Abstract: What institutional arrangements should a well-functioning constitutional democracy have? Most of the relevant literatures in law, political science, political theory, and economics address this question by discussing institutional design writ large. In this book, Adrian Vermeule moves beyond these debates, changing the focus to institutional design writ small. In established constitutional polities, Vermeule argues that law can and should - and to some extent already does - provide mechanisms of democracy: a repertoire of small-scale institutional devices and innovations that can have surprisingly large effects, promoting democratic values of impartial, accountable and deliberative government. Examples include legal rules that promote impartiality by depriving officials of the information they need to act in self-interested ways; voting rules that create the right kind and amount of accountability for political officials and judges; and legislative rules that structure deliberation, in part by adjusting the conditions under which deliberation occurs transparently or instead secretly. Drawing upon a range of social science tools from economics, political science, and other disciplines, Vermeule carefully describes the mechanisms of democracy and indicates the conditions under which they can succeed.