The characters in Ghosts are trapped. Social obligations, class restrictions, religion, and family have them all in a vice grip. The main character, Mrs. Alving, is trapped by her own hang-ups. Like a good Victorian housewife, she believes she should keep quiet about her unconventional ideas, protect her bad husband's good reputation, and above all be a good mother. Mrs. Alving's syphilitic son wipes out these "shoulds" with his belief in the idea of livsglede, choosing your own personal path to joy. Don't worry about being a good mom, he says. In fact, stop being a mom entirely. In the end, he asks her to put him out of his misery.
By introducing Mrs. Alving to an alternative to duty, Oswald enables her to kills him and free herself at the end of the play.
The characters with the least social standing have the most independence in Ghosts.