Montresor tells his audience that he wants to exact revenge on Fortunato as a result of some unspecified "insult" to his person and "the thousand injuries" Fortunato has inflicted upon him. However, the story makes it seem as though it is both men's pride, in part, that prompts Montresor to murder. Montresor tells us that Fortunato "prided himself on his connoisseurship in wine," and he plays on Fortunato's extreme pride, subtly offering him the chance to flaunt his own expertise and laugh at Montresor's lesser skills, an opportunity he knows Fortunato cannot pass up. Fortunato even proudly insults Luchesi, the other town wine expert, insisting that he will accompany Montresor to his vaults. Montresor warns Fortunato that the vaults are terribly damp and not likely to be good for his lungs, but Fortunato's pride is so great that he will not hear of staying above ground. After one massive coughing fit, Montresor says,
Come. . . we will go back; your health is precious. You are rich, respected, admired, beloved; you are happy, as once I was. You are a man to be missed. For me it is no matter. We will go back; you will be ill, and I cannot be responsible. (my emphasis)
Montresor butters up Fortunato further, knowing that compliments which flatter his pride will hit their mark. However, he also says that Fortunato is happy, as Montresor once was, and this makes it sound as though Montresor's family is no longer as prominent. In other words, he is no longer as important socially, as Fortunato. He says that Fortunato would be missed, but he (Montresor) would not be missed.
In further support of this conclusion, Montresor comments in response to Fortunato's observation about the largeness of the vaults. He says, "'The Montresors. . . were a great and numerous family." He uses the past tense here, implying that the family is no longer important or large. Moreover, the Montresor family's motto translates to "You will not harm me with impunity"; or, in other words, you will not harm me and get away with it. Therefore, not only does Montresor have reason to exact revenge on Fortunato (as a result of the injuries and insults Fortunato has inflicted upon him), he also has his own injured pride, the result, perhaps, of his own family's fall from prominence (while Fortunato's star seems to be on the rise, something of which he is vastly proud).