 Disabilities like these have been objects of study in sociology, medicine, and policy debates for much longer than they have been subjects of sustained interest in philosophy. These discourses do not tend to define “disability” by way of the sort of rigorous necessary and sufficient conditions philosophers often prefer. But they have been centrally concerned with broadly definitional issues, often discussed under the heading of “models” of disability—that is, general theoretical perspectives concerned to say what in the world social scientists are investigating when they investigate disability. These models generally pick out, both (1) a set of phenomenon as what needs explaining, when we explain disability, phenomenon typically but not necessarily characterized as disadvantages; and (2) an explanation of these phenomenon—again, typically, but not solely, an explanation of why disabled people experience the disadvantages they do.