The Flies is an existential work of fiction that explores Jean-Paul Sartre's philosophical ideas. Sartre's existentialism maintains that existence precedes essence. Man, Sartre says, is nothing inherently. Rather, man continually defines and creates the self through action and choice. Because man has neither pre-existing essence nor pre-determined ideals, man is radically free, and radically responsible for his choices. The result of this freedom is solitude, anguish, fear, and a deep sense of liberation. For Sartre, the proper response is to embrace this freedom, and everything that comes with it, rather than run from it.
The Flies demonstrates that Sartre's existentialism is incompatible with any political ideology.