The "Journées de l'Economie" are a vantage point for studying the constraints that govern the actions of the expert when facing people other than those he is used to working with. Held in Lyon for the past three years, this event offers three days of conferences officially open to all on a set of themes: crisis, growth, sustainable development, etc. From the survey we conducted during this event, we identify some of the conditions that allow for the in situ development of a critical stance by the audience toward the expert, sometimes even leading to attempts to question his position. These conditions are: the possibility for the people in the room to acknowledge a shared condition; the existence of summation methods for aggregating complaints; and the need for the expert to identify him-/herself as being devoid of self-interest and lacking means to intervene in the field in which he operates. Even if it does not entail systematic public support, this event far from leads to a continual questioning of the experts. Indeed, we show that the event is based on two central presuppositions: on the one hand, the citizens' ignorance about economic issues, and on the other, the existence of a scientific authority likely to remedy this. We therefore argue that one of the dimensions that this event assumes is to confirm the economy as an entity substantial enough that no doubt can remain about its existence.