Perhaps best embodied in the characters of Electra and Chrysothemis respectively, the opposing value systems of justice and expedience come into frequent conflict throughout the play. Electra adheres strongly to the principle of justice, willing to suffer and mourn continually in its name and in its pursuit. Chrysothemis, on the other hand, while indeed she recognizes that Electra is morally right in her position nonetheless bends towards expedience; "benefit," for her, is a key word: she performs those actions from which she will derive greatest benefit, regardless of whether or not they are necessarily "just."
The value systems collide also in Electra's debate with Clytemnestra about the nature of Clytemnestra's murder of Agamemnon. According to Electra, the murder was motivated by expedience; Clytemnestra had to remove Agamemnon so that she could be with Aegisthus, the object of her lust. According to Clytemnestra, however, the murder was just; she was exacting revenge from Agamemnon for his sacrifice of their daughter. The characters even deliberate whether the sacrifice itself was motivated by expedience or by justice, as a requirement of the gods. The collision of the ideas of justice and expedience functions again and again throughout the play to call into questions the motivations behind key characters, complicating a clear comprehension of their morality and of traditional conceptions of heroes and villains.
Electra's hatred for her mother and her all-consuming desire for revenge bring about powerful changes in her psyche that point clearly to the profound effect revenge can have on its perpetrator. At the outset of the play, Electra adheres strongly to the principles of justice. As the play progresses, however, and the moment of revenge approaches, Electra grows increasingly irrational, demonstrating a questionable grasp on the very principle of justice by which she claims to be motivated. Her enthusiasm in listening to the cries of her dying mother, her refusal to allow Aegisthus to speak before his death, and her desire to desecrate his body by throwing the corpse to scavengers all suggests the maddening potential of the pursuit of revenge. Indeed, many scholars are divided over whether Electra's victory over her mother represents the triumph of justice or the downfall of Electra.
Again and again throughout the play, characters make reverent reference to the abstract concept of honor and guard wildly against dishonor. In his prayer to the household gods at the start of the play, Orestes begs not to be exiled from honor but rather to succeed in his mission and gain his rightful command over the house. One of Electra's preoccupations, too, is preserving and ensuring the honor of her family, her father, and herself. She claims that she mourns to honor her father, and in a similar vein the chorus relates that she has made her life a "wall of tears against dishonor." Clearly, then, there is a sharp and important division between the states of honor and dishonor. This division is perhaps best explained at Electra's lowest point of degradation, just after Orestes has asked her to return the urn to him. Already, she has been ill treated and abused by her mother, betrayed and abandoned by her sister, and left hopeless and helpless by the news of her brother's death. When the disguised Orestes then tells her that she might not keep her brother's ashes, she asks if she has been so dishonored by the dead, as well. The definition of dishonor, here, comes out of the abstract and into its clearest focus: "dishonor" is degradation, betrayal, and abandonment, and it is this state that the play's characters so strive to avoid.
Entrapment reveals itself in the ways in which the various characters try to affect each other. Orestes is instructed by Apollo to "snare" his father's killers as if in a trap similar to the one in which his killers have caught the palace and its inhabitants. Electra refers to her mother in the Second Episode, for instance, as a "cage locked around her life." Electra feels trapped not only by her mother, but also by her desire for revenge; in her initial exchange with the chorus, she claims that she "sees the trap closing" as her desire for revenge intensifies almost beyond the point of control. Finally, as he recognizes Clytemnestra's corpse, Aegisthus acknowledges that he has been "caught" and that vengeance is upon him.
On many occurrences throughout the play, the idea of "breeding" surfaces in reference to a variety of things. The chorus relates that Clytemnestra and Aegisthus have "bred a thing shaped like a monster" and that with her constant mourning Electra "breeds enemies;" also prevalent is the idea of "breeding violence out of violence." In each of these cases, what is "bred" is not natural, pointing to the disturbance of the natural process and order wrought by Clytemnestra's and Aegisthus's actions; all that the characters can breed, until natural order has been restored with Orestes's return, are such unnatural things as monsters, enemies, and violence.
The concept of freedom ultimately serves both to contrast with the idea of entrapment and to emphasize the psychology of different characters in the play. For Chrysothemis, the epitome of one ruled by expedience, "freedom" is gained by obeying one's masters and hence retaining the benefit of creature comforts those masters can bestow. Clytemnestra's moment of freedom comes with the news of Orestes' death; she is, consequently, free from the fear of revenge and her life's disruption. For Electra, freedom consists of the release from her suffering, realized only with Orestes's return and the exaction of revenge; Orestes has the power both to release her from her "cage" of suffering and dishonor and to steal from Clytemnestra her sense of freedom with his snare-like trap of revenge.
The tree is a symbol, ultimately, of the natural order of Agamemnon's rule, so violently corrupted by his murder and the usurpation of his power. Electra refers to Agamemnon as an "oak" cut down by Clytemnestra and Aegisthus several times throughout the play, and the tree that grows from Agamemnon's scepter in Clytemnestra's dream is a clear omen of the restoration of natural order to be brought about by the return of the legitimate heir, Orestes.
The doorway, or threshold, is symbolic of the division between honor and dishonor, good and evil, light and dark. It is where Electra spends all of her time, half inside, half out on the street, as if waiting to bring goodness (Orestes) inside to purge the evil (Clytemnestra and Aegisthus). Yet as the play progresses and Electra loses her grip on rationality and the morality of the revenge comes into question, the distinction between inside and outside is fittingly blurred. Aegisthus, at the very moment of revenge, demands that the gates and doors be opened wide, in effect erasing the doorway as the lines between moral and immoral fade with the exaction of revenge.
Throughout the play, Electra's intense desire for revenge is symbolized as a knot—one that no one, she claims, can untie, as it grows tighter and stronger with each passing day that she must live amongst evil and corruption. Revenge alone does not suffice, either. Electra demands the desecration of Aegisthus's body and the prohibition of his speech, or the violation of justice, as the only conditions under which the "knot" of evil inside of her can be loosened.