In The Cask of Amontillado, Montresor traps Fortunato in the catacombs, but his motives are not explicitly explained. Montresor does allude to some wrongs committed against him by Fortunato. Is it possible to glean something from literary analysis?
The cask of Amontillado is the description of a murder by the murder himself, Montresor. As you have noticed, information about the motive for the crime is very scarce in this short story. There is no such thing as a third party in the story, who could express some kind of neutral point of view. Or more specifically, there is no external view except the reader's one. Some hypotheses can be made
- The Montresors used to be an established family, where honor was taken very seriously. A Montresor who's attacked must respond
Montresor: "The Montresors," I replied, "were a great and numerous family."
Fortunato: "I forget your arms."
M: "A huge human foot d'or, in a field azure; the foot crushes a serpent rampant whose fangs are imbedded in the heel."
F: "And the motto?"
M: "Nemo me impune lacessit." ¹
And as Montresor feels that he has been harmed by Fortunato...
The thousand injuries of Fortunato I had borne as I best could
... he then tries to take revenge.
- There is also a social difference between Montresor and Fortunato, that could have aggravated their mutual disdain. While Montresor has some noble roots, his name is declining. On the other hand, Fortunato is "rich, respected, admired, beloved" as Montresor says and the name "Fortunato" suggests. But Montresor also thinks that Fortunato do not deserve this success, and that he is an impostor in many areas
In painting and gemmary, Fortunato, like his countrymen, was a quack
All of Montresor's accusations against Fortunato are fuzzy, so he may also be mad.
Finally, an original theory was emitted by Cecil L. Moffitt. She noticed that Fortunato, despite being presented as a connoisseur of fine wine, claims some incorrect things about wine:
F: "Luchesi cannot tell Amontillado from Sherry."
while Amontillado is actually a type of Sherry. An oenophile (or more likely an insane oenophile) like Montresor might have some evil plans after that.
¹ "No one attacks me with impunity"