It was the moment Matthew Bishop knew he had to write a book: Warren Buffett had just decided, over time, to donate 85 percent of his fortune, most of which would benefit the Bill and Melinda Gates Foundation.

“Two of the richest men in the world at the time, Gates and Buffett, decided to give up their money and talent to helping some of the poorest, most afflicted people on the planet,” Bishop said. “It was clearly something I had to write about at length, and it was the perfect thing for a book. Are they really able to make a difference?”

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The American business editor and New York bureau chief for The Economist, Bishop tried to answer that question before a standing-room-only Master’s Tea at the Jonathan Edwards master’s house on Wednesday afternoon. Bishop spoke for over an hour about his thoughts on celebrity, philanthropy and capitalism, topics that he also covers in his recent co-authored book “Philanthrocapitalism: How the Rich Can Save the World.”

“Some people said its release couldn’t have been worse-timed,” Bishop said. “It came out more or less to the day of the Lehman Brothers collapse. Instead of saving the world, ‘The Rich’ featured in the subtitle have largely been screwing it up.”

Also known as venture philanthropy, philanthrocapitalism involves applying the principles of capitalism to the world of philanthropy. Bishop points to Bill Gates, the former Microsoft chief executive officer, as one of the founders of the modern movement.

Since the days of Andrew Carnegie and John Rockefeller, philanthropy has evolved as the government became more involved in welfare programs and helping the disadvantaged, Bishop said. A century ago, philanthropists donated to causes neglected by a small government whose altruistic scope was limited. Today, philanthropists like Gates and Buffett must invest wisely to make a difference amid a sea of government programs.

Prompted by a student question, Bishop also said celebrity was driving the new philanthropy. Bishop described Angelina Jolie, Bono and Shakira as “celanthropists” — philanthropic celebrities — who he said are emblematic of this trend. They are among the stars using their popularity to communicate serious messages to specific groups of people, and to bring business-minded entrepreneurs into philanthropy.

“Part of that is probably reflecting terrible superficial things,” Bishop said. “But some is understanding mass communications and communicating with younger consumers to actually make a real difference in achieving impact with their giving.”

After a century of governments redistributing wealth from rich to poor, Bishop said, the world has shifted to become a place where governments actively encourage the amassing of wealth. Because of this shift, Bishop said he feels that wealthy individuals have an obligation to be philanthropists.

“I think that is a very good point,” said Mason Marshall ’11, who attended Bishop’s talk. “The rich are rich because of the society they’re in. If they were in a different society, they wouldn’t have those opportunities.”

Erin Schutte ’12 said it was “reassuring” to hear a sunny prognosis for philanthropy given the current bearish economic climate.

“He was very optimistic about the role that philanthropy would play in the world,” Schutte said. “The philanthropic capitalism part is a motivating factor that’s going to initiate the change we need.”