More than other tales by Poe, “The Cask of Amontillado” is a study in opposites. The setting is Italy during Carnival, a time of joy and revelry. The warm Mediterranean lands seem to have held a special position in the hearts of English and American writers of the nineteenth century. Here was a place where there was a kind of freedom, a contrast to the cold and strait-laced anglophone world. Fortunato is one of the revelers, wearing “motley,” a clown's muticolored outfit with a conical cap adorned with jingling bells. He is also drunk. The appearance of Montresor's victim is one of innocent playfulness, hardly that of a man who has inflicted the thousand injuries Montresor claims and which are the motive for the gruesome revenge he carries out.

The central subject of the tale is alcohol as much as it is vengeance. Not only is Fortunato under the influence, but the bait Montresor devises for him is wine. The catacombs themselves contain an opposition of ideas. A wine vault, the place where the valued intoxicants and the ecstasy they promise are stored, is located amid the bones of the dead. “We had passed through walls of piled bones,” Montresor says, “with casks and puncheons intermingling, into the inmost recesses of catacombs.” It's a paradoxical setting, but one that reflects Montresor's point of view relating to the man he plans to kill. The behavior of the men to each other suggests that they are, in fact, the closest of friends, though from Montresor's standpoint they are enemies. Montresor hates Fortunato enough to kill him, and to kill him in a particularly sadistic fashion. In spite of this, he continues to refer to him as a friend—actually, as “my poor friend,” when Fortunato, besides being intoxicated, is seized by a horrible fit of coughing as they journey through the damp vault.

The question of friendship or brotherhood is emphasized in an exchange between them about freemasonry. The “gesticulation” by Fortunato, which Montresor does not understand, is evidence of Fortunato's being a mason and knowing a secret sign. Montresor, to Fortunato's surprise, tells him that he belongs to the order as well, and as an indication of this, he shows him the trowel he has been carrying under his coat. This is the instrument he will use to build the wall of Fortunato's tomb. It thus symbolizes both the brotherhood of the order, and death.

The scene also shows the schizoid nature of the “friendship” between the two. If they are close friends, as Montresor asserts and as Fortunato's trusting attitude to him would indicate, it's odd that Fortunato would have any doubt about Montresor's status with regard to the masonic brotherhood. One would think he would either know Montresor is a mason or know he isn't one. The exchange about freemasonry appears to have little relevance to the action, but it is typical of Poe to add incidental bits of irrationality to a narrative. It enhances the atmosphere of surprise and contradiction that permeates the story.

Fortunato, significantly, does not even seem to react when Montresor leads him into the makeshift tomb and chains him to the wall. One would think that even a drunken man would attempt to fight back. “He was too much astounded to resist,” Montresor says. Fortunato's only words at this point are “The Amontillado.” The narration of this sequence is so rapid and even perfunctory that what is taking place at the moment might escape the reader. Before one even knows what has happened, the reader, just like Fortunato, is confronted with Montresor suddenly busying himself with stone, mortar, and trowel and walling up his “friend” alive.

Poe's method of telling this is understated, nonchalant in a way that differs from the accounts of murder in most of his oeuvre. Again, there is a contrast, a disconnect between the cruelty of the scene and the indifferent manner in which it is described. The behavior of both Montresor and that of his victim is surreal. Fortunato regains his sobriety, according to Montresor, but still does not question why Montresor is doing this to him. His only direct plea for his life is the desperate exclamation, “For the love of God!” That Montresor repeats this to him perhaps indicates he believes his mission of killing Fortunato is divinely sanctioned, though it's more likely he is being ironic. Yet the reader still knows nothing of the real reason Fortunato is being killed. The “thousand injuries” and the “insult” he has supposedly inflicted upon Montresor are not described in any detail, or described at all. From the point of view of Poe's literary technique, this isn't surprising.

Whatever Fortunato might have done, it could not justify murder, even for revenge, especially this kind of murder. But Poe's forcefulness as a writer is rooted in the mystery he creates, the alternate universe in which reason is invalidated and nothing makes realistic sense. A murder, or any kind of cruelty, is more powerful and fascinating if the reason for it is unspoken. When there is no reason at all for it, the murder becomes an emblem not only of the contradiction at the bottom of the human soul between good and evil, but of a meaninglessness at the heart of existence. Montresor, like Macbeth, kills without cause. Montresor's “unreliability” as narrator is a partial explanation for his actions, since so far as we can tell he may be suffering from psychotic delusions. But beyond this, the dreamlike atmosphere of the story, as with Poe in general, raises the question of what, if anything, is “real,” in anyone's perception, and what is imagined. These opposites, reality and illusion, are the basis of “The Cask of Amontillado,” but they are opposites merged into an unexplained and bizarre totality of a strange nightmare.