In Edgar Allan Poe’s short story The Cask of Amontillado, Fortunato, as described by the man who will murder him, Montresor, is no fool; he is “a man to be respected and even feared.” As such, Montresor has had to carefully plan his assault on the man who has cast a “thousand injuries” upon him, waiting for the moment when his intended victim would be at his most vulnerable. Knowing Fortunato well, Montresor has chosen the annual carnival in this presumably fictitious Italian city or village, when much of the local populace can be expected to be inebriated, which proves the case with Fortunato:
“. . .the supreme madness of the carnival season, that I encountered my friend. He accosted me with excessive warmth, for he had been drinking much. The man wore motley. He had on a tightfitting parti-striped dress, and his head was surmounted by the conical cap and bells.”
The significance of Fortunato’s attire lies in the impression of the fool he conveys dressed as he is and stumbling about from excessive drink. Montresor has planned well; this man to be respected and even feared has his guard down and is incapable of rational thought or resistance because of his drunken state. The costume Fortunato wears symbolizes the diminished mental state – in effect, he has become ‘the idiot’ -- to which he has descended.
When people choose a costume to wear at a party, it is natural for them to choose one that represents how they think of themselves or what they would like to be. This is still true today, although most people only wear costumes on Halloween. Fortunato is drunk when Montresor encounters him, but he wasn't drunk when he chose his costume. In those days he would have had to have the costume tailor-made, so he would have made his choice some time before the carnival. The fact that he chose a court jester's costume shows that he thinks of himself as a funny fellow, a jester, a man who likes to play practical jokes. No doubt he is enjoying himself by blowing a tin horn in people's ears and throwing confetti in their faces. This is one of the characteristics Poe wants to give Fortunato. It suggests that many of the "thousand injuries" he has inflicted on Montresor, though cruel, were regarded by Fortunato as "jests." What Montresor does to him in revenge might be considered a practical joke. Fortunato himself tries to laugh it off as a jest in order to give Montresor a chance to change his mind and an excuse for having lured him into this trap. Here are Fortunato's words.
“Ha! ha! ha!—he! he! he!—a very good joke, indeed—an excellent jest. We will have many a rich laugh about it at the palazzo—he! he! he!—over our wine—he! he! he!”
“The Amontillado!” I said.
“He! he! he!—he! he! he!—yes, the Amontillado. But is it not getting late? Will not they be awaiting us at the palazzo, the Lady Fortunato and the rest? Let us be gone.”
Although the author doesn't say as much in words, there is a strong suggestion that the two men earn their livings through buying and selling luxury items.
In painting and gemmary, Fortunato, like his countrymen, was a quack, but in the matter of old wines he was sincere. In this respect I did not differ from him materially;—I was skilful in the Italian vintages myself, and bought largely whenever I could.
Most of the injuries Montresor has suffered have probably been in business relations. Sometimes they are competitors and sometimes they may be partners--but Fortunato always comes out ahead and laughs it off as an excellent jest. He is not a fun-loving man but a cruel man who gets fun out of hurting others through cunning trickery. Montresor continues his pretense of friendship because Fortunato is rich while he himself is poor. He may need to borrow money. He may collect a finder's fee when a particular object, such as a Renaissance painting, is too rich for his blood. Or he may go into ad hoc partnerships with Fortunato, in which case his "good friend" might demand a sixty-forty split of the profits. Venice was full of old aristocratic families who were gradually selling off paintings, statues, jewelry (gemmary), antiques, wall hangings, and other valuables in order to stay alive.
Neither of these men is interested in buying a "pipe" of Amontillado for personal consumption. A pipe contains 126 gallons. What interests Fortunato, as it supposedly does Montresor, is that he bought his cask as a "bargain" price. He supposedly intends to make a profit, but he supposedly needs to have the wine authenticated before he buys more. Montresor knows that Fortunato will immediately be thinking of one of his clever "jests." He will taste Montresor's (nonexistent) wine and say it is only ordinary sherry. Then he will find the Spanish ship that must have just arrived from Barcelona and buy up the entire cargo. When Montresor supposedly finds out that he has been tricked, Fortunato will laugh off this one-thousand-and-first injury as "a clever jest." But this time the joke is on Fortunato.
(Please refer to my extended explication of "The Cask of Amontillado" by clicking the eNotes reference link below.)