Her wager lost, Ida yields to Hilarion and bitterly asks Lady Blanche if she can resign her post with dignity. The delighted Blanche, who will succeed her as head of the university, assures her that she can. Ida laments the failure of her "cherished scheme," but King Hildebrand points out the fatal flaw in her logic:
If you enlist all women in your cause,And make them all abjure tyrannic Man,The obvious question then arises, "HowIs this Posterity to be provided?"Princess Ida admits, "I never thought of that!" Hilarion makes an emotional appeal, urging her to give Man one chance, while Cyril observes that if she grows tired of the Prince, she can return to Castle Adamant. Lady Psyche says that she, too, will return if Cyril does not behave himself, but Melissa swears that she will not return under any circumstances. Finally, Ida admits that she has been wrong, and declares that indeed she loves Hilarion, ending with a quotation directly from the Tennyson poem. All celebrate, (With joy abiding).