Too many concepts have now invaded bookstores and academic conversations: “ecology”, “ecologism”, “humans and non-humans”, “nature” and “naturalism”, “decolonial”, etc. But semantic effects must be dissociated from conceptual questions. Under “the living”, similar issues to those that were highlighted under other names such as “life”, “nature” or simply “ecology”, as shown in particular by the detailed works of Serge Audier (Audier 2017, 2019, 2020) or the Basic Text of Friends of the Earth France (Vrignon 2024). This long introduction aims to clarify what ecology is, as a science; what the future may be (scenarios); what do we understand with the concept of "nature"; how decoloniality and the critique of development have been a part of ecologism since the beginnings; and what kind of science is necessary.