Born in 1905, Jean-Paul Sartre studied and taught philosophy throughout most of his life. In 1938 he gained fame with the publication of his first novel, Nausea, which attempted to present his philosophical views at the time. The hero of Nausea is an antisocial recluse who, having realized the separation of human consciousness from nature, mocks all political commitment and has particular disdain for people who commit themselves to actions. These views were quickly changed when, in 1940, France was invaded by the German army and placed under the collaborationist Vichy Government of Marshal Petain. The importance of freedom and of political action appeared in Sartre's writings in response to the occupation.

While in a German prison camp in 1940, Sartre wrote and produced a play called Bariona, or the Sun of Thunder, which presented Sartre's newfound belief in the importance of free action. In 1943 he continued in the same spirit, writing The Flies for a performance by some of his friends. The play is a modern adaptation of Aeschylus's The Libation Bearers, and Sartre makes a number of important philosophical points by changing the details of the original text.

Having left the prison camp, Sartre actively involved himself in the French opposition movement called the Resistance. He could not publish anything that attacked Nazi rule directly, since the censors would not allow it. Like several other authors of the same time, Sartre chose a Greek play to provide a cover for his anti-fascist beliefs. The censors missed the message of the play, but the audiences picked it up; it is clear enough in the writing. The conditions in Argos as Sartre describes them closely mirror the state of affairs in France. Aegistheus murders the true king of Argos and takes his place, while the queen, Clytemnestra, gladly joins him and supports his every repressive action. Aegistheus clearly stands for the German occupation, while Clytemnestra represents the collaborationist Vichy government. The Flies is a call to the French people to recognize their freedom to act and rise up against their oppressors.

Resistance politics was not the only driving force behind the play, which is why it still holds an interest for us today. In 1943, the same year The Flies was written and performed, Sartre published his major philosophical work, Being and Nothingness. In this book, freedom takes center stage. Human consciousness is not bound by natural laws: it can interpret them and decide how to act on them. Sartre explains, in page after page of meticulous detail, the various ways in which human beings may become blinded to their freedom. The picture of humanity that results from that is somewhat drastic: human beings are completely alone in the world, isolated from each other and their environment, but absolutely free to choose their actions, create their meaning, and interpret the world.

By this point Sartre had clearly moved beyond the themes in Nausea. Human alienation from the surrounding world is no longer his dominant obsession. Far more important is what this alienation gives rise to: freedom. This development in his philosophy gave Sartre a way to combine his philosophical beliefs with his political ones, since both aspire towards the same ideal. The Flies is a major attempt to combine philosophy and politics in order to reconcile existentialism and liberalism.