Ibsen's poetic ability enables him to enrich the prose plays with symbols that have broad as well as narrow meanings. Especially allusive is Ibsen's concept of light and darkness. Oswald's last plea for the sun, for instance, sums up his need for the "joy of life" in himself as well as in his work. He needs sunlight in which to paint and he needs illumination on the nature of his father. A pall hangs over the entire landscape of the play; if there is no rain at the moment, the scene outside the window is obscured by mist. The weather finally clears when Mrs. Alving faces the truth, but it is too late. Thrust into darkness, Oswald weakly cries out for the sun. His last monosyllabic plea has a twofold significance: not only symbolizing the "light of truth," it might stand for the morphia powders which would dispel the lingering darkness that enshrouds Oswald's diseased mind.
The fire that destroys the orphanage is another symbol of truth. Purifying the institution of deceit, the flames allow Engstrand to receive support for his planned Alving Home. With characteristic irony, Ibsen implies that there is no deceit in raising a brothel to the memory of the late Captain Alving.
The most pervasive symbol, of course, is that of ghosts. The ghosts are worn ideals and principles of law and order so misapplied that they have no actual significance. All the untested maxims and abstract dogma that Manders maintains are ghosts; all the sources of personal cowardice in Mrs. Alving are ghosts. Ghosts are also the lies about the past, perpetrated to the present, which will haunt the future. Finally, ghosts are the actual and symbolic diseases of heredity which destroy the joy of life in the younger, freer generations.