After the so-called ‘deliberative turn’ (Dryzek 2002), one dimension of the political process moved to be the focus of attention: the quality of deliberation (see Steiner et al. 2005). Deliberation is defined in different ways6 and means basically the rational, wide-ranging exchange of arguments leading to optimal solutions (see Rucht in this volume). Deliberation is also crucial in theories on representative democracy, where it is located mainly in representative, elected bodies. In contrast, proponents of deliberative democracy focus primarily on deliberation among citizens. They argue that citizens’ preferences are poorly grounded without deliberation; thus elections just lead to the aggregation of citizens’ ‘crude’ preferences and do not necessarily result in optimal solutions. As Levine et al. (2005: 274) put it: ‘there is a world of difference between a vote that follows rich deliberation and one on which people simply register their “raw” opinion’. From this point of view, it is necessary to improve the unsophisticated aggregation democracy (see Fishkin in this volume). Some authors even argue that it would be dangerous to give citizens more options to make political decisions (e.g. in direct democratic procedures) without providing them with sufficient opportunities for public deliberation. So, the quality of deliberation is an important criterion for the evaluation of participatory innovations. However, the measurement of deliberation is controversial. European authors often refer to Habermas’ concept of deliberation, which includes strict rules, for example the rational exchange of arguments among free and equal citizens. In contrast, US proponents apply less high standards and regard most kinds of discussion as deliberation. Recently, some indices to measure the quality of democracy have been worked out (see Fishkin and Rucht in this volume; Steiner et al. 2005; Bachtiger 2005).