Throughout The Bridge of San Luis Rey, letters and the act of writing form a motif that represents both the power of art for confronting philosophical questions and its inevitable limitations.
Doña Maria's letters to her daughter, Doña Clara, are perhaps the most important written documents in the novel. Doña Maria writes the letters in hopes of eliciting affection from a daughter who dislikes her and, by marrying a Spaniard, has sought to live as far from her as possible. Because Doña Maria's unrequited love for her daughter causes her to behave eccentrically, she shunned by her society during her lifetime; even Doña Clara, to whom the letters are lovingly addressed, seems to disregard them. However, the narrator frequently states that Doña Maria's son-in-law is secretly preserving their letters, and that when published after her death, they will become a national literary treasure. While no one recognizes Doña Maria's literary talent during her lifetime, the letters allow Doña Maria to express her feelings in a way that transcends the social constraints of her era.
At the same time, the narrator suggests that there's a note of falsity in most of Doña Maria's letters, noting that "many critics have accused her of keeping one eye on posterity." To the narrator, the letters are compromised because they contain an element of narcissism: Doña Maria is writing not simply to express love for her daughter, but to elicit love and approval in return. Only during the last days before the bridge collapse, when Doña Maria finally makes peace with her inability to singlehandedly change her daughter or their relationship, does she write "what she called her first letter," the only writing she produces that is free of ulterior motives. Doña Maria's trajectory as a letter-writer thus reflects her moral development and the final enlightenment she achieves before dying in the bridge collapse.
In other moments during the novel, characters' private writings emerge as an alternative to recognized "great" works of art. For example, Uncle Pio venerates the established masters of Spanish literature such as Cervantes or Tirso de Molina. He himself yearns "to make verses" and laments that he can never write as they do. He believes that the humorous ditties he writes for his own amusement are vastly inferior to the works of these great artists. However, the narrator says that Uncle Pio's writing eventually becomes "folk-music" and "have been born everywhere along the highroads"—in other words, Uncle Pio's work becomes part of the Peruvian tradition in a way that Cervantes and Tirso de Molina simply aren't. In this instance, Uncle Pio's humble musical output proves just as vital to the nation's culture as more conventional forms of art.
At the same time, some of the novel's most important characters—namely, the Perichole—are illiterate. In the most difficult moments of her life, the Perichole must employ Manuel to write letters on her behalf because she cannot do so herself. Even though she can't write as Doña Maria or Uncle Pio do, her ability to express herself is equal to theirs. Moreover, her confrontations with the great moral challenges of her life, such as the death of her son Jaime in the bridge collapse, are no less profound for being mediated by a scribe. While the novel elevates the humble, intimate acts of letter- and song-writing to the status of great art, it also emphasizes that people don't need to be able to write in order to wrestle with important philosophical questions.
