题目内容：
It all began with a stop at a red light. Kevin Salwen, a writer and entrepreneur in Atlanta, was driving his14-year-old daughter, Hannah, back from a sleepover in 2006. While waiting at a traffic light, they saw a black Mercedes coupe on one side and a homeless man begging for food on the other.“Dad, if that man had a less nice car, that man there could have a meal,” Hannah protested. The light changed and they drove on, but Hannah was too young to be reasonable．She pestered her parents about inequity, insisting that she wanted to do something. “What do you want to do?” her mom responded. “Sell our house?”
Warning! Never suggest a grand gesture to an idealistic teenager. Hannah seized upon the idea of selling the luxurious family home and donating half the proceeds to charity, while using the other half to buy a more modest replacement home.
Eventually, that's what the family did. The project—crazy, impetuous and utterly inspiring—is chronicled in a book by father and daughter scheduled to be published next month: The Power of Half. It's a book that，frankly, I'd be nervous about leaving around where my own teenage kids might find it. An impressionable child reads this, and the next thing you know your whole family is out on the street.
In fact, the Salwens' experience confirms the selfish pleasures of selflessness. Mr. Salwen and his wife，Joan, had always assumed that their kids would be better off in a bigger house. But after they downsized, there was much less space to retreat to, so the family members spent more time around each other. ①A smaller house unexpectedly turned out to be a more family-friendly house.
One reason for that togetherness was the complex process of deciding how to spend the money. The Salwens researched causes and charities, finally settling on the Hunger Project, a New York City-based international development organization that has a good record of tackling global poverty.
The Salwens' initiative hasn't gone entirely smoothly．Hannah promptly won over her parents, but her younger brother, Joe, was a red-blooded American boy to whom it wasn't intuitively obvious that life would improve by moving into a smaller house and giving money to poor people. ② Outvoted and outmaneuvered, Joe gamely went along.
The Salwens also are troubled that some people are reacting negatively, to their project, seeing them as showoffs. Or that people are protesting giving to Ghana when there are so many needy Americans.
Still, they have inspired some people. The people who sold the Salwens their new home were so impressed that they committed $ 100,000 to the project. And one of Hannah's closest friends, Blaise，pledged half of her baby-sitting savings to an environmental charity.
In writing the book, the Salwens say, the aim wasn't actually to get people to sell their houses. They realize that few people are quite that crazy．Rather, the aim was to encourage people to step off the treadmill of accumulation, to define t
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