The mood of The Bridge of San Luis Rey is pensive, philosophical, and at times playful. The novel sets out very seriously to address big moral questions. Characters such as Brother Juniper are trying to figure out if it's possible to determine why some people suffer while others do not. Others, like the Perichole, lose loved ones in the bridge collapse have to learn how to live with grief and find meaning in random tragedies.
Because the narrative centers these problems, the reading experience is immediately a thoughtful one, with the reader exploring these questions alongside the characters. While the book doesn't provide any definitive answers to the questions he poses, it does emphasize the values he considers most important for living a meaningful life, namely selfless love and altruism. The combination of open-ended questions and strong assertions about living a good life emphasize that the novel has something to teach its readers, and thus contributes to the philosophical mood.
At the same time, the novel is often very funny. This is especially true when the narrator employs a sardonic tone to depict the 18th century from a 20th-century perspective. The narrator frequently mocks colonial Peruvian customs, politics, and even dress, referring to Doña Maria's childhood outfit as a "harness of jewels." These comments create a sense of play in the narrative and provide some emotional respite from the novel's deep philosophical concerns. Ultimately, in creating a mood that vacillates frequently between humor and grave seriousness, the novel communicates that to an astute observer, everyday life provides plenty of moments to ponder and laugh at.
