In Justice, Sandel reveals the philosophical roots of contemporary cultural and political debates—and would Kant have defended Bill Clinton during Lewinsky-gate?

What drew you to philosophy?

I'd always been interested in politics, and after college, I thought I'd spend a term reading my way through the history of political philosophy and maybe run for office. But figuring out the meaning of justice, freedom, equality and democracy took longer than I anticipated. I still haven't been able to disentangle myself from these questions.

How can familiarity with these timeless philosophical debates assist us in decision making? (A rather utilitarian question, I suppose!)

Every time we make a decision with moral implications—in our personal lives or in politics—we live out some answer to these great philosophical questions. Is torture ever justified? Is lying always wrong? Is affirmative action just? Is the free market fair? We can't answer these questions without taking sides in philosophical debates that have been going on for a long time. Thinking hard about these ideas can help us better understand the moral choices we face in everyday life.

Your book is completely free of cant, but still rigorous. What do you think accounts for some philosophers' dependence on jargon and impenetrable language?

I don't think philosophy should be seen as a medicine that is good for you but hard to choke down. My goal was to bring out the excitement of moral and political philosophy—to make it accessible and inviting without cheating the ideas. Some branches of philosophy are technical and remote from everyday experiences. But political philosophy is about how we think and act as citizens. It needs to reach beyond the academy and connect with the experience of ordinary citizens.

Your class at Harvard is phenomenally popular. How do you account for its appeal?

The course challenges students to figure out what they believe and why. It is not only about famous thinkers of the past; it is also a journey of self-exploration. This journey is exhilarating but also risky, because you can't be sure where it will lead. I hope the book captures the same sense of moral exploration, including the unpredictability and fun. I'm eager to see how the book's readers will use a free, interactive Web site we are creating, at www.JusticeHarvard.org. It will enable readers to watch videos of the course and participate in a global, online discussion of the issues.

What's next for you?

My next project is a book on the moral limits of markets. Are there some things that money can't buy, or shouldn't? It builds on some of the topics in the book—the ethics of outsourcing military service to private military contractors, and the ethics of paid pregnancy, or surrogate motherhood.