The central question for this topic area is the following: what constitutes well-being or welfare for non-human animals? Many of the same questions that have been raised about human well-being (and ill-being) can also be raised in regards to other animals, but with additional challenges posed by uncertainty about sentience in different species, debates about the relevance of various cognitive capacities which may be absent, and difficulties in measuring well-being in the absence of verbal self-report. Many of the important ideas related to this theme were developed in works that are not specifically about animal well-being but rather discuss it as part of a larger project. For example, most animal ethics accounts include some discussion of animal welfare, and many accounts of well-being in humans have implications for welfare in other species. To keep this topic area focused, however, works will be included only if they include some specific and at least somewhat extended discussion of questions about the nature of animal well-being or welfare.