In sociology and critical social theory, alienation refers to an individual's estrangement from traditional community and others in general. It is considered by many that the atomism of modern society means that individuals have shallower relations with other people than they would normally. This, it is argued, leads to difficulties in understanding and adapting to each other's uniqueness (see normlessness). It is also sometimes referred to as commodification, emphasizing the compatibility of capitalism with alienation (a common theme of the early work of Karl Marx; see Marx's theory of alienation).
Marx's Theory of Alienation is based upon his observation that in emerging industrial production under capitalism, workers inevitably lose control of their lives and selves, in not having any control of their work. Workers never become autonomous, self-realized human beings in any significant sense, except the way the bourgeois want the worker to be realized. Alienation in capitalist societies occurs because in work each contributes to the common wealth, but can only express this fundamentally social aspect of individuality through a production system that is not publicly social, but privately owned, for which each individual functions as an instrument, not as a social being.
There is a commonly noted problem of translation in grappling with ideas of alienation derived from German-language philosophical texts: the word alienation, and similar words such as estrangement, are often used to translate two quite distinct German words, Entfremdung and Entäußerung, interchangeably.
In a broader philosophical context, especially in existentialism and phenomenology, alienation describes the inadequacy of human being or mind in relation to the world. The human mind, as the subject of perception, relates to the world as an object of its perception, and so is distanced from the world rather than living within it. This line of thought can be found in Søren Kierkegaard, who examined the emotions and feelings of individuals when faced with life choices. Many 20th-century philosophers, both theistic and atheistic, and theologians drew many concepts from Kierkegaard, including the notions of angst, despair, and the importance of the individual. Martin Heidegger's concepts of anxiety (Angst) and mortality drew on Kierkegaard and are indebted to the way in which the latter lays out the importance of our subjective relation to truth, our existence in the face of death, the temporality of existence, and the importance of passionate affirmation of one's individual being-in-the-world.
Jean-Paul Sartre described the "thing-in-itself" which is infinite and overflowing, and claimed that any attempt to describe or understand the thing-in-itself is "reflective consciousness." Since there is no way for the reflective consciousness to subsume the pre-reflective, Sartre argued that all reflection is fated to a form of anxiety, i.e. the human condition. As well, Sartre argued that when a person tries to gain knowledge of the "Other" (meaning beings or objects that are not the self), their self consciousness has a "masochistic desire" to be limited, which is expressed metaphorically in the famous line of dialogue from the play No Exit, "Hell is other people."