 One way of conceptualizing the structure of a science is that at any time it contains ontologies, theories, and values (Kuhn 1962; Lakatos 1976; Laudan 1978, 1986). In this entry, we explore questions regarding the ontology, theoretical structure, and values central to conservation biology. First, conservation biology as a discipline has expended a great deal of intellectual effort in articulating exactly what is its object of study and has settled on biodiversity as the answer. However, there is a debate concerning what biodiversity is, and whether it should be center stage in the discipline. Second, conservation biology, though a scientific discipline with its theories, models, experiments, and fieldwork, also utilizes a variety of tools that do not fit into the above categories. That is, some of its core tools are not theories or models in the ordinary sense. Thus, as a discipline, it is appears interestingly unique and ultimately unlike ones that philosophers of science have typically examined. Third, conservation biology was originally articulated by the early pioneers as a “crisis discipline” where certain types of normative concerns were at the forefront. In fact, many have likened it to medicine insofar as it has ethical foundations. In the medical case, it would be the well-being of patients and in conservation biology it is the conservation of biodiversity. Thus, we should ask are the discipline’s aims or values explicitly ethical or sociopolitical and to what extent are they controversial?