This tragedy unfolds through a conflict between reason and emotion, with passion taking the lead. The main characters, when dealing with their sexual desires, fail to apply sound judgment. Lust overshadows all other considerations. Beatrice, in particular, displays considerable irony in how she justifies her changing feelings. She quickly falls for Alsemero, yet convinces herself that her decision is logical. She rationalizes leaving Alonzo by claiming her initial attraction was based on appearances and poor judgment. She even advises Alsemero on the importance of testing emotions like love with reason. However, in Act 1, she reveals her true feelings when she admits to a "giddy turning" in her affections as she shifts from Alonzo to Alsemero. This hardly reflects a mindset guided by rational judgment. In reality, Beatrice deceives herself, disguising her inconsistency as something else. She even convinces herself that Alsemero is a man of sound judgment because she approves of his choice of Jasperino as a friend: "It is a sign he makes his choice with judgement," she claims. She then believes that by choosing a man of good judgment, she demonstrates the same virtue: "Methinks I love now with the eyes of judgement, / And see the way to merit." However, Beatrice lives in self-deception, which she never questions. For example, in her interactions with De Flores, she fails to realize he desires more than just money from her, completely misjudging his character.

Alonzo, another character, also blinds himself to reality because of romantic or sexual desire. In Act 2, Scene 1, he doesn't recognize that Beatrice greets him without warmth and shows no interest. He ignores Tomazo’s warning simply because he cannot bear to hear anything negative about Beatrice, despite clear evidence of her indifference. Tomazo, one of the few characters in the play who retains sound judgment, as he is not influenced by love or passion, speaks a truth that the play ultimately reveals: “Why, here is love’s tame madness: thus a man / Quickly steals into his vexation.” He suggests that ignoring an uncomfortable truth due to love is madness, as it will soon lead to distress. For Alonzo, it results in more than distress—it directly leads to his death.

Diaphanta also suffers fatal consequences for letting passion override judgment. On Beatrice’s wedding night, she becomes too involved in Alsemero’s embraces and fails to return at the agreed time. As a result, she perishes in a fire.

De Flores is another character whose desires cloud his judgment. Unlike Beatrice, he sees the situation clearly and doesn't lie to himself. He knows Beatrice detests him, yet he still visits her whenever possible, enduring her harsh treatment. He realizes that, logically, his actions make no sense. However, his intense desire for Beatrice overshadows everything else. He confesses that he "cannot choose but love her," and that "I can as well be hanged as refrain from seeing her." De Flores has reached a point where he can no longer think sensibly; he is entirely overpowered by lust.

Once characters give in to love, passion, or lust, the resulting crimes seem inevitable.

The play vividly contrasts the difference between appearance and reality. Beatrice seems perfectly fine on the surface, but beneath her attractive exterior lies a selfish, ruthless, and violent personality. As the play progresses, she goes through several internal changes that starkly differ from her initial appearance. Initially, while engaged to Alonzo, she secretly loves Alsemero. Later, in the silent scene at the start of act 4, scene 1, she is depicted as a modest, virtuous bride in a solemn wedding procession. However, in truth, she is...