Haak, Christian.2014-10-2120002000AAINQ57352http://hdl.handle.net/10222/55701This thesis investigates the equilibrium concept in population ecology. Equilibrium is a state in which something is in balance. What is in balance and why? This two-part question has concerned ecologists for decades and is still debated today. One influential account postulates density-dependent mechanisms in the population as leading to equilibrium densities. This account suggests a form of self-regulations of populations. However the existence of density-dependence and even the importance of regulation are hotly contested issues in ecology.Focusing on the debate about equilibrium, I follow a form of naturalized epistemology, in which knowledge is to be understood by looking into the workings of science itself. I examine, in particular, the scientists' reasons to hold on to the concept of equilibrium. I describe these reasons as justifying the use of the concept. To understand the debate about equilibrium we need to answer the question: "How is equilibrium justified?"I show that during the debate the justification of equilibrium has changed due to a change in reference of 'equilibrium'. With 'equilibrium' being defined as the outcome of density-dependent processes, equilibrium has come to be understood as a statistical property of a data set. This change in how the application of the concept is justified is a change that has itself been negotiated by scientists in debating their claims about equilibrium. I investigate this negotiation process and argue that it cannot be explained away by referring to the use of models to understand equilibrium. On the contrary, thinking of theories as models makes the investigation of negotiations even more important.The negotiation of equilibrium is a normal scientific process. What is negotiated is the relation between evidence and theory, and I maintain that this relation has to be understood in historical terms. The justification of the equilibrium concept is based on evidence, but also on interests, and scientific practice. Although this historical perspective does not explain all aspects of how the concept is justified, it offers an understanding of the concept that is critical to evaluating its use in population ecology.Thesis (Ph.D.)--Dalhousie University (Canada), 2000.Biology, Ecology.Philosophy.History of Science.text