Existentialism is a chiefly philosophical and literary movement that became popular after 1930 and that provides a distinctive interpretation of human existence. The question of the meaning of human existence is of supreme importance to existentialism, which advocates that people should create value for themselves through action and living each moment to its fullest.

Existentialism serves as a protest against academic philosophy and possesses an antiestablishment sensibility. It contrasts both the rationalist tradition, which defines humanity in terms of rational capacity, and positivism, which describes humanity in terms of observable behavior.

Existential philosophy teaches that human beings exist in an indifferent, objective, ambiguous, and absurd context in which individual meaning is created through action and interpretation.

Although there is a diversity of thought in the movement, its thinkers agree that all individuals possess the freedom and responsibility to make the most of life. Existentialists maintain the principle that "existence precedes essence," an observation made by Jean-Paul Sartre (1905–80), atheist humanist and the only selfproclaimed "existentialist." This principle advocates that there is no predefined essence of the human being and that essence is what a human makes for itself.

Each of the existentialist thinkers, however, worked out their own interpretations of existence. Søren Kierkegaard (1813–55), a religious Danish philosopher known as the "father of existentialism," possessed a belief in the Christian God. He attacked abstract Hegelian metaphysics and the worldly complacency of the Danish Church.

Kierkegaard believed that individual existence indicates being withdrawn from the world, which causes individual self-awareness. Individuals despair when confronted with the truth that their finite existence emerged detached from God.

This despair, thus, gives rise to faith, despite the absurdity of that faith. Other philosophical precursors who are believed to have influenced modern existentialist philosophy include St. Thomas Aquinas (1224–74), Blaise Pascal (1623–62), Fyodor Dostoyevsky (1821–81), and Friedrich Nietzsche (1844–1900).

German philosopher Martin Heideger (1889–1976) believed that the starting place for philosophy should be studying the nature of the existence of the human being. In his book Being and Time (1962), he intended to provoke people to ask questions about the nature of human existence. He intended that such questioning would have the result of causing people to live a desirable life and "possess an authentic way of being."

Several French authors possessed existentialist beliefs. Parisian-born Gabriel Marcel (1889–1973) advocated that the purpose of philosophy was to elevate human thinking to the point of being able to accept divine revelation.

He coined the term existentialism in order to characterize the thought of Sartre and his lifelong friend and associate Simone de Beauvoir (1908–86). De Beauvoir, a Parisian existentialist author and feminist, penned She Came to Stay (1943) and The Blood of Others (1945).

These works suggested that the viewpoint of someone else is necessary for an individual to have a self or be a subject. Jean-Paul Sartre, also a Paris native, popularized existentialism in his widely known 1946 lecture "Existentialism and Humanism." The lecture set out the main tenets of the movement.

Taking Sartre's lead, existentialists rejected the pursuit of happiness, as it was believed to be nothing but a fantasy of the middle class. Sartre's existential thought can best be observed in his novels Nausea (1938), credited as the manifesto of existentialism, and No Exit (1943).

Existential thought became further disseminated through Sartre's colleagues, who included Maurice Merleau-Ponty (1908–61) and Albert Camus (1913– 60). Merleau-Ponty sought to provide a new understanding of sensory phenomena and a redefinition of the relationship between subject and object and between the self and the world.

Perhaps the most influential and well-known 20th-century existential writers, Sartre and Camus, also took part in the French Resistance, having been galvanized by the atrocities of World War II. Although the only self-professed existentialist was Sartre, the other thinkers associated with the movement are associated with it because of their similar beliefs.

Camus wrote novels concerned with the existential problem of finding meaning in an otherwise meaningless world and taking responsibility for creating human meaning. He advocated that the chief virtue of humanity was the ability to rebel against the corrupt and philosophically undesirable status quo.

From the 1940s on, the movement influenced a diversity of other disciplines, including theology, and thinkers such as Rudolf Bultmann (1884–1976), Paul Tillich (1886–1965), and Karl Barth (1886–1968), whose 1933 biblical commentary on the Epistle to the Romans inspired the "Kierkegaard revival" in theology.

The principles of existentialism entered psychology through the 1965 work of Karl Jaspers (1883–1969), General Psychopathology, and influenced other psychologists such as Ludwig Binswanger (1881–1966), Otto Rank (1884–1939), R. D. Laing (1927–89), and Viktor Frankl (1905–97).

Other writers who expressed existentialist themes included the marquis de Sade (1740–1814), Henrik Ibsen (1828–1906), Hermann Hesse (1877–1962), Franz Kafka (1883–1924), Samuel Beckett (1906–89), Ralph Ellison (1914–94), Marguerite Duras (1914–96), and Jack Kerouac (1922–69). The work of artists Alberto Giacometti (1901–66), Jackson Pollock (1912–56), Arshile Gorky (1904–48), and Willem de Kooning (1904–97) and filmmakers Jean-Luc Godard (b. 1930) and Ingmar Bergman (1918–2007) also became understood in existential terms.