In philosophy the self is the relationship of an individual's own being knowledge and values. Self relates the experiences of one's inner and outer living in presence. The first-person perspective distinguishes selfhood from personal identity. Whereas "identity" is (literally) sameness and may involve categorization and labelingselfhood implies a first-person perspective and suggests potential uniqueness. Conversely "person" is used as a third-person reference. Personal identity can be impaired in late-stage Alzheimer's disease and in other neurodegenerative diseases. Finally the self is distinguishable from "others". Including the distinction between sameness and otherness the self versus other is a research topic in contemporary philosophy and contemporary phenomenology (see also psychological phenomenology) psychology psychiatry neurology and neuroscience.