Uri Gneezy and John List are like the anthropologists who spend months in the field studying the people in their native habitats. But in their case they embed themselves in our messy world to try and solve big, difficult problems, such as the gap between rich and poor students and the violence plaguing inner city schools; the real reasons people discriminate; whether women are really less competitive than men; and how to correctly price products and services. Their field experiments show how economic incentives can change outcomes. Their results will change the way we both think about and take action on big and little problems, and force us to rely no longer on assumptions, but upon the evidence of what really works.