Because existentialism is treated as a “lived” philosophy that is understood and explored through how one lives one’s life rather than a “system” that must be studied from books, it is not unexpected that much existentialist thought can be found in literary form (novels, plays) and not just in the traditional philosophical treatises. Indeed, some of the most important examples of existentialist writing are literary rather than purely philosophical.
Some of the most significant examples of literary existentialism can be found in the works of Fyodor Dostoyevsky, a 19th-century Russian novelist who wasn’t even technically an existentialist because he wrote so long before anything like a self-aware existentialism existed. Dostoyevsky was, however, very much a part of the 19th century protests against the common philosophical argument that the universe should be treated as a total, rational, comprehensible system of matter and ideas — exactly the attitude that existentialist philosophers have generally criticized.
According to Dostoyevsky and those like him, the universe is much more random and irrational than we want to believe. There is no rational pattern, there is no overarching theme, and there is no way to fit everything in neat little categories. We might think that we experience order, but in reality the universe is quite unpredictable. As a consequence, attempts to construct a rational humanism that orders our values and commitments is simply a waste of time because the rationalized generalizations we create will only let us down if we rely on them too much.
The idea that there are no rational patterns in life that we can rely upon is a prominent theme in Dostoyevsky’s Notes from the Underground (1864), where an alienated antihero struggles against optimistic assumptions of the rationalist humanism around him. Ultimately, Dostoyevsky seems to argue, we can only find our way by turning to Christian love — something that must be lived, not understood philosophically.
Another author commonly associated with existentialism even though he himself never adopted the label would be the Austrian Jewish writer Franz Kafka. His books and stories frequently deal with an isolated individual coping with malevolent bureaucracies — systems that appeared to act rationally, but which upon closer inspection were revealed to be quite irrational and unpredictable. Other prominent themes of Kafka, like anxiety and and guilt, play important roles in the writings of many existentialists.
Two of the most important literary existentialists were French: Jean Paul Sartre and Albert Camus. Unlike so many other philosophers, Sartre didn’t simply write technical works for the consumption of trained philosophers. He was unusual in that he wrote philosophy both for philosophers and for lay people: works aimed at the former were typically heavy and complex philosophical books while works aimed at the latter were plays or novels.
A principle theme in the novels of Albert Camus, a French-Algerian journalist, is the idea that human life is, objectively speaking, meaningless. This results in absurdity which can only be overcome by a commitment to moral integrity and social solidarity. According to Camus the absurd is produced via conflict — a conflict between our expectation of a rational, just universe and the actual universe that it is quite indifferent to all of our expectations.