When it’s a matter of qualifying the participatory or deliberative democracy devices and their participants, some continue to oppose their institutional designs according to whether lay people or concerned citizens - with regard to the issue put under discussion - are taking part. The project of institutionalized resorting to the Consensus Conferences - renamed Convention de citoyens by Jacquemot - promoted by some French key academics in deliberative democracy, actualizes this opposition. This paper proposes to go beyond it by considering the citizenship in practice. It shows that the question: "which public participates?" cannot be assessed according only to substantial selection criteria, but rather according to what the participants actually do during the discussion. For this purpose, the article compares the discursive activity and the conducting of the debat characterizing two related deliberative arrangements: an open public debate and a consensus conference organized within it. As a conclusion, the paper shows that the discursive activity expended in the two devices is not so much that of lay persons or concerned citizens but more that of a public of "amateurs", as Bruno Latour (1993) depicted himself as an amateur of sciences: amateurs literally taste, enjoy and assess the strengths and weaknesses of public policies.
Keywords: Participatory Democracy, Deliberative Democracy, Public Debate, Consensus Conference, Citizenship