The aim of this introduction is to question, from a methodological and epistemological point of view, the relevance of a comparison of deliberative practices across time and space. Starting from a discussion of different approaches of comparative history, we defend the virtues of a disturbing comparativism—that of “comparing the incomparable? (Detienne)—a “controlled anachronism? (Loraux) shedding new light on past experiences coming from contemporary questions, and also taking into account their historicity to better understand the present dynamics. We then analyze some of the contributions of this issue to the understanding of citizen participation in negotiations, public debates, expertise, and decision processes. The analysis turns around four general questions: the reasons for participation, its actors, its forms, and its effects.