Cass Sunstein talks about the ideas in his latest book, Worst-Case Scenarios. How should individuals and societies cope with low-probability events with potentially catastrophic consequences? In this conversation with host Russ Roberts, Sunstein discusses the uselessness of the precautionary principle as a guide to behavior and the psychological challenges we all face in coping with uncertain, risky events. He also speculates why we have chosen politically to treat terrorism and global warming so differently.