Bouncing from idea to idea, creating company after company, Clark has accumulated a personal fortune worth billions. That’s impressive enough. But along the way, Clark also has managed to redefine the culture of American business, helping to transform what had been a cult of the corporation into a new cult of the entrepreneur.

Among contemporary business figures, few inspire more devotion from their followers than Clark. All he has to do is announce a new idea and the talent — as well as the money — comes clamoring for a chance to participate. And why not? Business Week has credited him with having “20/20 foresight.” Journalist Michael Lewis just published an entertaining book about the man, in which Clark emerges as a kind of seer, a seeker and, often as not, finder of what Lewis terms “the new new thing” — “the idea that is a tiny push away from general acceptance and, when it gets that push, will change the world.”

Clark is philosophical about the book, in which he’s not always depicted in a favorable light. In an Oct. 27 article in the San Francisco Chronicle, he says that Lewis draws him “as a little greedy, and I never envisioned myself that way because I’ve shared a lot with the others in all the companies I’ve been involved with.” Elsewhere in the article Clark observes, “It’s very difficult to see myself in print. It’s not a flattering portrayal, but I suppose it’s balanced and reasonably fair.”

That Clark is a genius is beyond dispute. Yet it’s hard not to feel somewhat uneasy about what his talents have wrought. His greatest gift has been an ability to articulate groundbreaking ideas in a way that attracts both start-up capital and technical expertise. The actual execution of those ideas — the mundane tasks of creating a company, meeting a payroll, getting a product to market — has generally been left to others, as Clark rushed off to create his next venture. Lewis calls it capitalism as “conceptual art.”

That’s fine as long as you’re coming up with ideas like computer graphics or Internet browsers. The problem is that the high-tech world is now packed with would-be visionaries hawking their own versions of the “new new thing.” Venture capitalists, terrified of missing out on the next Netscape, are throwing money at ideas that are ill-formed at best, and often downright dubious.

“There is so much money out there that no one has the luxury of actually developing an idea,” a prominent New York venture capitalist, who is currently gambling with $50 million in funds from a major bank, recently told me. “All the market requires now is that you tell a good story.”

Jim Clark hardly seemed destined to be the man who rewrote the rules of American business. His background is pure American Gothic of a particularly nasty nature. Now 55, he grew up in the 1950s in Plainview, Texas, a town known as the home of country singer and sausage king Jimmy Dean and not much else. His mother worked in a doctor’s office and his father performed odd jobs — although the bulk of his energy apparently went into drinking to excess and thinking of creative ways to abuse his wife. After the couple divorced in 1958, his mother supported Clark and his brother and sister on a mere $225 a month.

Clark soon severed his relationship with his father, but he inherited at least some of the man’s ornery attitude. He was suspended from school for setting off a smoke bomb on the band bus. He smuggled a skunk into a school dance. When he was 16, an English teacher scolded him for failing to read “The Rime of the Ancient Mariner.” Clark told her to go to hell. He was suspended and never returned.

Eager to escape Plainview, Clark joined the Navy. Returning to the States after nine months at sea, he took a math test and stunned his instructors by scoring highest in the class. They urged Clark to earn his high school equivalency and go to college. He enrolled in night classes at Tulane University, and eventually gravitated toward computer science, earning a doctorate in the subject. It was during a teaching assignment at the University of Utah that Clark encountered his first high-performance graphics computer, an experience that sparked the ideas that would lead to Silicon Graphics — and a complete reconsideration of exactly what computers are capable of.

Working as an associate professor at Stanford University, Clark designed a computer chip that was able to process 3-D images in real time, allowing engineers to model their designs on a computer screen, saving months of work and thousands of dollars. He dubbed his invention the “Geometry Engine,” hired a handful of his students and, in 1982, created Silicon Graphics Inc., one of the first and most important companies of the new economy. “Jim’s logic was that the world was three-dimensional, and so the computer would have to be, too,” one of Clark’s students recalled. “He thought the right way to interact with machines is the way you interact with the world.”

Along with NASA, Hollywood filmmakers were among the first to see the possibilities of such technology, and Lucas and Spielberg were some of Clark’s first customers. He also began attracting the best engineers in Silicon Valley. But if Clark had a great eye for technology, he still had a lot to learn about business. And he ended up learning it the hard way. To finance Silicon Graphics, Clark sold a 40 percent stake to venture capitalist Glenn Mueller of the Mayfield Fund for a mere $800,000. It took less than a year to burn through the sum. Mueller and his investors bought another chunk of the company, this time for $17 million. Later, Clark and his engineers had to sell even more of their equity, leaving them with an ever smaller piece of what it was obvious would become an extremely profitable pie. Clark burned with resentment.

That feeling was only heightened when Mueller brought in Ed McCracken, a former vice president at Hewlett-Packard, to serve as the company’s CEO. Clark knew he was no manager; fixated on the big picture, it was obvious even to him that he lacked the ability to sweat the myriad details necessary to run a company. But McCracken was as conservative as Clark was mercurial and the two fought bitterly. (“Clark’s friends who did not know Ed McCracken came to believe that the man’s name was Fucking Ed McCracken,” Lewis writes. Always the prankster, Clark also replaced the nameplate on his nemesis’s door with one reading “Ed McMuffin,” a change it took poor Ed three days to notice.)

Silicon Graphics fast became the most successful company in Silicon Valley. Revenues went from the millions to the billions. It went public in 1986 and saw its stock rise from $3 to $30. But although he retained the title of chairman, Clark increasingly found himself frozen out of his own company, marginalized by a board that had no interest in his particular brand of creative destruction. In 1994, he left the company he had created and began to look for something new.

At first, Clark was drawn to interactive television, which had captured the imagination of some of the nation’s largest media conglomerates. He happened to e-mail Marc Andreessen, the 22-year-old software whiz who had developed the Mosaic Web browser while a student at the University of Illinois. Clark initially thought he would lure Andreessen into an interactive TV business. But after talking with the young man, he became convinced that the Internet was the way to go. And thus Netscape Communications Corp. was born.

Soon enough, the valley’s venture capitalists were hovering, looking for an opportunity to buy in. But Clark had learned an important lesson at Silicon Graphics. Eventually, Clark sold a 15 percent stake to John Doerr of Kleiner Perkins for an astonishing $18 million, leaving Clark himself with 25 percent — terms unheard of on Sand Hill Road. Venture firms throughout the valley cursed their bad luck, none more so than Glenn Mueller, the original backer of SGI. Told he would not be permitted to invest in Netscape, Mueller shot himself in the head a week later. It turned out that Mueller suffered from severe paranoia, and was convinced that everyone in the valley was working to put him out of business. The episode served only to enhance the mysterious aura that had come to surround Clark.

That aura was enhanced even more a year later, when Netscape filed papers with the Securities & Exchange Commission to go public. The filing was audacious, to say the least. At the time, venture capitalists generally waited for a firm to show at least four consecutive profitable quarters before peddling it to investors. Netscape had nothing on its balance sheet but red ink. But it had a great story to tell. And apparently, the public was in the mood to listen. On the first day of trading, Netscape shares rose from $6 to $24. Three months later the stock traded at $70. Jim Clark had made many people very rich. And as Netscape’s largest individual shareholder, he became Silicon Valley’s newest billionaire and pioneered the now ubiquitous Internet IPO.

It didn’t take long for Clark to realize that Netscape’s dominance of the browser market wouldn’t last long, not with Bill Gates on the scene. Already, Microsoft’s own Internet browser was whittling away at Netscape’s market share. And because Microsoft’s Windows enjoyed a near monopoly in PC operating systems, it would only gain more, Clark feared. So what did he do? He began looking for new ways to make money.

He soon turned his eye on the U.S. health-care market. In the early 1990s, he had been in a motorcycle wreck that crushed his leg. Later, he was diagnosed with a blood disease that required regular trips to the doctor. In both cases, Clark, like virtually all American health-care consumers, found himself frustrated with the long waits and complicated forms. Why not use the Internet to eliminate paperwork by linking all the health-care players — the doctors, patients, pharmacies, health plans and benefits administrators — to a central depository of information? Clark’s company, dubbed Healtheon, would control that depository and collect a few pennies of each transaction. Considering that the $1.5 trillion health-care sector is the largest component of the U.S. economy, Healtheon could make billions, even if it only handled a fraction of those transactions.

Like most of Clark’s ideas, this too was an audacious notion. Neither Clark nor his engineers claimed to understand the severe problems faced by the byzantine U.S. health-care system. But the idea had a certain elegance to it. It also was a good story. And most important, it belonged to Clark. As a result, venture capitalists who were shut out of Netscape were slavering over the idea.

Healtheon had a rough start. The software was late to the market, and the nation’s health-care companies were less than eager to embrace new technologies. An initial attempt to go public was aborted amid last fall’s stock market swoon. But by February, the markets had recovered and investors had regained their appetite for promising Internet companies that still happened to hemorrhage cash. And so it was that Healtheon saw its share price shoot to $33 and Jim Clark became the first person in the world to create three different multibillion-dollar technology companies.

Healtheon’s future remains murky. With its purchase of Web MD, the company has become a comprehensive source of health-care information, the real money lies in commerce. Yet so far, only a handful of the nation’s large insurance companies have adopted sophisticated computer systems and many still process claims by hand. Most doctors’ offices are even less technically adept. The act of uniting them all in a cohesive Web seems daunting, to say the least.

Clark, characteristically, had little interest in hanging around. “Having articulated the new new thing,” Lewis writes, “Clark intended to return to the important work of teaching his computer to sail his new boat.”

That would be the Hyperion, a 155-foot, $30 million sailboat with a 197-foot mast, designed to be controlled by 25 high-powered Silicon Graphics workstations. Originally conceived as the basis for a new business that would create so-called smart homes whose every function was controlled by computers, the project has obsessed Clark — and baffled those who know him — for years. Eventually, he hopes to be able to control the Hyperion from his living room, via the Internet. That’s some ways off. Last spring, on the boat’s first transatlantic voyage, the on-board computers inexplicably shut down the engine. Unable to fix the glitch while at sea, the crew was forced to complete the journey the old-fashioned way.

Clark, not surprisingly, has shown no willingness to give up. And whether the boat actually will be sailed successfully by a computer seems almost beside the point. Instead, Clark seems drawn to Hyperion precisely because of the impossibility of ever pulling it off. Will he ever do it? Every instinct argues no, that perhaps there are some places where computers and the Internet truly do not belong. On the other hand, considering all that’s happened over the past 18 years, it’s very difficult to bet against Jim Clark.