Ambivalence

Ambivalence might be an unexpected theme for a story in which a man's emotions and intent are one-sided to the point of burying another man alive, but the surface events conceal a deeper meaning. One cannot know precisely what motivates Montresor in his quest for revenge. Poe leaves the reader in the dark regarding the "thousand injuries" to which Montresor has been subjected. It's conceivable that Montresor suffers from paranoia and is under a massive delusion about Fortunato's treatment of him. He continues, through the narrative, to refer to him as his "friend." The impression is one of a man compelled to carry out retributive justice almost against his will. The final statement, "rest in peace," is ironic but perhaps the key to the entire story. If indeed this is an enemy he has killed, it's strange that this wish sums up his narrative.

An analogy in the Poe canon is "The Black Cat," in which the narrator declares that he killed Pluto with tears streaming down his cheeks because the cat loved him and had never done him any harm. The same is true concerning the elderly victim in "The Tell-Tale Heart." Poe alludes to the "perversity" that motivates his killers; it is just as accurate to describe the feeling that dominates these characters as a kind of bizarre, grand-scale ambivalence. They love and hate on an exaggerated, almost supernatural plane, in a kind of grotesque manifestation of the irrationality that lies at the heart of human behavior.

Self-Delusion

Montresor, whatever the reality or unreality of Fortunato's wrongs perpetrated against him, is duping himself. He begins with an extended statement, like a postulate, on the nature of vengeance and the proper way of enacting it against a foe. He says a wrong is "unredressed when the avenger fails to make himself felt as such to the one who has wronged him." Yet he never tells Fortunato why he's killing him. Not only does he not say what the specific wrongs committed against him have been, he gives no indication at all to the victim, even in the most general way, that revenge is what motivates him. Perhaps Montresor does not explain himself because there's nothing to explain. In any event, he appears to be under a delusion that he's been victimized, or at least in thinking that suffocating a man alive is the appropriate punishment for whatever Fortunato has supposedly done.

Fortunato has been deluded into thinking Montresor a friend. At no point until it is actually happening does he seem to suspect that Montresor intends to do him harm. Even after Montresor has led him into the niche and chained him, Fortunato's reaction is one of complete bewilderment. He seems to have no idea of what's taking place, or why.

Readers must be wary of overinterpretation on this point. Poe's main purpose, in a story such as this, may be simply to present a horrific occurrence that isn't intended to be looked into as more than an instance of grisly cruelty, a straightforward account of the potential for sadistic violence that is an unfortunate component of human nature. To read a further elaborate message into it runs the risk of attributing motives to Poe that were perhaps foreign to the unpretentious, non-didactic style of his fiction.

Substance Abuse

The theme of alcoholism and substance abuse in general is so prevalent and so natural in Poe that it can sometimes be overlooked. "The Cask of Amontillado" takes place during Carnival, a time of revelry and drunkenness. Not only is Fortunato drunk when Montresor lures him to the catacombs, but the bait is a cask of wine. Ironically, Fortunato seems to regain his sobriety, or at least, Montresor thinks he does. Nevertheless, it's unlikely that Fortunato would have been so trusting to begin with had he not been under the influence of alcohol.

Irrationality

Though Fortunato finally pleads, "For the love of God, Montresor!" until this point his reaction to being walled up alive has been muted, to say the least. He does not seem aware of what's happening, or to care. It defies human reason for even a drunken man to act this way. He may believe at first that the whole thing is a joke, as he says, "An excellent jest! We shall have many a rich laugh about it at the palazzo." But when he finally realizes he's being entombed, instead of asking Montresor, "Why are you doing this?" he makes an irrational plea to Fortunato's religious conscience.

The bizarre reactions of Fortunato are a mirror of Montresor's own irrationality. Regardless of whatever "injuries" may have been inflicted upon him, it's an understatement to observe that burying a man alive is an exaggerated and sadistic form of retribution.

Hypocrisy

Poe's exploration of hypocrisy occurs on several levels. Montresor is the ultimate hypocrite in presenting himself to Fortunato as a friend when, in reality, he hates him. He seeks revenge, but the honorable and honest way of achieving it, in the context of the time and place, would be to challenge him to a duel, or at least confront him openly in a less violent manner. Instead, he feigns amiability and takes advantage of the drunken state Fortunato is in to surprise him and kill him when Fortunato has no chance to defend himself.

The setting in which this takes place is symbolic of a kind of collective hypocrisy of the establishment to which Poe alludes elsewhere as well. It is very possible that the vault in which Montresor carries out his plan contains the bones of victims of the Inquisition. In both “The Pit and the Pendulum” and “The Black Cat,” the religious hypocrisy of the past is a backdrop, in the one case specifically in the story itself, and in the other, a reenactment which the narrator alludes to when he walls up the body of his murdered wife as “the monks of the Inquisition” did their victims. The catacombs in “The Cask of Amontillado” are an emblem of the religious hypocrisy of Europe's past and, as such, are the perfect setting for Montresor's cruelty.

Nihilism

A corollary of the theme of hypocrisy involves the story's alleged moral. Poe's works are at least implicitly nihilistic, given that he repeatedly shows the most amoral of characters acting out their fantasies without regard for the lives and feelings of others. At times, in “The Black Cat” and “The Tell-Tale Heart,” the killer is caught, and retribution, the reader is to understand, will follow. But in “The Cask of Amontillado,” the killer is never reprimanded. His own self-justification, as noted, is hypocritical, and Poe evidently intends it to be seen that way. But in any tale where a wrong is unredressed, the implied moral is that on some level, the wrong is justified and is therefore not a wrong at all. It is a kind of negation of morality, or at least a theme that anticipates the existentialist writers in showing the individual as the creator of his own system of right and wrong, rather than as a follower of religion and convention.