The importance of freedom is the dominant theme of the play. Sartre's philosophy is built around the idea that human beings are capable of interpreting the world for themselves, thereby creating new values. Freedom is this ability to invent new values and to create oneself and one's own world. Since all other values spring from one's free interpretation of the world, freedom is the foundational value in Sartre's system. Finding the people of Argos enslaved by a moral framework that requires perpetual repentance for past sins, Orestes decides that he must create himself and his world by murdering Aegistheus and Clytemnestra in order to establish himself as one of the Argives and also to set the Argives free from these tyrannical rulers. Since human freedom is the greatest value, it supercedes both the skeptical view that all morals are relative and the god-given moral norm to which all human beings must adhere. Orestes makes his decision to act by freeing himself both of the idea of destiny and of Jupiter's attempts to maintain order. For Sartre, freedom involves both a choice and an action based on that choice; the play is structured around this view of freedom. Act II, the only act with two scenes, shows Orestes making his decision in Scene One and acting upon that decision in Scene Two. Orestes's realization of his freedom thus provides an axis around which the action of the play revolves. Since Sartre wrote The Flies during the Nazi occupation of France, he preaches violent and revolutionary action that frees people from a moral system imposed on them from above.
Responsibility can be related either to guilt or to freedom. To take responsibility for an action may mean to feel guilty about it. The Argives are taught that they are responsible for their sins and must spend their lives repenting of those sins. Orestes flips this view of responsibility around, insisting that one incurs guilt only when one refuses responsibility for an action and repents. Guilt occurs when an individual judges his or her action to be wrong according to the moral norm. Since the highest moral values stream directly from human freedom, one cannot incur guilt if one acts freely. The free actions taken by individuals create their values, so that a free action cannot be wrong according to the agent's moral standards. Orestes takes full responsibility for the murder of Aegistheus and Clytemnestra. As a result, he feels that his action was right since he acted in accordance with his free decision. Electra refuses to take responsibility for the murders because she is afraid of how others will judge her. She refuses responsibility for her part in the murder, so that her participation becomes more of an accident than a human action. Electra is tormented by guilt precisely because she refuses to accept her action as her own and attempts to place all the responsibility on Orestes. As a result she feels that it is he who ruined her innocence.
Free action requires an engagement with the future. The Argives are not free because they look only towards their past and the sins they have committed. They are incapable of freely shaping their lives because the burden of their past keeps them from creating new values. Their values are set in stone, and their lives consist of judging the same old sins by the same old moral standards. In order to act freely, one must interpret one's past instead of letting an interpretation be imposed by someone else. Orestes, the only free character in the play, acts in order to create himself; he acts for the sake of his future. Electra, on the other hand, acts out of revenge for the past. She looks ahead to only one event in her future: her bloody vengeance. Once this event has occurred, Electra can only look backwards and cannot recognize her freedom.