Why did critical legal studies disappear? Will it reappear? Why does the Federalist Society prosper? Why, and when, do people write books on constitutional law, rather than tort law or antitrust? Why did people laugh at the notion of animal rights, and why do they now laugh less? Why do law professors seem increasingly respectful of textualism and originalism, ideas that produced ridicule and contempt just two decades ago? How do book reviewers choose what books to review? Why has law and economics had such staying power? Academics are generally committed to truth, and they are drawn to ideas that can be shown to be good ones. The most optimistic answer to these questions is that ideas survive because and to the extent that they are t...