In their 2008 book Nudge: Improving Decisions about Health, Wealth, and Happiness, Richard Thaler and Cass Sunstein use research from psychology and behavioral economics to argue that people suffer from systematic cognitive biases. They propose that policy makers mitigate these biases by framing people's choices in ways that help people act in their own self-interest. Thaler and Sunstein call this approach “libertarian paternalism,” and they market it as “the Real Third Way.” In this essay, I argue that the book is a brilliant contribution to thinking about policy making but that “choice architecture” is not just a solution to the problem of cognitive biases. Rather, it is a means of approaching any kind of policy making. I further argue that policy makers must take externalities into account, even when using choice architecture. Finally, I argue that libertarian paternalism can best be seen as motivated by what Sunstein has celebrated in his work on constitutional theory: a humility about the possibility of policy-maker error embodied in Learned Hand's famous aphorism about the “spirit of liberty” and an attempt to reduce social conflicts by searching for what John Rawls called an “overlapping consensus.”