Most political debate is superficial. Just turn on cable news. Philosophy is for people who want to understand the deep questions. The goal of political philosophy is to determine the standards by which we judge different institutions good or bad, just or unjust. Some people might think they don't have much need of political philosophy: "Who cares about wishy-washy obtuse notions of justice? I'm a pragmatist. I just want to know what works." But this isn't a way of avoiding political philosophy; it's a way of being dogmatic about it. Before we can just do "what works," we have to know what...