Even though Patrick Bateman is a self absorbed loser, he wasn't wrong when he said "There is an idea of a Patrick Bateman"
Sure, he meant it in a "I'm a psychopath and nobody knows it" way, but when observing the people around him, it isn't wrong to say that it's true.
Names are a loose concept to Wall Street men. Everyone pretty much shares the same mass illusion of what status a specific name carries. They don't know who that person actually is and just assume that they're talking about the same person.
This was inspired by a post I saw that said something along the lines of "My theory is that Patrick Bateman is actually Marcus Halberstram and that 'Marcus' is actually 'Patrick'", but I heavily disagree.
First of all, we don't even know if the person who Patrick calls Marcus IS Marcus. Patrick himself doesn't have a shared name amongst his co-workers (a random co-worker in the hall (the sigma walking scene if that jogs anyone's memory) calls him "Hamilton", Paul Allen calls him "Marcus Halberstram", his lawyer, Harold Carnes, calls him "Davis"). How we do know that Patrick is Patrick is from the interactions with Jean and detective Donald Kimball, and overall personal relationships he had.
Detective Kimball addresses him by Patrick Bateman multiple times. Most people would agree that Kimball was suspicious of Patrick (I personally believe that Willem Dafoe in general looks like he knows your deepest secrets), so wouldn't his name be something he'd ask about?
Jean, as his secretary, handles his work and probably legal issues, so she definitely knows his legal name.
Legally changing his name doesn't count cause then he IS Patrick Bateman. And if he did so, he'd done it long before meeting any of his friends. Imagine changing your name when you're friends with a group of bigots... Do you really think that they'd let that down? Ever?
Plus, in the story we run into people from his past, some from his college years (in the book), and they all call him Patrick.
And since we are talking about legal issues, Harold Carnes is NOT somebody I'd trust with anything. He probably works for more than half the company, most likely bribes the judges and other notorious "lawyer" stuff.
You can argue "Well, he was trying to make it into a joke so Patrick wouldn't get into trouble", but not directly telling a mentally unwell person (an understatement of the century right here) who famously can't read body language or pick up on social cues to follow a storyline you made up will lead to more trouble in the long-run.
And anyway, I don't think he's that smart to come up with that in the first place.
Or maybe he's lazy enough to not care about the consequences.
And to add to this, Paul Allen calls Craig McDermott "Baxter" in the famous card scene. Unless that is an 80s slang for something (which I doubt since in the script it's written with a capital letter, indicating a name, more likely a surname), the "nobody knows who anybody is" theory just proves to be correct again... Well, it isn't really a theory, but still.
If anyone disagrees or has anything to add, please do! I love discussing my favorite media!!!