The chapter considers the roles played by economics and economists in post-war France both in shaping economic thinking and in influencing policy. It overviews both macro- and microeconomic aspects of the economists’ interventions and argues that the intellectual ethos prevailing in France prompted economists not just to study the markets, but to construct them. It demonstrates, in particular, that with economists being important players within French bureaucratic structures, the normative questions of the ‘goodness’ of markets could be reformulated. In a society characterized by a general mistrust towards markets, the market logic was instrumentalized, and economic thinking was used to apply ‘markets’ primarily to improve the policy/planning process in view of normative visions of optimality suggested and developed by economists.