Abstract Modern mystery writers are indebted to Edgar Allan Poe (1809-1849). Although he is primarily known for his horror stories, Poe also wrote a series of what he called, “tales of ratiocination,” which helped define the conventions used in Arthur Conan Doyle’s Sherlock Holmes detective stories, and which helped influence the development of the modern mystery. One of Poe’s most popular detective stories is “The Purloined Letter” (1844). As with the other stories that feature C. Auguste Dupin, Poe’s famous detective protagonist, “The Purloined Letter” emphasizes the use of deductive reasoning – a specific type of logic that examines all factors in a case objectively – to solve mysteries that have stumped others. In the following essay, an attempt has been made to discuss Poe’s theory of the “bi-part soul” and its application in his “The Purloined Letter”. Key Words: Edgar Allan Poe, “The Purloined Letter”, “Bi-part” soul, logic, imagination, reason.