Delight defines Mark Morris' "Dido and Aeneas." Delight in sex, in music, in pathos, in mischief and even evil. Delight despite the ancient tragic story of love betrayed, and despite the historic and political trappings the story has accumulated over the centuries. Running for the second time in Chicago, through Wednesday at the Harris, Morris' hourlong "Dido and Aeneas" carries some major baggage. Choreographed in 1989 for Brussels' Theatre Royal de la Monnaie, it's based in Virgil's "Aeneid," which emphasizes fate, the gods, the destined history of Rome. Henry Purcell's 1689 opera, set to Nahum Tate's libretto, provides not only the music and a political message about England's ascendancy but a different tack on the characters: Dido becomes stronger than Aeneas, and witches, not gods, direct the action.