While describing his beloved Ligeia near the beginning of the short story of the same name, the narrator waxes poetic about his time spent interacting with her prior to her death. In doing so, he uses a simile comparing her to a shadow and metaphorically suggests that she is made of "marble":
I would in vain attempt to portray the majesty, the quiet ease, of her demeanor, or the incomprehensible lightness and elasticity of her footfall. She came and departed as a shadow. I was never made aware of her entrance into my closed study save by the dear music of her low sweet voice, as she placed her marble hand upon my shoulder. [...] It was the radiance of an opium dream—an airy and spirit-lifting vision more wildly divine than the phantasies which hovered about the slumbering souls of the daughters of Delos.
In the quote above, Ligeia is described as a “shadow,” as “marble,” and as having the “radiance of an opium dream”—in other words, in her death she has been transformed from a flesh-and-blood lover to an idea on a pedestal, an otherworldly entity. The narrator’s extreme devotion to this idealized figure, at the expense of remembering her humanity, is the first of many signs of his increasing madness.
In “The Murders in the Rue-Morgue,” Dupin uses the metaphor of a person looking at a star with peripheral vision to elucidate the problem with police detective work that focuses too much on the small details, thereby missing the overarching picture:
The modes and sources of this kind of error are well typified in the contemplation of the heavenly bodies. To look at a star by glances — to view it in a side-long way, by turning toward it the exterior portions of the retina (more susceptible of feeble impressions of light than the interior), is to behold the star distinctly — is to have the best appreciation of its lustre — a lustre which grows dim just in proportion as we turn our vision fully upon it.
This metaphor encapsulates how Dupin views the act of crime-solving as a beautiful mind exercise rather than having a solely moral imperative. The elegance and sophistication of his language, as he discusses “heavenly bodies” and their “lustre” and the capabilities of the human retina, is indicative of a man more preoccupied with aesthetics than actual ethics. “The Murders in the Rue-Morgue” is considered the first modern detective story in literature, and this story’s view and approach to crime-solving as a puzzle later became a staple of the genre.
At the end of “The Black Cat,” the narrator concludes his account with a final, exclamatory lament that his hubris ended up resulting in his own downfall. In doing so, he uses a metaphor to express just how large a mistake he made:
[...] a dozen stout arms were toiling at the wall. It fell bodily. The corpse, already greatly decayed and clotted with gore, stood erect before the eyes of the spectators. Upon its head, with red extended mouth and solitary eye of fire, sat the hideous beast whose craft had seduced me into murder, and whose informing voice had consigned me to the hangman. I had walled the monster up within the tomb!
On a surface level, the “monster” the narrator refers to is the black cat trapped within the wall of his home that sits upon the corpse of his wife. However, beyond simply calling the animal he despises a monster, the narrator’s claim that he “walled the monster up” also serves as a metaphorical expression of his own guilt over his violent, murderous actions earlier in the story. By literally walling up the evidence of his brutality, he hoped to hide his guilty conscience. Unfortunately for the narrator, when the wall comes tumbling down, so too does the veneer of his civility and humanity, and his monstrosity is exposed for all to see.
Dupin uses metaphors to explain his logical thought processes in “The Purloined Letter”:
"There is a game of puzzles,” he resumed, “which is played upon a map. One party playing requires another to find a given word—the name of town, river, state or empire—any word, in short, upon the motley and perplexed surface of the chart. A novice in the game generally seeks to embarrass his opponents by giving them the most minutely lettered names; but the adept selects such words as stretch, in large characters, from one end of the chart to the other.
In the passage above, Dupin compares the mysterious case of the purloined (i.e. stolen) letter to that of a puzzle game involving a map. Using this metaphor, Dupin is able to demonstrate the differences between his thinking and the common detective methods of law enforcement officials. Implicit in this metaphor is his belief that the policemen are behaving like novices, while he himself is the “adept” player. He continues, explaining the strategy of the more experienced player in further detail:
These, like the over-largely lettered signs and placards of the street, escape observation by dint of being excessively obvious; and here the physical oversight is precisely analogous with the moral inapprehension by which the intellect suffers to pass unnoticed those considerations which are too obtrusively and too palpably self-evident. But this is a point, it appears, somewhat above or beneath the understanding of the Prefect. He never once thought it probable, or possible, that the Minister had deposited the letter immediately beneath the nose of the whole world, by way of best preventing any portion of that world from perceiving it.
With these words, Dupin easily demonstrates the simplicity of his detective methodology in comparison to the complicated maneuvers of the police force. His ability to think deeply and then render complicated concepts with the simple metaphor of a game reveals his total mastery of the subject, allowing the crime-solving to continue with renewed invigoration.
