This book offers an exceptionally impressive, and wide-ranging, set of essays on behaviourally informed approaches to law and regulation in Europe, with particular reference to nudges. In Europe as elsewhere, an important question is drawing increasing attention: what are the ethical limits on nudges? This question is in the background of many of the chapters, and sometimes it emerges in the foreground (chapter 4 by Van Aaken, chapter 13 by Feldman and Lobel, chapter 14 by Alemanno and Sibony). It is on this question that I would like to focus in this Foreword. In free societies, respectful of human dignity and dedicated to the idea of self-government, the issue is a pressing one. My central argument is that at least if they are taken in general or in the abstract, the leading ethical objections lack a great deal of force, and for two different reasons. First , both nudges and choice architecture are inevitable, and it is therefore pointless to wish them away. Second , many nudges, and many forms of choice architecture, are defensible and even required on ethical grounds, whether we care about welfare, autonomy, dignity, self-government, fair distribution, or some other value. Nonetheless, it is true that all government action, including nudges, should face a burden of justifi cation (and sometimes a heavy burden). If the government requires disclosure of information, or establishes particular default rules, it must explain and defend itself. The fact that people retain freedom of choice, and are ultimately permitted to go their own way, does not give public offi cials a kind of license to do whatever they want. If we value democratic self-government, we will be inclined to support nudges and choice architecture that can claim a democratic pedigree and that promote democratic goals. Any democracy has a form of choice architecture that helps defi ne and constitute its own aspirations to self-government.