Deception
B. F. Pinkerton is almost completely amoral. He believes that he is not really bound by laws, morality, or anything else except in his own country. Arrogant to the core, Pinkerton abandons Butterfly with no regard for her well-being. Thus, a major theme in the opera is deception, because we watch as Pinkerton creates a set of promises and expectations for his Japanese wife, Butterfly, only to completely betray her.
On another level, the opera is about deception on a broader level. Every character participates in a deception to a certain extent. The initial matchmaking that Goro orchestrates is built around a lie—that Pinkerton is actually marrying Butterfly rather than just looking for a way to have sex in another country. Then, all of the characters, including those who find Pinkerton's behavior reprehensible, are complicit in upholding the deception. Sharpless, who worries that Pinkerton's actions are harmful, cannot bring himself to bring Butterfly down to earth, and so participates in his own form of deception. Finally, Butterfly herself engages in self-deception, choosing to believe that Pinkerton will return, even when there is overwhelming evidence to the contrary.
Injured innocence
Butterfly, a Japanese girl who is only 15 years old, is completely innocent of the hardship she may face in marrying an American man. When she goes to marry him, she imagines that she is the happiest girl in the world, and seems to have taken no emotional precautions in giving her heart to another. Her naive faith in her husband and willingness to Americanize herself leads to her undoing. She is trusting and faithful to the end, despite the fact that all signs point to the fact that she has been deceived. Thus, we see that a major part of the thematic narrative of the opera is the image of a young girl whose naivety is exploited. Indeed, even her name, "Butterfly" points to her delicacy and fragility, a metaphor for the ways that, even though she is special and exquisite, she is susceptible to getting terribly injured emotionally.
Honor
As portrayed in the opera, Japanese and American cultures have radically different ideas of honor. Butterfly's family disowns her chiefly because, by marrying an American and forsaking her ancestral gods, she has done a "dishonorable" thing. However, Butterfly regards marriage as perfectly honorable and appropriate, and believes that Americanizing herself from a religious and cultural perspective is the only honorable and appropriate thing to do. She also waits patiently and faithfully for her husband, doing what she thinks is the honorable thing as the money runs out and her options narrow, instead of remarrying and providing for her son.
At the end of the opera, Butterfly recognizes her mistake and realizes that the only way to preserve her honor is to commit suicide. She reads the inscription on her father's dagger, which reads, "Let him die with honor who cannot live with honor." Having not been able to live honorably, having been deprived of it by poverty and her faulty marriage, Butterfly chooses to die honorably instead.
American entitlement
Pinkerton's lack of sensitivity can be understood partially as the follies of an unaware man just looking to have a sexual affair, but it must also be read as reflecting their different racial and ethnic backgrounds. Pinkerton is a white Army lieutenant using the looseness of Japanese law in order to have a fling with an unsuspecting Japanese girl. Butterfly is a desperate young girl from Japan looking for a stable and prosperous life, and sees a marriage to a wealthy American as redemptive. In this way, their imbalanced expectations are connected to their respective national identities. Pinkerton's belief that he can toy with a woman's heart without consequence reflects his sense of colonial entitlement and an implicit racial superiority that is central to the themes of the play.
Delusion
Throughout the opera, people try to talk sense into Butterfly. Her uncle does not want her to go through with the marriage, and many people tell her that foreigners like Pinkerton always abandon their Japanese wives. Yet for some reason, Butterfly believes her situation is different. Because Pinkerton promises not to harm her, she trusts him. By marrying him and converting to Christianity she earns the contempt and rejection of her family, who might otherwise have helped and supported her if her marriage ended badly.
Everyone but Butterfly can see that her marriage is a sham, and many people try to help her both before and after. Even Sharpless, who as an American consul has no particular duty to help Butterfly, attempts to help her move on after Pinkerton's departure. He serves as a go-between between Butterfly and her husband and attempts to get Pinkerton to do the honorable thing, but every time he tries to break the news to Butterfly, she cuts him off. In this way, we see that Butterfly desires to stay "in the dark," deluding herself that she has made a wise decision to stay with Pinkerton.
Love
While the marriage proves to be a complete sham, Butterfly and Pinkerton do share a kind of love. In the first act, Pinkerton privately discusses his intentions to end the marriage prematurely, but when he sees how vulnerable Butterfly is, provides her with words of comfort and love. At the end of the first act, they both speak tenderly to one another as if they will always care for one another, and embrace lovingly. While there is a misunderstanding between the two of them about how steadfast their love will be, the emotion of their duet suggests that the love they share is strong, even if Pinkerton's is more sexual and momentary than anything.
For Butterfly, love is about loyalty (to the point of delusion) and she proves her devotion to Pinkerton by remaining true to him even when it seems as though he has betrayed her. She sees their contract as everlasting, and performs her love by remaining faithful.
Cultural assimilation and conversion
In order to show her devotion to Pinkerton, Butterfly converts to Christianity, an act that leads her family to renounce her as being disloyal to her culture. In the opera, Butterfly chooses to convert and change her own cultural identity for a man—a choice that comes at a huge expense. It is not until she realizes that this act of devotion was all in vain that she can remember her own authentic cultural identity as a Japanese woman. At this point, she chooses to die in the honorable Japanese fashion, by committing ritual suicide.
