The development paths followed by industrial societies in the last decades have led them in front of complex socioeconomic, democratic and environmental crises, which question the relevance of economic growth, either as a goal in itself, or as a way to achieve “development”. With the emergence of the degrowth movement at the beginning of the 21st century, the call for transitions towards sustainable “post-growth societies” is now consolidating into a multifaceted political project. For the “wealthiest” countries, where the ecological footprint per capita is greater than the global sustainable level, this project may be envisioned as a voluntary, socially sustainable, equitable and smooth downscaling of production and consumption, and thus throughput, to an environmentally sustainable level. Such a project raises numerous questions, for instance: what concrete proposals could initiate such a transition? What could such paths induce in terms of employment, public debt, energy consumption, waste, or greenhouse gas emission mitigation? What structural or institutional obstacles must be overcome and how? Etc. In this research, we offer to discuss such questions with the help of prospective modeling. Our approach involves a series of interviews, conducted, among others, with actors within the Degrowth movement. These are aimed at collecting detailed and quantified visions or narratives about what Degrowth scenarios or – more broadly speaking– scenarios of transition towards sustainable and desirable societies could look like, for France, in the mind of participants, especially in terms of institutions, lifestyles and consumption patterns. In parallel, we have designed and developed a specific dynamic simulation model of the French monetary economy, featuring a high level of detail and disaggregation, based on input-output analysis, and built using public data. Using this macroeconomic tool, we investigate, over the long term (2060), the possible outcomes of different scenarios, including those inferred from the interviews, in terms of employment, public debt, energy consumption, waste and atmospheric emissions. We discuss the potential strengths and weaknesses of the different visions they reflect. Our results highlight in particular the importance of cultural, social, behavioral and “non-technical” factors, stress the potential of various degrowth proposals, and recall the critical need for the collective elaboration of a societal project. In this perspective, our modeling approach provides a simple, yet powerful tool for common understanding and collective deliberation.