Melodrama is the popular theatrical form Ibsen used to express his ideas. Ibsen goes far beyond the traditional signposts of melodrama – think stock characters, contrived plots, and suspense. In fact, he is indebted to the form for much of the way he uses language.
There are a lot of speeches in this play. In musical theater (another form indebted to melodrama) they are "I Am" songs. The declare what a character believes him or herself to be: I am an artist, I am a priest, I am changing my mind about some things. We could argue about which of Mrs. Alving's speeches is the most important, but there's no arguing that the "ghosts" speech is in the running:
Ghosts! When I heard Regina and Oswald in there, it was as though ghosts rose up before me. But I almost think we are all of us ghosts, Pastor Manders. It is not only what we have inherited from our father and mother that "walks" in us. It is all sorts of dead ideas, and lifeless old beliefs, and so forth. They have no vitality, but they cling to us all the same, and we cannot shake them off. Whenever I take up a newspaper, I seem to see ghosts gliding between the lines. There must be ghosts all the country over, as thick as the sands of the sea. And then we are, one and all, so pitifully afraid of the light. (2.85)
In Ghosts, if a scene doesn't end with a speech, it needs to end with speed, increasing tension and excitement up to the finish line. That means short, quick lines of dialogue, like at the end of Act 2, when Regina discovers the fire:
REGINA. [Cries out.] The Orphanage is on fire!
MRS. ALVING. [Rushing to the window.] On fire!
MANDERS. On fire! Impossible! I've just come from there.
OSWALD. Where's my hat? Oh, never mind it – Father's Orphanage – ! [He rushes out through the garden door.]
MRS. ALVING. My shawl, Regina! The whole place is in a blaze!
MANDERS. Terrible! Mrs. Alving, it is a judgment upon this abode of lawlessness.
MRS. ALVING. Yes, of course. Come, Regina. [She and REGINA hasten out through the hall.]
MANDERS. [Clasps his hands together.] And we left it uninsured! [He goes out the same way.] (2.413-420)
Once they discover the fire, everyone is running every which way and spouting brief, instinctive reactions. Only Pastor Manders – often the butt of Ibsen's jokes – tries to get in a mini-sermon along the way. Ibsen also gives him the semi-comic insurance line that gives the scene its "button."