Poe defines Dupin's method, ratiocination, using the example of a card player: "the extent of information obtained; lies not so much in the validity of the inference as in the quality of the observation."[12][13] Poe then provides a narrative example where Dupin explains how he knew the narrator was thinking about the actor Chantilly.[14][15] Dupin then applies his method to the solving of this crime.
Dupin's method emphasizes the importance of reading and the written word. The newspaper accounts pique his curiosity; he learns about orangutans from a written account by "Cuvier" — likely Georges Cuvier, the French zoologist. This method also engages the reader, who follows along by reading the clues himself.[16] Poe also emphasizes the power of the spoken word. When Dupin asks the sailor for information about the murders, the sailor himself acts out a partial death: "The sailor's face flushed up as if he were struggling with suffocation... the next moment he fell back into his seat, trembling violently, and with the countenance of death itself."[17]