“Newly arrived in this land of Thebes, I am Dionysus, son of Zeus, whom Semele, child of Cadmus, once bore, delivered by the lightning-flame. I have changed my appearance from a god’s to a man’s, as I come to Dirce’s stream and the waters of Ismenus.”

The opening lines of the play belong to Dionysus, who delivers the prologue. His speech announces the setting (Thebes, his mother’s home city), the related myth (his divine parentage and unusual birth), and the mortal disguise he assumes for his visit. Bacchae is the only known Athenian tragedy to feature a god who remains disguised as a mortal for the duration. It is a significant feature, as Dionysus repeatedly mentions that he is disguised. Even the Chorus of Bacchants, who have followed him to Thebes from Asia, does not seem to know that he is really Dionysus.

“The city must learn its lesson however reluctantly, that it lacks the blessing of my rites. I must defend the cause of Semele, my mother, by showing myself to mortals as the god she bore to Zeus.”

When the play opens, Dionysus has already caused his aunts, Cadmus’ daughters, to go mad because they rejected the notion that Zeus fathered their sister Semele’s baby. Here, he suggests that his motivation for punishing Thebes has a personal dimension: defending his mother’s honor. Perhaps his insistence on a mortal disguise reflects the duality of his motivations—not only to ensure that his divinity is respected but also that Semele is respected as the mortal mother of a god.