The importance of Aeschylus in the development of the drama is immense. Before him tragedy had consisted of the chorus and one actor; and by introducing a second actor, expanding the dramatic dialogue thus made possible, and reducing the lyrical parts, he practically created Greek tragedy, as we understand it. Like other writers of his time, he acted in his own plays, and trained the chorus in their dances and songs; and he did much to give impressiveness to the performances by his development of the accessories of scene and costume on the stage.

Of the seventy or eighty plays which he is said to have written, only seven survive: "The Suppliant Maidens," on the daughters of Danas; "The Persians," dealing with the defeat of Xerxes at Salamis; "The Seven against Thebes," part of a tetra logy on the legend of Thebes; "Prometheus Bound," part of a trilogy, of which the first part was probably "Prometheus, the Fire-bringer," and the last, "Prometheus Unbound; " and the "Oresteia (The House of Atreus)," the only example of a complete Greek tragic trilogy which has come down to us, consisting of "Agamemnon, Choephorae (The Libation-Bearers)," and the "Eumenides (The Furies)."

The Oresteian trilogy on "The House of Atreus" is one of the supreme productions of all literature. It deals with the two great themes of the retribution of crime and the inheritance of evil; and here a parallel may be found between the assertions of the justice of God by Aeschylus and by the Hebrew prophet Ezekiel. The nobility of thought and the majesty of style with which these ideas are set forth give this triple drama its place at the head of the literary masterpieces of the antique world.