Henrik Ibsen uses characterization effectively in A Doll's House to enhance the role of each character and the effect they play on the main character, Nora.
Equally, he uses Nora as a way to bring out the main theme of the play, which is the unfair consequences that happen to people that may have their hearts in the right place, but their actions are still in direct contrast with social expectations.
Nora is characterized as a childish and oblivious young wife and mother whose role is to please and entertain her husband and children. However, when she oversteps the social expectations of servitude placed upon women by acting on behalf of her husband (something as simple as borrowing money to save her husband), she gets immediately chastised As a result of seeing her efforts unappreciated, Nora leaves her family in a state of disillusion, depression, and disorientation. Although she does not know what her next step is going to be, it is obvious to her that anything is better than to be insulted by the one person for whom she gave up her right to be happy.
Mrs. Linde is characterized as Nora's foil. Her character is meant to be the opposite of Nora. She has lived through painful times and has already learned about the cruelties of life. Mrs. Linde serves as a guide to Nora's inner thoughts, and not as a judge of them. She seems to expect very little of Nora, as well. She represents a real, warm-blooded woman. Nora, in contrast, shows us the silliness of her person through her nonsensical behavior towards her husband, and the world.
Helmer is an enabler to Nora. He gives her a false sense of control over him by allowing her to serve as his personal entertainment; as a "doll in a doll's house". He reasserts his role as "the man of the house" by belittling Nora's role as a caretaker. The way he does this is by giving her pet names that reflect his condescension. As the main bread-winner, he may also feel as if he deserves that much from Nora. When he sees that there is more to Nora than just a "lark", or a "squirrel" of his own, his manhood becomes affected and he decidedly rejects to appreciate the sacrifices that she made for him. In the end, he ends up alone and abandoned by a disillusioned Nora.
Like Linde, Dr Rank represents a foil of Nora in that he has had to face reality as it comes. Terminally ill, he is hopelessly in love with Nora. He also represents the cruelties of nature, since his disease was inherited from the excessive behaviors of his father. His character represents the inevitability of fate, and the sad reality of nature. When he leaves his last scene, he accepts his role as a recluse to life, and he leaves with as much sadness as he enters.
So what we basically have is that the character of Nora, immature, oblivious, belittled, and seemingly naive, is surrounded by characters with possible emotional and social control over her. In order for Nora to break free she would have needed to learn the realities of each of them, apply their lessons to her own life, and learn to face reality for what it is. Ultimately, that is exactly what she did. And she became free.