Jean-Paul Sartre's existentialism proposes that the self is created and re-created in every moment of life through choice manifested in action. The Flies explores this idea through dramatic fiction. The ancient myth of Orestes and Electra becomes a story about choosing and creating identities. The story's protagonist becomes its existential hero when he recognizes that he has personal freedom, and chooses a value system of his own. The negative examples are those who refuse to choose at all, or those who choose and then regret their decisions on account of someone else's judgment.
For Sartre, not choosing a value system at all (represented by the action of the Tutor) is worse than choosing a problematic one (represented by Aegisthus).