For the past twenty-five years, two questions have kept my curiosity aroused: What makes poor people poor? And what can they do about their poverty? Because of these infernal questions, I've dozed off during hundreds of long jeep rides with good companions over dusty, potholed roads. I've had thousands of conversations with one-acre farmers with dirt on their hands. We've walked along their patches of ten-foot-high black pepper vines in the central...