The Chilterns share their own moment of bliss, and Lord Goring finally asks for Mabel's hand in marriage. On account of his discovery of Mrs. Cheveley at Goring's last night, however, Sir Robert cannot consent; Goring is left silent. Dramatically, Lady Chiltern thus reveals that Lord Goring expected her in his drawing room last night and that she authored the pink note as a request for his assistance. All reconcile, and Lady Chiltern writes Sir Robert's name at the top of her "love letter."
Mabel and Caversham then enter and, much to the latter's surprise, she announces her engagement with Goring. Caversham commands his son to be for Mabel an ideal husband at the risk of disinheritance; jokingly, Mabel recoils. "An ideal husband!" she exclaims. "Oh, I don't think I should like that. It sounds like something in the next world." Goring can be what he likes; Mabel, overcome, only wants to be a "real wife" to him.
All exit except for Sir Robert, who sits alone pensively as at the end of Act I. Lady Chiltern returns, and he asks if she loves or merely pities him. Lady Chiltern pledges her love and the beginning of a new life for them both.
As with the popular domestic comedies upon which An Ideal Husband is based, Act IV brings us to a culminating restoration of married life. All is set right: Sir Robert preserves his public image and indeed even advances in his career; the Chilterns' reunite; the young lovers, Goring and Mabel, come together as well. Rather than adhere strictly to a model of rising, climatic, and falling action, the act concludes the play with a series of dizzying complications—a misread note, a complex choreography of entrances, exits, and private conversations, confessions—that only resolve themselves at the very end.
As we recall from Act III, Lady Chiltern naïvely writes her note to Goring as a plea for help: "I want you. I trust you. I am coming to you." Notably, Mrs. Cheveley mocks this pink note as resembling the start of some "middle class romance," suggesting Wilde's self-irony regarding his use of this stock device. Ultimately it comes to serve as a sort of second marriage certificate, symbolizing, with the inscription of Sir Robert's name, a restoration of the Chilterns' married life. Though Goring jokingly moves to reclaim the letter, it is clearly no longer meant for him. This restoration of the conjugal household occurs on rather conventional moral terms. Once again, the language of melodrama intervenes: there is a profusion of exclamations, sighs, and somewhat trite appeals to faith, love, charity, devotion, and onward as characters succumb to emotion. Lord Goring especially delivers these pronouncements on conjugal bliss. In particular, he makes a rousing speech to Lady Chiltern upon Sir Robert's decision to withdraw from public life that establishes the proper roles of man and woman in married life. We will sketch it briefly here.
First, Goring argues that men and women alike are not worthy of sacrifices as terrible as the one Sir Robert faces. Lady Chiltern cannot allow Sir Robert to resign from public life especially, however, because Sir Robert is a man. Man's life remains of wider scope, deeper issues, and greater ambitions than woman's. Whereas a woman's life revolves in "curves of emotions," man's progresses in "lines of intellect." Consequently, women are not meant to judge men but to forgive them ("Pardon, not punishment, is their mission"). Thus Lady Chiltern must assume the role that defines Victorian womanhood in its most conventional form: that of a forgiving and anodyne caregiver.