Sophocles, the most successful of the ancient Greek playwrights, garnered between eighteen and twenty-four victories in yearly competitions at the Festival of Dionysus. He wrote about 123 tragedies, of which seven are preserved. Three concern the family of Oedipus; one relates the story of Deianira and her husband, Heracles; and three are devoted to the Trojan War and its consequences. Electra, Sophocles’ only surviving play about the family of Agamemnon, preserves the basic story as Aeschylus revised it from Homer’s Odyssey (c. 725 b.c.e.; English translation, 1614) but alters the details yet again. The changes help the reader to understand Sophocles’ interpretation of the myth and the yield for humanity that he saw in it.

Homer carefully avoids the horror of matricide in his account of Orestes’ vengeance, recalling that Orestes murdered Aegisthus and properly buried both him and Clytemnestra. Though a number of alternative explanations for Clytemnestra’s death can be advanced, Aeschylus sees matricide implicit in the situation, and in the last two plays of the Oresteia (458 b.c.e.; English translation, 1777), his trilogy about the family of Agamemnon, Orestes is plagued by Furies, or in the vernacular of later ages, “driven mad by guilt” for slaying his mother. He is acquitted when the goddess Athena’s utterly unjustified vote of not guilty breaks the deadlock of an evenly divided jury. Aeschylus is concerned with exploring matters of state: how personal anguish relates to one’s obligations to a slain king and father; how humanity progresses; and what is involved in moving from one system of justice to another, here from blood vengeance to trial by jury.

Sophocles is more interested in the ways in which experience, working with innate qualities, determines a human being’s character. The gods hardly figure in his play, and guilt is not the issue. Given their innate proclivities and experiences, his characters do what they think or feel they must do; the worst of them, Clytemnestra, sees and regrets in some measure the horrors she perpetrated, and the best, Electra, is goaded into encouraging and supporting horrors of equal magnitude.

Noble and idealistic Electra, obsessed by the loss of the father she loved and feeling repugnance for her mother that is tainted with jealousy, abandons all hope of marrying, loving a husband, and bearing children. Instead, she commits herself to the past, to avenging her father’s murder. She hates the usurper Aegisthus and her mother because they mistreat her, and, to a degree, that hatred compromises her desire for moral vengeance. She not only wants revenge but also wants to cause her enemies pain. Her great fear is that she may possess traits inherited from her mother, and the fear is justified. Clytemnestra, if her account of her motive for killing Agamemnon carries any weight, is, like Electra, fiercely committed to justice by blood vengeance. Her hatred and lust, too, are implacable. She waits ten years for revenge, and, gaining it, mutilates the corpse of her victim, husband though he was. She celebrates the anniversaries of his death with festivals. Electra’s transcendent hatred and the lust for vengeance that she nurtures for years mirror Clytemnestra’s; Electra, too, is determined to dishonor the corpse of a culprit, intending to toss the slain Aegisthus as carrion to birds and dogs. Warped by her experiences, the expression of her noble intent is unavoidably impious.

Chrysothemis, Clytemnestra’s middle child, who is less proud and determined than her sister, accepts the condition of servitude in the household of her father’s murderers. She subordinates her unhappiness and hopes for a better life in the future. Unwilling to risk her...