Although Aeschylus is considered to be the first great innovator of Western drama, it is sometimes difficult to judge the full extent of the innovations he introduced, since no plays by his predecessor, Thespis, have been preserved. What we know about Greek drama before Aeschylus suggests that it had developed gradually out of choral lyrics, occasionally interrupted by short dialogues between the chorus and a single speaker or singer representing an individual character. Aeschylus took the decisive step of introducing a second actor, thus enabling for the first time a dialogue or conflict between two individuals to take place on the stage and in front of an audience. The innovations made possible by Aeschylus’s introduction of a second character are very significant. In addition, an actor could leave the stage and reappear in the guise of another character, thus permitting an increase in the overall number of persons represented. In his later plays, Aeschylus used three actors, allowing him to feature a large number of characters, as in The Libation Bearers, the second play of the Oresteia trilogy.