New York:
Shortly before the iPad tablet went on sale last year, Steven P. Jobs showed off Apple's latest creation to a small group of journalists. One asked what consumer and market research Apple had done to guide the development of the new product.
"None," Mr. Jobs replied. "It isn't the consumers' job to know what they want."
For years, and across a career, knowing what consumers want has been the self-appointed task of Mr. Jobs, Apple's charismatic co-founder. Though he has not always been right, his string of successes at Apple is uncanny. His biggest user-pleasing hits include the Macintosh, the iMac, iBook, iPod, iPhone and iPad.
But as he takes a medical leave of absence, announced on Monday, the question is: Without him at the helm, can Apple continue its streak of innovation, particularly in an industry where rapid-fire product cycles can make today's leader tomorrow's laggard?
There is no near-term danger. Apple's surging sales and profits have made it the world's most valuable technology company, surpassing Microsoft last year. Apple reported on Tuesday that its profits and sales jumped more than 70 percent in the fourth quarter, exceeding high expectations.
Apple is on a roll, with new models of products in the pipeline. Yet there would be concern, analysts say, if Mr. Jobs does not return full-time to the company, given his unique role in shaping Apple's products.
"Steve Jobs has this extraordinary ability to see into the future and instinctively see what people want," said Michael A. Cusumano, a professor at the Massachusetts Institute of Technology's Sloan School of Management. "He's done that consistently, in a way no one else has."
Mr. Jobs, by all accounts, relies on intuition and his own sense of taste, in decisions ranging from hiring to matters of product design. "Steve is one of the most instinctive people I know," observed Michael Hawley, a computer scientist at M.I.T. who worked for Mr. Jobs at Next, a pioneering but commercially unsuccessful computer company. That was during the period after 1985, when Mr. Jobs left Apple; he returned in 1997.
As the final arbiter on product decisions, Mr. Jobs, colleagues say, is uncompromising. Prototypes and early working products are produced and constantly refined. They are shown not to focus groups or other outsiders, but to Mr. Jobs and a few members of his team.
Three iPhone prototypes were completed over the course of a year. The first two were tossed out, said a former Apple manager, while the third passed muster. The product shipped in June 2007. The iPad tablet, at Mr. Jobs's insistence, relies on only touch-screen navigation -- even though industry analysts said business users, in particular, would want a stylus.
With the iPad tablet, Apple jump-started a product category. But with the iPod (a music and media player) and iPhone (smartphone), Apple moved into markets with many millions of users using rival products, but he gave consumers a much improved experience.
"These are seeing-around-the-corner innovations," said John Kao, an innovation consultant to corporations and governments. "Steve Jobs is totally tuned into what consumers want. But these are not the kind of breakthroughs that market research, where you are asking people's opinions, really help you make."
Regis McKenna, a Silicon Valley investor and marketing consultant, said employees at Apple stores provide the company with a powerful window into user habits and needs, even if it is not conventional market research.
"Steve visits the Apple store in Palo Alto frequently," said Mr. McKenna, a former consultant to Apple.
The design decisions made by Mr. Jobs, Mr. McKenna said, are informed by his grasp of users' desires, technology trends and popular culture. In the end, he added, Apple products also reflect Mr. Jobs's personality.
"Steve's a cool guy and he designs cool products," Mr. McKenna said.
Such skills, analysts say, cannot be easily replaced. "There are lots of creative ideas in any good company, but ultimately choices have to be made," said David B. Yoffie, a professor at the Harvard Business School. "Steve Jobs has made great choices and then refined those. That's a real art, not a science."
Mr. Jobs prides himself on being a leader more than a manager. An important part of his leadership ethos, he has said, is to select lieutenants that share his persistence and passion for the business.
And the people he has recruited have given him plenty of help since he returned to Apple in 1997. During his medical leave, Apple will be led by Timothy D. Cook, the chief operating officer, who Mr. Jobs recruited from Compaq in 1998. Mr. Cook stood in for him during an earlier absence.
Mr. Jobs, who has battled pancreatic cancer and had a liver transplant a year and a half ago, has taken two previous leaves of absence.
"This is a guy who has wrestled the angels to a stop before," said Paul Saffo, a managing director of Discern Analytics, a research firm. "His most lasting creation is the company, not individual products, and you have to believe he has done everything he can to ensure Apple will have a long life."
In a conversation years ago, Mr. Jobs said he was disturbed when he heard young entrepreneurs in Silicon Valley use the term "exit strategy" -- a quick, lucrative sale of a start-up. It was a small ambition, Mr. Jobs said, instead of trying to build companies that last for decades, if not a century or more.
That was a sentiment, Mr. Jobs said, that he shared with his sometime luncheon companion, Andrew S. Grove, then the chief executive of Intel.
"There are builders and traders," Mr. Grove said on Tuesday. "Steve Jobs is a builder."