A term applied to a group of attitudes current in philosophical, religious, and artistic thought during and after World War 11, which emphasizes existence rather than essence and sees the inadequacy of the human reason to explain the enigma of the universe as the basic philosophical question. The term is so broadly and loosely used that an exact definition is not possible. In its modern expression it had its beginning in the writings of the nineteenth-century Danish theologian, Soren Kierkegaard. The German philosopher Martin Heidegger is important in its formulation, and the French novelist-philosopher Jean-Paul Sartre has done most to give it its present form and popularity. Existentialism has found art and literature to be unusually effective methods of expression; in the novels of Franz Kafka, Dostoyevski, Camus, and Simone de Beauvoir, and in the plays and novels of Sartre and Samuel Beckett, and the plays of Eugene Ionesco, it has found its most persuasive media.
Basically the existentialist assumes that existence precedes essence, that the significant fact is that we and things in general exist, but that these things have no meaning for us except as we can create meaning through acting upon them. Sartre claims that the fundamental truth of existentialism is in Descartes formula, "I think; therefore, I exist." The existential philosophy is concerned with the personal "commitment" of this unique existing individual in the "human situation." It attempts to codify the irrational aspect of human nature, to objectify nonbeing or nothingness and see it as a universal source of fear, to distrust concepts, and to emphasize experiential concreteness. The existentialist's point of departure is the immediate sense of awareness that human beings have of their situation. A part of this awareness is the sense they have of meaninglessness in the outer world; this meaninglessness produces in them a discomfort, an anxiety, a loneliness in the face of human limitations and a desire to invest experience with meaning by acting upon the world, although efforts to act in a meaningless, "absurd" world lead to anguish, greater loneliness, and despair. Human beings are totally free, but they are also wholly responsible for what they make of themselves. This freedom and responsibility are the sources for their most intense anxiety. Such a philosophical attitude can result in nihilism and hopelessness, as, indeed, it has with many of the literary existentialists.
On the other hand, the existential view can assert the possibility of improvement. Most pessimistic systems find the source of their despair in the fixed imperfection of human nature or of the human context; the existentialist, however, denies all absolute principles and holds that human nature is fixed only in that we have agreed to recognize certain human attributes; it is, therefore, subject to change if human beings can agree on other attributes or even to change by a single person if the person acts authentically in contradiction to the accepted principles. Hence, for the existentialist, the possibilities of altering human nature and society are unlimited, but, at the same time, human beings can hope for aid in making such alterations only from within themselves.
In contradistinction to this essentially atheistic existentialism, there has also developed a sizable body of Christian existential thought, represented by men like Karl Jaspers, Jacques Maritain, Nicolas Berdyaev, Martin Buber, and Paul Tillich.
from A Handbook to Literature by C. Hugh Holman, 4th ed.