LORD CAVERSHAM: And if you don't make this lady an ideal husband, I'll cut you off without a shilling.
MABEL CHILTERN: An ideal husband! Oh, I don't think I should like that. It sounds like something in the next world.
LORD CAVERSHAM: He can be what he chooses. All I want is to be to be oh, a real wife to him.
LORD CAVERSHAM: Upon my word, there is a good deal of common sense in that, Lady Chiltern.
The title phrase, "an ideal husband," appears in the penultimate dialogue of Act IV as the last joke of the play. Mabel Chiltern and Lord Goring have just announced their engagement, and Lord Caversham—emblematic of an older generation of London Society—issues the threat quoted above to his dandified son. At the same time, Mabel and Goring have negotiated a union that dispenses with question regarding the ideal behavior of the married couple. As Mabel protests, the "ideal husband" belongs in heaven; Goring can be whatever he wants while she wants to be his real wife who decidedly belongs to this world. Indeed, throughout the play they have assumed an amoral pose, disparaging the demands of duty and respectability. Their union thus in a sense counterpoises that of the upright Chilterns, who have just reconciled and are also on the scene.
Humorously, Caversham concurs with his future daughter-in-law. His comment on "common sense" recalls a comic interlude from Act III, in which he identifies common sense as a property of men. Moreover, unbeknownst to him, he has addressed his comment to the character who above all has learned the dangers of attempting to create an ideal spouse, Lady Chiltern.