 There is, not surprisingly, disagreement about how to define cognitive or intellectual disability. (We will use these terms interchangeably, ignoring, unless specifically relevant, their apparent differences in breadth and emphasis.) There are competing psychometric and functional definitions, based respectively on standard deviations from the mean score on intelligence tests and on “significant limitations both in intellectual functioning and in adaptive behavior, which covers many everyday social and practical skills” (American Association of Intellectual and Developmental Disabilities, 2011). For this entry, we will consider individuals defined as cognitively disabled in functional terms, because our interest is in the moral relevance, if any, of the absence or substantial limitation of critical cognitive functions. These limitations are more likely to be captured by functional than psychometric tests, though as we discuss later, the former as well as the latter may fail to detect significant intellectual capacities. We will not assume that, or examine whether, individuals with psychometrically-defined “severe” or “profound” intellectual disabilities are functionally disabled in this way.