The Agamemnon, Choephori, and Eumenides were the last tragedies composed by Aeschylus along with the satiric drama Proteus. The tetra-logy as a whole was called the Oresteia, a name which, appears to have been in use at any rate as early as the time of Aristophanes. The contents of the Proteus are unknown, and its connection with the preceding tragedies obscure; but it probably dealt with the fortunes of Menelaus, the brother of Agamemnon, and related the story of his detention on the coast of Egypt, and his rescue by the help of Proteus, the sea-god.
The subject of the trilogy is one of those dark stories of hereditary guilt, of which the Septem. Atreus had sown the first seeds of woe by his murder of the children of Thyestes; and Agamemnon, later on, had sacrificed the life of his daughter, Iphigenia to his own ambition. The results are unfolded in the Oresteia. Clytemnestra, assisted by her paramour Aegisthus, murders Agamemnon, partly to conceal her adultery, partly in revenge for the loss of her daughter. The murderers are slain in turn by Orestes, who thus incurs the guilt of matricide. For this offense he is exposed to the vengeance of the Furies, who typify the workings of remorse, and by whom he is hunted from place to place, until at length he reaches Athens, where he finds release from his sufferings.
The depth of moral significance which it acquires in the hands of Aeschylus was essentially his own creation. Under his treatment it becomes one of the most solemn and impressive pictures of guilt and retribution which was ever painted by any poet. One thought inspires the whole trilogy from first to last -- the thought of the crimes which have been committed in the past and of the blood which has been shed and which still cries out unceasingly for vengeance. This recollection seems to haunt the very souls of the actors in the successive tragedies. It hangs like a dark cloud over the minds of the Theban elders, damps their joy at the news of the victory, and fills them with gloomy forebodings. It forms the constant burden of those odes in the Choephori, where the chorus justifies the approaching act of retribution. It is never absent from the lips of the Furies, as they pursue Orestes with righteous chastisement.
The introduction of Cassandra, which gives occasion to the finest scene in the play, answers a double object. As an example of the insolence of Agamemnon, in bringing home his captive mistress before the very eyes of his wife, it lessens out sympathy with his misfortune, and fixes our attention on his guilt, in accordance with the moral purpose of the trilogy. At the same time the inspired utterances of the prophetess serve to recall to the minds of the audience those dark crimes of Atreus which were the primal source of the present evil. Another noticeable feature in the Agamemnon is the humorous scene which follows the murder. The sententious ineptitude of the old men, in the presence of the crisis, is one of those passages of semi-comedy with which Aeschylus occasionally relieves the tension of the feelings; and it may be compared with the speeches of the porter which precede the discovery of the murder in Macbeth, or with the bantering dialogue of the gentlemen after the death-scene in the Maid's Tragedy.
Throughout this play the interest is transferred from persons to principles. The human element becomes of less importance, and Orestes and his fortunes sink into the background. Their place is taken by the great gods of Olympus and of Tartarus, who represent opposing ordinances. Law and Justice, typified by the Furies, demand the punishment of the matricide; while Equity, personified by Apollo and Zeus, pleads for the release of the avenger of crime. It is between these mighty combatants that the battle is waged. Guilt is set against guilt, duty against duty, and no decision seems possible. At length Mercy, under the person of Athene, decides in favor of Orestes.