Some people speak of themselves in the third person. It can be annoying. But if people start seeing themselves in the third person—well, that's just crazy.
Not only is our narrator seeing things that doesn't exist—having chronic insomnia will do that to a guy—the thing he's most seeing is a person, and that person is a twisted version of his own personality. To crank the madness dial up to eleven, he starts listening to and following this figment of his imagination as well…and inspiring others to do the same. At least he's making sure he's not the only crazy one in the group.
Questions About Madness
Is our narrator/Tyler insane? Or is he the only sane one in an insane world?
Why do people follow the narrator/Tyler even though they all pretty much know he's cuckoo?
Will our narrator be less crazy after the end of the movie, and seemingly eliminate the Tyler side of his personality?
Chew on This
You have to be kind of crazy to join fight club, so it's not a stretch for these men to pretend like our narrator/Tyler is normal.
Marla is bored with life, so she's attracted to our narrator/Tyler because he's insane. Insanity is interesting.