The existentialist limitation of reality to existence is the core of ancient Greek materialism and is expressed in philosophy by the Atomists as well as in tragedy, in which the terrifying realization that there is nothing beyond existence is given dramatic form. In the Middle Ages, the philosophy of Johannes Scotus Erigena posits existence and nothingness, along with the nonexistence, which is to say the supraexistence, of God. Like the modern religious existentialist, Erigena begins with existence and therefrom commits himself to his conceptualization of deity.
Modern existentialism begins with, and receives its name from, Kierkegaard’s religious writings and his subjective view of existence. Atheistic existentialism follows in the literary work of Friedrich Nietzsche. Kierkegaard’s concept of Angst (as discussed in his Begrebet Angest, 1844; The Concept of Dread, 1944) holds that fear without object—that is, the sense of fear unaccompanied by a knowledge of what one is afraid of—is one’s fear of nothingness and the beginning of one’s need for something beyond existence, which can be experienced only in religious faith. Nietzsche expressed the inability of modern people to believe in the god of primitive and medieval Judaeo-Christianity as the death of God and called upon humankind to transform itself into a higher kind of being.
In the twentieth century, existentialism developed in the philosophical school of Sartre, Simone de Beauvoir, and Maurice Merleau-Ponty. This school combined a Kierkegaardian view of existence and a Nietzschean irreligiousness with phenomenology (a subjective inquiry into the nature of the forms of consciousness). Religious thinkers who adhered to the confrontation with existence as antecedent to the determination of essence included Martin Buber and Gabriel Marcel.