Themes are the fundamental and often universal ideas explored in a literary work.

The "claim of the Ideal" and the "life-illusion"

The play distributes these competing doctrines between the rivals Relling and Gregers, two "spiritual doctors" in conflict over Hialmar's destiny. Gregers's claim of the ideal relies on his belief that the soul must bring itself into the light and attain truth at all costs. Thus Greger preaches forgiveness, exaltation, redemption, martyrdom, confession, absolution, and sacrifice in spite of the ruin he brings to the Ekdal household.

In contrast, Relling speaks in terms of pathology, replacing Gregers's spiritual diagnoses Gregers with quasi-medical/psychological ones. This turn to psychology is one of the defining aspects of Ibsen's drama. Hialmar is not in spiritual tumult but suffers from illness. Gregers himself suffers from an "integrity- fever" and a "delirium of hero-worship." His "claim of the ideal" becomes a disorder rather than a moral or spiritual imperative. The ideal does not figure as some moral or spiritual imperative but is yet another pathology, as closely related to the lie as typhus is to putrid fever. What is imperative for Relling then is not the soul's attainment to truth but the treatment of mental disorder. Both men require a remedy, the "stimulating principle" of illusion. Hialmar can dream of his invention and sustain the faith of his family and the mirage of his happy household, and Ekdal can hunt in the garret.

The Romantic Hero

In The Wild Duck, the romantic hero—who finds his comic double in the fickle, melodramatic Hialmar—is most explicitly demystified in the exchange between Relling and Gregers in Act V. Hialmar's handsomeness, "superficially emotional temperament," "sympathetic voice," and talent for declaiming the verses and thoughts of others have always made him appear the "great light of the future" within his personal circles. The play debunks this fantasy of idolatry throughout. The play also critiques the romantic hero by parodying his notions of creation and creativity. Though Hialmar cannot explain his invention at the moment, he is certain it will come. He only awaits inspiration.

Ibsen also unmasks the romantic hero by underling the everyday affairs of his household. The ever-practical Gina, who runs the household affairs, will methodically tabulate the day's expenses; Gina and Ekdal will fret about the rental of the spare room; and much of the action will revolve around domestic comforts, such as the serving of food. Such moments of domesticity function to ironize the lofty, romantic figure Hialmar would cut.

The Myth of the Fathers

The struggle with the figure of the father propels the action of the play. First, an almost mythically enigmatic crime committed by its two patriarchs, Werle and Ekdal, lurks in the backdrop, mysteriously establishing the relations between the two families. Thus Ekdal describes the tragedy that ultimately ensues as the woods revenge for this unspoken crime.

Within the fantasies of the sons, Werle figures as the "bad daddy" and Ekdal the good one. In fantasy, and Gregers's fantasy above all, Werle is a primal father, perverse and tyrannical, who intervenes freely into the sons' household. Thus the shadow of Werle supplants Hialmar as father and provider. Moreover, this fantasy Werle is guilty for ruining the rival patriarch, the good and, importantly, idealized Ekdal. Retrospectively Ekdal appears the brave lieutenant and stalwart hunter; undoubtedly his ruin makes this idealization all the more possible.