Ibsen actually subtitled Ghosts "A Family Drama." In the 19th century context, this almost seems like a dark joke. Can you imagine Mr. and Mrs. John Q. Norway settling in for a nice exploration of family values in the theater, only to be met with adultery, STDs, incest, and assisted suicide? Puncturing those middle-class expectations was just what Ibsen has in mind. Instead of serving up idealized family life, Ibsen wanted to tell it like it was.
Which brings us to Realism. Realism was a reaction to Romanticism and sought to portray people and events as they are in life. This doesn't mean that Ibsen is a documentarian, or that he's only interested in psychology. He's interested in the biggest and deepest ideas. The interesting thing about Ibsen – actually the dumbfounding, awe-striking, jaw-dropping thing – is that he was able to stage titanic clashes of worldview using every day people in average living rooms. A lamp isn't just a lamp; it's a precursor to the life-giving sun that Oswald needs. Oswald isn't just an ill son; he bears the torch of the joy of life.
And Mrs. Alving doesn't have to be a queen or a god to be a tragic hero, as is the case in much traditional tragedy. She's just a woman. But her journey of self-knowledge, her battle with society, and her courageous reckoning with her flaws earn her our respect and admiration, and earn Ghosts the status of tragedy.