An allusion is a casual reference to another work of literature, a historical event, a piece of popular knowledge, etc. “The Purloined Letter” contains several. Dupin uses allusion to explain his methods of solving the case. He begins by alluding to the physician John Abernethy while speaking to emphasize the importance of taking advice. He also alludes to Rochefoucauld, La Bruyère, Machiavelli, and Campanella. He quotes and references the French cynic Chamfort, saying, “Il y a parier […] que toute idée publique, toute convention reçue, est une sottise, car elle a convenu au plus grand nombre” (It is safe to wager that every idea that is public property, every accepted convention, is a bit of stupidity, for it has suited the majority) (17). These allusions highlight Dupin’s intelligence and unconventional methods of investigation. Some also hold thematic significance; for example, Machiavelli is best known for his discussion of how rulers should maintain their authority—i.e., The Nature and Exercise of Power.

Dupin himself provides an explanation of his use of analogy—a kind of extended metaphor typically used to illustrate a point—when he states that “[t]he material world […] abounds with very strict analogies to the immaterial; and thus […] metaphor, or