How do stakeholders use their judgment, forge their opinions in public debates concerning socio-ecological issues? What kind of possibilities, but also what pitfalls may arise when resorting to outside expertise? Is there sufficient space provided for the confrontation of values, given that they will necessarily guide collective projects? Analyzing the public debate surrounding the reconstruction of Montreal’s Turcot interchange, but also theoretical and philosophical contributions – among others Hannah Arendt’s concepts of responsibility and judgment – we discuss ethical and political issues raised by those questions. In a creative perspective, and looking towards the development of a learning society, we suggest that expertise should be mobilized in a broader, shared, critical and reflexive exercise.