In medical school, Paul Farmer found his life’s calling: to cure infectious diseases and to bring the lifesaving tools of modern medicine to those who need them most. Tracy Kidder’s magnificent account shows how one person can make a difference in solving global health problems through a clear-eyed understanding of the interaction of politics, wealth, social systems, and disease. Profound and powerful, takes us from Harvard to Haiti, Peru, Cuba, and Russia as Farmer changes people’s minds through his dedication to the philosophy that “the only real nation is humanity.”