 The concepts of mental disorder, or illness, are ascribed to deviations from normal thoughts, reasoning, feelings, attitudes, and actions that are by their subjects, or by others, considered socially or personally dysfunctional and apt for treatment. Schizophrenia, depression, obsessive-compulsive disorder, substance abuse, and mania are examples. The concept of mental disorder or illness plays a role in many domains, including medicine, social sciences such as psychology and anthropology, and the humanities, including literature and philosophy. Philosophical discussions are the primary focus of the present entry, which differs from the entry on Philosophy of Psychiatry in noting several different approaches—not only those of the philosophy of science and mind, but also those arising from phenomenological and social theory traditions.