This question already has an answer here:
In the movie Fight Club, the narrator (Edword norton) makes an illusionary personality, Tyler durden (Brad Pitt), around himself and the movie goes on. At the end of the movie, the narrator (Edword norton) says "Tyler, my eyes are open" and he puts the gun in his mouth and shoots himself, and in result of that Tyler Durden dies but he lives.
When he said that "Tyler, my eyes are open", he wanted to make sure that he wasn't dreaming or he wasn't insomniac at that time and shoots himself for real. How is it physically possible that he got to live after that but his illusion magically dies?