Along with “The Murders in the Rue Morgue,” “The Purloined Letter” establishes a new genre of short fiction in American literature: the detective story. Poe considered “The Purloined Letter” his best detective story, and critics have long identified the ways in which it redefines the mystery genre—it turns away from action toward intellectual analysis, for example. As opposed to the graphic violence of “The Murders in the Rue Morgue,” which features bodily mutilation and near decapitation by a wild animal, “The Purloined Letter” focuses more dryly on the relationship between the Paris police and Dupin, between the ineffectual established order and the savvy private eye. When the narrator opens the story by reflecting upon the gruesome murders in the Rue Morgue that Dupin has helped to solve, Poe makes it clear that the prior story is on his mind. Poe sets up the cool reason of “The Purloined Letter” in opposition to the violence of “The Murders in the Rue Morgue.” The battered and lacerated bodies of “The Murders in the Rue Morgue” are replaced by the bloodless, inanimate stolen letter. However, just as the Paris police are unable to solve the gory crime of passion in “The Murders in the Rue Morgue,” they are similarly unable to solve this apparently simple mystery, in which the solution is hidden in plain sight.
Poe moves away from violence and action by associating Dupin’s intelligence with his reflectiveness and his radical theories about the mind. This tale does not have the constant action of stories like “The Cask of Amontillado” or “The Black Cat.” Instead, this tale features the narrator and Dupin sitting in Dupin’s library and discussing ideas. The tale’s action, relayed by flashbacks, takes place outside the narrative frame. The narrative itself is told through dispassionate analysis. The intrusions of the prefect and his investigations of the Minister’s apartment come off as unrefined and unintellectual. Poe portrays the prefect as simultaneously the most active and the most unreflective character in the story. Dupin’s most pointed criticisms of the prefect have less to do with a personal attack than with a critique of the mode of investigation employed by the police as a whole. Dupin suggests that the police cannot think outside their own standard procedures. They are unable to place themselves in the minds of those who actually commit crimes. Dupin’s strategy of solving crimes, on the other hand, involves a process of thinking like someone else. Just as the boy playing “even and odd” enters his opponent’s mind, Dupin inhabits the consciousness of the criminal. He does not employ fancy psychological theories, but rather imitates the train of thought of his opponent. He succeeds in operating one step ahead of the police because he thinks as the Minister does.
This crime-solving technique of thinking like the criminal suggests that Dupin and the Minister are more doubles than opposites. The revenge aspect of the story, which Dupin promises after the Minister offends him in Vienna, arguably derives from their threatening similarity. Dupin’s note inside the phony letter, translated “So baneful a scheme, if not worthy of Atreus, is worthy of Thyestes,” suggests the rivalry that accompanies brotherly minds. In the French dramatist Crébillon’s early-eighteenth-century tragedy Atrée et Thyeste (or Atreus and Thyestes), Thyestes seduces the wife of his brother, Atreus. In retaliation, Atreus murders the sons of Thyestes and serves them to their father at a feast. Dupin implies here that Thyestes deserves more punishment than Atreus because he commits the original wrong. In contrast, Atreus’s revenge is legitimate because it repays the original offense. Dupin considers his own deed to be revenge and thereby morally justified.