In his discussion of Ghosts, Fergusson detects elements of three conflicting types of drama in the work: a formulaic "well-made" thriller, a realist "thesis play" about a specific social question, and a traditional tragedy.

The Plot of Ghosts: Thesis, Thriller, and Tragedy

Ghosts is not Ibsen's best play, but it serves my purpose, which is to study the foundations of modern realism, just because of its imperfections. Its power, and the poetry of some of its effects, are evident; yet a contemporary audience may be bored with its old-fashioned iconoclasm and offended by the clatter of its too-obviously well-made plot. On the surface it is a drame a these [thesis play], of the kind [Eugene] Brieux was to develop to its logical conclusion twenty years later: it proves the hollow-ness of the conventional bourgeois marriage. At the same time it is a thriller with all the tricks...