America has long struggled over pain. Liberals "understand" your pain while conservatives say "grin-and-bear-it." Such political stances and today's debates over who is in pain, who feels another's pain and what relief is deserved continue to form new chapters in America's history of pain. In his new book, "Pain: A Political History," Keith Wailoo, vice dean of Princeton University's Woodrow Wilson School, explores the political pain divide between liberals and conservatives, tracing the development of pain theories in politics, medicine and law as well as legislative and social quarrels over the morality and economics of relief. We sat down with Wailoo and asked him a few questions about his new book.