increased sharply and Ms. Gallmann abandoned the project. Her daughters had “thought she was insane for working with us,” Ms. Gins said. (Attempts to contact Ms. Gallmann were unsuccessful.)

For a time, it appeared the shell (connected by a hallway to the original cottage) would be torn down. But last year, according to Arakawa and Gins, a group of professors came forward with about $1.25 million to buy the house from Ms. Gallmann and another $1 million or so to complete it.

Arakawa and Ms. Gins won’t say who the buyers are or how they plan to use the house. David Schwartz, a partner in the Manhattan law firm Duval & Stachenfeld and a lawyer for the buyers (who are listed as Professors Group LLC in property records), said he was “not at liberty to say anything” about his clients.

The finished house consists of four rectangular rooms surrounding a free-form living space. The walls are made of various materials including metal and translucent polycarbonate, which admits a gentle light; the floor is made in a traditional Japanese style, using hardened soil, here mixed with a little cement. For those who aren’t especially sure-footed, there are a dozen brightly colored metal poles to grab on to.

The absence of internal doors creates a dramatic flow — and seemingly insoluble privacy problems. “You make your own privacy,” Ms. Gins said, cryptically. In fact, there are hooks in the ceiling, and someday the house could be festooned with curtains or other dividers.

Arakawa and Gins persuaded companies to donate what they said were hundreds of thousands of dollars’ worth of materials and products to the house.

George Bishop, president of Get Real Surfaces, in Poughkeepsie, N.Y., which fabricated counters, tabletops and an elaborate bathtub to the couple’s specifications, charged about a tenth of the usual cost, he said, largely because he was so taken with the couple. “They have the enthusiasm of 10-year-olds at a birthday party,” he said.

Part of their appeal, certainly, has to do with their unwavering conviction. Ms. Gins speaks passionately and fluidly about their work, while Arakawa, whose heavy accent is sometimes hard to decipher, tells charming if immodest anecdotes about the couple’s triumphs. According to him, they have educated physicists about physics, doctors about medicine and painters about art. (In one Arakawa story, de Kooning and Rothko are bowled over by his brilliant observations on color.)

Now Arakawa and Gins are determined to conquer architecture. “After this, Gehry, Rem Koolhaas — boring,” Ms. Gins said.

“We should win a Nobel Prize for this,” Arakawa said. Asked if her husband was serious, Ms. Gins replied, “Of course he is.”

* By FRED A. BERNSTEIN (East Hampton, N.Y.Additional reporting by Zahra Sethna.)