In almost every corner of our private and public lives we rely on experts to advise us. This important species of labor is getting increasing attention from economists, who are beginning to learn how to apply their tools and assumptions to the problem of expertise. Under what conditions of supply and demand are experts likely to give us good advice? When is expert failure more likely? Do entrepreneurs challenge existing expertise? Are they experts themselves? And if economists are themselves experts, what happens when we turn the skeptical gaze of economic theory on the economist themselves?...