In 1975, Peter Singer made a global impact with his book, Animal Liberation. He's now focused on charity — and how everyone has the obligation not just to give away whatever they can afford, but to get the biggest bang for their buck. The Most Good You Can Do: How Effective Altruism Is Changing Ideas about Living Ethically argues that everybody should give away a substantial amount of income to charities. But there's a word of caution: not all philanthropy is good philanthropy.
Photo: TED Conference