Symbolism
IKEA furniture store symbolizes the unnamed narrator's complacent, uninspired wish to do this.
What is "nest" at home where it's safe and comfortable, but where you don't grow as a person at all?
Tyler Durden's ingredients for the soap -- human fat from liposuction patients -- that he sells is reflective of this theme.
What is the theme of taking a consumer's own overconsumption and laziness and selling it back to them?
This moment when the unnamed narrator and Tyler Durden first meet on a plane and start a conversation is a metaphor for this.
What is the first time you look within yourself and listen to your inner voice?
The irony of Fight Club turning into Project Mayhem is arguably this.
What is that Project Mayhem is well-funded and overly confining, and exclusive, all things that were the exact opposite of the original intention of Fight Club?
Chronic insomnia is the unnamed narrator's first medical condition that starts him down his journey, but this condition symbolizes this.
What is that mainstream society and the conveniences of modern daily life don't give him anything meaningful to work hard for?
Tyler Durden is actually this.
What is the main character's alter-ego?
This literal location of Fight Club is a metaphor for how -- as with any of the really meaningful clubs we gravitate to, shine in, and truly feel like ourselves in -- being part of an underground scene is where the most innovation, passion, and creativity exists.
What is the literal basement of a pub/bar?
Bob Paulson's death is somewhat ironic for this reason.
The last thing the original Fight Club would have cared about were things like going on night-raids and sabotage operations. The original members just wanted a place where they could be themselves, not conform to societal standards or corporate standards, and therefore turn the volume down on everything they hate or are bored with in corporate life.
The moment where the unnamed narrator finally merges with Tyler Durden (after unsuccessfully trying to shoot and kill himself) is reflective of this deep theme.
What is the theme that in order to create, you have to destroy. This theme especially applies to destroying false versions of who you should be (spoon fed to you by images in corporate media advertisements, peer pressure, & mainstream societal pressure), so that you may find and become your true self?
When the unnamed narrator declares "I felt like destroying something beautiful" after beating up the blond Fight Club member until he is unrecognizable, this shocking scene is a metaphor for this idea.
What is you have to destroy some aspects of your former self if you want to become great or do great things?
The first "homework assignment" Tyler gives the Fight club members, to start a fight with a stranger and lose, is reflective of this theme?
What is the theme that learning to remain resilient and emotionally and spiritually unbroken while losing is often much more of a rich, valuable lesson than winning a conflict (where we often celebrate the win, but do no think about why or how we won. We might have just gotten lucky!).
When Tyler explains why there are oxygen masks on a plane, saying that inhaling oxygen makes passengers feel euphoria and keep calm, his lines of dialogue reflect this theme.
We're all mortal and will die: it's just that in modern life, we cling to so many material comforts and material luxuries that we have this false illusion of permanence and safety, when life is not necessarily safe. You can argue that it's not supposed to be. To feel truly alive is not necessarily about clinging to safety, but also about taking risks, and being bold and brave.