Recognizing the growing role of behavioural sciences in public policy, this book aims to critically analyse the status and role of behavioural sciences while challenging their ability to provide sufficient evidence to build policy and thus provide valid justifications for these policies. By analysing in detail the paradigmatic example of nudges and highlighting the questions they raise from an ethical, political and legal point of view, the author offers the reader the tools to evaluate nudges and the influence they have on individuals' behaviour. In the process, the book makes a convincing case for a new definition of the ethics of influence.