Our goal in this chapter is to draw on empirical work about preference formation and welfare to propose a distinctive form of paternalism, libertarian in spirit, one that should be acceptable to those who are firmly committed to freedom of choice on grounds of either autonomy or welfare. Indeed, we urge that a kind of ‘libertarian paternalism’ provides a basis for both understanding and rethinking many social practices, including those that deal with worker welfare, consumer protection, and the family.