Take the case of Harold McMaster, an inventor of glass tempering and solar energy devices, and his wife, Helen. The couple lived modestly in Perrysburg, Ohio, while giving hefty grants anonymously in the 1980s to higher education in their state.

After a few years, fund-raisers persuaded them that going public would motivate other potential donors. And that turned their world upside down, Helen McMaster recalled.

Giving became fun again only after they hired a professional screener, McMaster said. Indeed, most big anonymous donors in the Indiana study did so to avoid drawing hordes of fund-raisers.

"If you declare your charities, they are still good," the Quran says in Chapter 2, Verse 271. "But if you keep them anonymous, and give them to the poor, it is better for you and remits more of your sins. God is fully cognizant of everything you do."

According to rules for charity written by the medieval Jewish philosopher Maimonides, charity was better when "the righteous gave secretly and the good poor drew sustenance anonymously."

For Christians, Jesus' advice in the Sermon on the Mount is the key: "When you give alms, sound no trumpet before you, as the hypocrites do in the synagogues and in the streets, that they may be praised by men."

American donors followed that advice more often in the 19th Century, according to Indiana's Dwight Burlingame, the assistant director of the philanthropy center, but for a different reason. Anonymity, he said, enabled people of means and standing to contribute to controversial causes, such as the abolition of slavery, mental health, immigrant aid, sex education or ending white slavery.

Massive giving by Andrew Carnegie, John D. Rockefeller and other industrial titans national and local -- virtually all by name to enhance their reputations -- dominated U.S. giving after the turn of the century.

Burlingame, who helped devise Indiana's study, said anonymous giving probably had declined further among big donors since 1991, when the survey was conducted.

These days, he said, successful fund-raisers press donors harder to give by name because named donors often persuade others to give. For their part, fund-raisers have found that "naming opportunities" are a powerful incentive for recognition-seeking donors.

Frustrated by red tape when he tried to deliver aid to Sept. 11 victims, Budd said, he decided that handing out chain saws and generators directly to Katrina's victims was the only way to go. So he and a volunteer from his dealership, in a second truck carrying 200 gallons of gasoline, drove 17 hours to give away gear donated by Budd, a John Deere dealer and some local Rotary Club allies.

Some Biloxi recipients were suspicious at first, he found, when all he asked was that they pass along the gear to another family in need once they finished with it.

Giving away the truck, he said, came to him after he heard on the radio on the way down that Biloxi had lost lots of firefighting equipment and he saw how flattened the city was.

A brass plaque sits on the corner of his desk. A former boss gave it to him as a hint, Budd said, when he was 28, running the biggest Ford dealership in Virginia, and considerably less modest.

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