Righteousness
Righteousness—the quality of being correct and justified in one's morality—is a dominant theme in "Rain." Early in the story, the narrator comments on how the Macphails and the Davidsons found agreeable company in each other on the steamer ship because they shared a moral aversion to the passengers gambling and drinking onboard. As missionaries, the Davidsons' righteousness informs their aim to convert indigenous Samoans to Christianity. When Davidson learns of Miss Thompson's sinful life as a sex worker, he assumes authority over her "lost soul" and endeavors to make her repent. He also wishes for her to suffer, believing it a necessary punishment for her sinful behavior. However, the strict moral code Davidson lives by is what leads him to commit suicide after attempting the sin of adultery.
Privacy
In contrast to the missionary couple's belief that it is their duty to dictate what others do, Dr. Macphail is a proponent of an individual's right to privacy. Upon first hearing the gramophone and male voices coming from Miss Thompson's room, Dr. Macphail unsuccessfully attempts to head off Davidson's inquisition by talking "rather prosily" about his time serving as a medic in Flanders. When Davidson realizes that Miss Thompson is a sex worker and announces he will stop her, Macphail tries to dissuade him. Later, after the men in the woman's room push Davidson out, Macphail remarks to his wife, "Why couldn't he mind his own business?" The theme of privacy arises again when Macphail advocates for Miss Thompson despite a desire to stay out of the matter and leave her alone. When she expresses a fear of returning to San Francisco, Macphail doesn't ask why. When Davidson wants to know, Macphail bluntly replies: "I didn't inquire. ... And I think one does better to mind one's own business." Ultimately, Davidson's disregard for privacy leads to his peril: If he had never involved himself in Miss Thompson's business, he would not have transgressed against his own moral code and might have left Pago Pago alive.
Condescension
Condescension—a patronizing attitude of superiority—is another key theme in "Rain." Along with a righteousness informed by their religious convictions, the Davidsons adopt an insulting attitude of superiority toward the native inhabitants of Samoa. The theme first arises when Dr. Macphail and Mrs. Davidson stand at the boat railing together and Mrs. Davidson criticizes the traditional lavalava garments the Samoans wear and speaks proudly of how she and her husband have outlawed traditional dancing in their district of islands, arguing that it leads to immorality. Implicit in her condescending attitude is a disregard for Samoan culture that is informed by racism and colonialism. Having known only her own subjective experience of the world, Mrs. Davidson assumes the white Christian culture she was raised in is superior to all others.
Hypocrisy
Hypocrisy—the practice of not conforming to the moral standards one claims to have—is another major theme in "Rain." From the outset of the story, the Davidsons brag with passionate conviction about their accomplishments as missionaries who have successfully instilled a sense of sin into the local Samoan culture in their district. Having been horrified by what they saw as immoral behavior (and what the Samoans merely understood as natural), the Davidsons sought to extinguish the comfort and freedom from Samoans' lives and kindle a new fear of a punishing Christian God. Davidson takes the same approach with Miss Thompson, grinding down her will by isolating her in the boarding house and threatening to send her back to San Francisco to serve the prison sentence she evaded. Even though she repents, Davidson insists that suffering punishment is necessary for the salvation of her soul. The theme of hypocrisy arises suddenly at the end of the story when Dr. Macphail understands that Davidson killed himself because he tried to have sex with Miss Thompson, his obsession with her having proved to be about more than her saving soul. After realizing the hypocrisy of breaking his own moral code, Davidson sought to punish himself for his sin by ending his life in disgrace.
