The crux of Existentialism is Human Freedom, the freedom of the living human individual. The movement that was both literary and philosophical saw an individual as the basic entity of society who was in command of the world around him and acted freely and responsibly to find his place in society.
For an existentialist, individual and not organized society or religion was the centre of the whole existence. For him, the authenticity in life meant living individually, an existence that didn’t owe to society or religion.
Existentialism worked on the concept of ‘me Vs them’ or ‘individual Vs the society’ and firmly believed in an individual’s supremacy rejecting the established philosophical notions as too abstract and detached and thus showed disorientation and tension an individual had with existing norms revolving around with themes like life and death, freedom, existence and bondage, anxiety and authenticity, angst and despair and so on.
Basically called a 20th Century philosophy and used by French philosopher and legend Jean-Paul Sartre to describe himself, though he once famously said “Existentialism? I don’t know what that is”, it had its roots in the works of 19th Century philosophers Friedrich Nietzsche and Søren Kierkegaard.
Existentialism gave rise to a cultural movement in 1940s and 50s Europe in the post World War II period and Martin Buber, Karl Jaspers, Martin Heidegger, Jean Wahl, Gabriel Marce, José Ortega y Gasset, Miguel de Unamuno, Nikolai Berdyaev and Lev Shestov were the major Existentialists the movement produced.