Wilder uses The Bridge of San Luis Rey to warn against the casual judgment of others. The book shows how both public opinion and careful study can miss the private truths that shape a person, making compassion a steadier response than judgment.

Several examples show how public perception can ignore private suffering. Lima treats the marquesa as its “jest,” erasing the thoughtful, heartbroken woman who writes letters filled with insight and grief. Even her posthumous rehabilitation as a literary genius, though well-intentioned and seemingly complimentary, fails to grasp the depth of the pain that motivated her letters: “To [critics] it seems impossible that Doña María should have put herself to the same pains to dazzle her daughter that most artists expend on dazzling the public […] missing (as most readers do) the whole purport of literature, which is the notation of the heart” (11). The actress Camila Perichole faces a similar distortion. The public cheers when she mocks the marquesa in improvised songs, yet they miss her insecurities and her uneasy climb toward respectability. These portraits show how surface impressions hide the inner struggles of both women.

Brother Juniper’s project furnishes additional evidence of the difficulty of truly knowing another person. He spends six years gathering “thousands of little facts and anecdotes and testimonies” about the victims of the bridge collapse (6). However, his data never reaches the “central passion[s]” in the victims’ lives, and the failure lies in part in the fact that his aim is quite explicitly to judge his subjects. Much as he earlier attempted to rate plague victims on charts of “Goodness” and “Piety,” he now seeks to understand the deaths caused by the bridge collapse in terms of reward or punishment. However, the victims’ lives are not marked by such clear moral patterns, as even he dimly senses; he characterizes several of the deaths as punishment for sin but privately reflects that “It was just possible that the Marquesa de Montemayor was not a monster of avarice, and Uncle Pio of self-indulgence” (78). Indeed, the novel says relatively little about the marquesa’s wealth or Uncle Pio’s libertinism. Instead, it shows how the marquesa’s love for her daughter, far from pious, leads her toward a last act of courage, and how Uncle Pio’s devotion to Camelia persists despite her pride, scorn, and insults. Brother Juniper’s story thus demonstrates that it is possible to know almost everything about a person’s life yet still misunderstand their inner worlds, which do not collapse into tidy moral patterns.

The novel extends this problem to intimate relationships. Esteban and Manuel live with a shared identity but in some ways do not understand one another: Esteban, who is exclusively devoted to his brother, cannot help but feel that Manuel’s feelings for Camila constitute a betrayal, while Manuel, who takes his devotion to his brother as a given regardless of other attachments, cannot understand why Esteban would feel this way. Each understands the fact of the other’s emotions, but neither can fully inhabit those emotions because of fundamental differences in the way they think and feel. These moments show how even those who live close to one another cannot fully grasp another person’s interior life, which makes firm judgment impossible.