Irony is a mode of discourse that presupposes a double audience. In this definition, one audience understands a surface-level message by what is said, and the other audience understands both the surface-level message, a deeper message, and the fact that the first audience only understands the surface-level message.

In the context of “Diary of a Madman,” Poprishchin serves as the first audience that is unaware of the double meaning, and the reader serves as the second audience that is aware of it and is aware of Poprishchin’s ignorance. Much of the content of Poprishchin’s letters is ironic because the reader understands, from Poprishchin’s narration of events, a different reality than he does and also recognizes that Poprishchin fails to understand this reality. This makes him a comically incompetent figure. He fails to see how ridiculous his pride seems as well as the fantasies he entertains, while the reader is well aware.

Digression in speech or rhetoric is when one strays off topic, and in the context of a story it is when a narrator provides details that are superfluous to the plot.