This preface to the methodological part discusses how normative theories of deliberation can be studied empirically. Despite major advances in deliberative methodology, the preface identifies two challenges: on the one hand, quantitative work on deliberative processes still struggles with the challenge of causality, requiring the development and application of more sophisticated quantitative designs; on the other hand, there is an urgent need for better understanding the variegated meaning of deliberative acts, requiring more qualitative approaches. The chapter calls for a “problem-based” approach to studying deliberation empirically, combining advanced quantitative and qualitative designs, and suggests that new methodological tools may need to be developed or borrowed from other disciplines.