The Wild Duck's thematic duality — reality versus idealism — becomes a structural feature of the play. Each scene illustrates this dualism. First Gregers confronts his father, a realist, and accuses him of a life built on lies and deception. In the following scene, Gregers confronts Hialmar and begins to rescue his friend from a life of self-delusion. Act III represents the antagonism between the realist Relling and young Werle, while Act IV exposes the paradox between Gregers' principles and the impossibility of realizing them. In the final scene, the duality becomes rationalized with Hedvig's suicide indicating the failure of applying pure principles to inappropriate situations. In effect, Ibsen concludes that life is a dynamic process whose only truth is based on any system which supports an individual's will to survive; life cannot exist according to principle but according to a compromise between emotional needs and the environment.
The central symbol of the play — an image borrowed from romanticism — further illustrates this duality. Ironically Ibsen uses it to destroy the very romanticism he describes in his characters. In a little poem called "The Sea Bird," written by Welhaven, one of Norway's most famous romantic poets, a wild duck dies from the shot of a careless hunter and dives silently to the bottom of the sea. Halvdan Koht, an Ibsen biographer and renown scholar, expresses one aspect of the double-viewed meaning of the symbol: The broken-winged duck [he writes] which gathered around it the dreams in the Ekdal home sent a strange tremulous flute note into the harsh, cold realism which otherwise gave such a sinister air to the play.
The "sinister air" Koht refers to is the resolution between the shabby, unromantic atmosphere of Ekdal's household and Hialmar's fantasy life expressed by the wilderness hunting ground in the garret, the hopes of Hedvig and their realization, and Ekdal's imitative life-values with his imaginary invention. Ibsen furthermore expresses the paradoxical nature of life with his use of humor. Although the Ekdal household is a tragic one, eventually sacrificing Hedvig to Hialmar's personal emptiness, the comedy of the situation is unmistakable and serves to heighten the seriousness of Ibsen's theme. Hialmar's affections, his poses, his ridiculous interest in richly buttered bread and cold beer are not in themselves funny; these qualities underscore the pathetic mediocrity of his character. Gregers Werle, as well, ascetic and grimly serious about his "life's mission," is ridiculous when he proves his worldly ineptness by smoking up his room from a badly-fired stove, then flooding the floor to douse the fire. Molvik, the romantic clergyman who saves face by considering himself "demonic" is a funny character. Again this humorous quality serves a serious purpose. With Molvik, Ibsen ironically subverts the efficacy of Relling's romantic remedies of the "life-lies": at the side of Hedvig's corpse, Molvik's inappropriate declamation, "the child is not dead but sleepeth," underscores the pathetic futility of trying to avoid, by various methods, the tragic consequences of human frailty.
Using humor as a technique to indicate the tragic paradox between living according to principles of reality or ideality, and using dialogue and situations to underline the duality, Ibsen's The Wild Duck shows that life-truths are dynamic processes which sustain individuals according to their human weaknesses. According to this system, "life-lies" are life-truths, an idealistic point of view leads to self-deception, and "truth" is whatever belief an individual requires to sustain life.