What new judgment (krisis) does the ecological crisis bring to economics? That the earth is not a space of available resources, but that it is made up of a web of multiple interactions, which geophysicists call the « critical zone ». This new representation radically challenges the modern conception of the economic agent, which was previously assumed to be distinct from its environment and that nothing was forcing him to act on it. With the ecological crisis, every agent appears to be inserted into an environment, which he modifies in an irreversible way without even having decided to do so. This changes in depth, cosmologically, so to speak, the way in which economics can represent the agent and the optimal action. In other words, it is rationality itself that is modified. We would like to develop here some aspects of this new rationality, which we call « ecological rationality ». By this we mean a rationality that takes the measure of ecological knowledge, that is, of the agent’s « insertion » into an environment. Our aim is not to scientifically deduce a rationality from observed behaviors, but to formulate a just rationality, adapted to new knowledge; it has a normative aim and comes under the heading of “practical” economics, in the Aristotelian sense of a good or virtuous economy.
