David Ogilvy, 88, the master advertising man whose success proved you can become rich by never underestimating the intelligence of the American people, died July 21 at his home in France's Loire Valley.

His death was announced in New York by Ogilvy & Mather, the agency he started in 1948 with two staff members and no clients. No specific cause was given.

Mr. Ogilvy put the eye-patched man in his Hathaway Shirt, created Commander Whitehead of the Schweppes soda ads, made Dove soap a major brand by trumpeting how it "creams your skin while you wash."

But his greatest legacy was an approach to advertising that assumed the intelligence of the consumer.

"The consumer isn't a moron; she is your wife," he once wrote. "You insult her intelligence if you assume that a mere slogan and a few vapid adjectives will persuade her to buy anything. She wants all the information you can give her."

Mr. Ogilvy was not necessarily an obvious candidate for success. He was born in West Horsley, England, and he flunked out of Oxford. He went to work in the kitchen of a Paris hotel, then returned to Britain and was hired as a door-to-door salesman for Aga Cookers.

He immigrated to the United States in 1938 and went to work at George Gallup's Audience Research Institute. During the war, he served as second secretary at the British Embassy in Washington. Later, he worked as a farmer in Pennsylvania's Lancaster County, among the Amish.

He was 37 years old when he started his agency. Success was swift. Over the years, his clients included General Foods, Lever Brothers, Shell, Sears, American Express.

He set out his principles in memos for his staff and in three books: "Confessions of an Advertising Man," a bestseller in 1963; "Blood, Brain & Beer," a 1978 memoir; and "Ogilvy on Advertising," five years later.

Mr. Ogilvy believed in the power of words, and his ads were chock full of them. But he took care to write simply.

"I once used the word OBSOLETE in a headline, only to discover that 33 percent of housewives had no idea of what it meant," he wrote. "In another headline, I used the word INEFFABLE, only to discover that I didn't know what it meant myself."

Phil Dusenberry, vice chairman of the ad agency BBDO Worldwide and chairman of its New York office, said Mr. Ogilvy will be remembered for "his ability to build and enhance a brand image over a long period of time."

Dusenberry recalled Ogilvy clients such as Rolls-Royce, for which he once wrote an ad with the headline: "At 60 miles an hour, the loudest noise in this new Rolls-Royce comes from the electric clock."

"He very much wanted to appeal to the intelligence of the reader and viewer by talking up to people rather than talking down to them," Dusenberry said.

"He was not a razzmatazz guy," agreed John Bergin, a colleague in advertising, now retired from the McCann Erickson agency. "It's a tragedy because today, the industry is just razzmatazz. . . . He couldn't abide ads that didn't say, 'This is why you should buy this product.' "

Bergin recalled that Mr. Ogilvy hated music and jingles in ads. Once, when Mr. Ogilvy was abroad, his agency sold a campaign that featured a tune--the classic "pucka-pucka-PUCK-PUCK" of Maxwell House coffee.

Mr. Ogilvy was not impressed. "If I'd known they were doing it, I would have stopped it," he told Bergin.

Mr. Ogilvy retired as chairman in 1973, and moved to Touffou, France. He continued to watch over the agency, however; the volume of his correspondence forced an upgrade of the local post office.

Ogilvy & Mather--now with 359 offices in 100 countries--was sold in 1989 to WPP, a British holding company, for $864 million. At the request of WPP's chief executive, Mr. Ogilvy then served as the holding company's non-executive chairman for three years.

Mr. Ogilvy is survived by his third wife, Herta, and by a son, David, a real estate executive in Greenwich, Conn.