Who is the narrator, can she or he read minds, and, more importantly, can we trust her or him?
First Person (Central Narrator)
Poprishchin is not just at the steering wheel of this wild bus ride through insanity, he's also the one holding the mic and telling us all about what's going on out there. Of course, when you see a madman in that seat with the mic in his hand, you have to ask yourself: hmm, how reliable is he? Well, he does think that dogs talk and write, and he believes he's the King of Spain, but he still continues to describe as best he can what he thinks is happening, right? So we can give him some credit here in the reliability department.
The only time we're not fully inside his head is when he quotes from what other people have told him (he's disorganized, socially inept, etc.). The stuff he quotes seems to mesh with the kind of idea we get about him from reading his diary, so we can probably believe him when it gets to these quotes. Another point at which it seems like we're not inside Poprishchin's head is when he is quoting directly from the dogs' letters. But since we suspect these letters don't really exist, we're probably more inside his delusional head than ever.
So even though the narrator Gogol gives us is mad, that doesn't mean he is out to pull any tricks on us in his diary. He's too naïve to be a schemer. He just wants to note everything down as he thinks it happens, and we get an up-close-and-personal look at his loosening hold on reality. We're left to figure out what is really going on by reading his descriptions of the reactions of the other characters. He doesn't see that his behavior is alarming to others, but we sure do.
Poprishchin starts his diary by telling us about an "extraordinary adventure." If you've ever kept a diary, you know that you probably write more when confusing or troubling or just really interesting stuff is happening in your own life. Maybe it's a way to make sense of things or just to keep track of all the changes during a challenging or scary time. Great example: Anne Frank.