We've had a number of questions on the logic of the film via Twitter and other platforms.
Read on if you love massive spoilers.
Err, what is going on?
The logic of the film is actually pretty simple. When Mark starts thinking about a bit of his story elements of that story appear in real life. If he just thinks about that bit of the story the things eventually disappear - though they leave traces. If he writes about them then they remain fixed.
Once things have happened Mark can’t “unhappen” them. They have entered the fabric of reality.
MARK: “It’s always been when I’m making the story in some way. In my head.”
If he just needs to think of something for it to happen in real life, how come it doesn’t happen to him all the time?
The logic of the film is that the things only happen when his mind is being creative specifically in the context of this particular story that he is writing about the navvies / railway. This is why imagining the doctor under the bridge does not work at the end.
Alright, but this is pretty fanciful, how did it come about at all that he could do this?
We never find out and nor do the characters themselves. Lots of films don’t explain their setup mechanisms, eg, the repeated days in Groundhog Day, the military dream infiltration technology in Inception.
The philosophical subtext of the film is that actually we CAN manipulate reality with our ideas and already do so all the time. We imagine things and they happen - skyscrapers and spaceships appear which were not there before. OK we use technology to build them - but we always imagine them first.
Creative thinking has always been the thing that allows people to solve the problems that face them.
How come it happens with some bits of the story and not with other bits, IE how come the WHOLE story he is writing doesn’t materialise in real life.
We never find out. But it always happens when a part of the story is particularly occupying him, just as when people become particularly occupied with a problem they create a solution to it, and therefore change reality only in relation to that problem.
What is going on with Harry and Edna? Is Mark’s condition hereditary?
We don’t know. All we know for certain is that Harry left Mark the house when he died after he had no children of his own. There is no suggestion that the house has a curse on it or is haunted, we only know that the events start happening to Mark and Sarah after they move in.
It might be the house, it might be the railway, it might be another trigger entirely. There is a brief hint that Harry may have had similar experiences to Mark, though it is never explored.
EDNA: “Funnily enough Harry had also started to research Mac’s story with a view to writing about him but gave up shortly before he died - he never told me why.”
What is going on when Mark is chasing himself and blabbering about old rules and new rules at the end? Mark realises at the end that he is as good as telling a story in real life - he thinks of events and they happen. But if he’s already written something he knows he can’t change the events in real life that result from them. And he wrote about the smallpox - so it’s set.
MARK: “I took a note from the voicemail.” SARAH: “Does that count?”
MARK: “I don’t know. I mean it occured to me I could use it in the story for a split second before I ...”
But then he realises there is a way to avoid this. If he makes the events of the old story fit with a new narrative that bookends them, then the old events - specifically the smallpox incident - can be fitted with a new ending.
So he creates the idea that he is an author that has created the story of a suicidal writer (essentially the story as it had been in real life up to that point - remember he tries to commit suicide at the start of the film) as a warning to himself on how self-involved and solipsistic writing can become, so that the author can finally give up the hobby for ever.
This frees him from the previous ending because it’s events still happen, just to a version of himself that he has created, rather than to his real self.
As we know from the original rules he can create stories that happen in real life, which is really all he has done here, he’s just added another level.
Hold on - how can he be in both stories at once but not be able to rewrite the original story. Isn’t that two versions of the same thing?
Mark couldn’t rewrite the original story because that would have meant changing events that had already happened and that were in the past. That is against the rules of that story. But if he subsumes that story into a wider one, then he can make it so that those same events still happen, but in a different context that frees him to change the ending, IE to a version of himself he has just created rather than to himself.
He can just create a version of himself just like that?
He thinks of things and then they happen in real life. There’s no reason that this wouldn’t apply to there being two of him. The only complexity is once he has created two of him which one is doing the thinking and which one is being manipulated as part of the story. To solve this in the new story he creates a new rule that says that the new him is the real him.
This does not contradict anything in the original story because there was only one of him so no historical precedent for which of two versions of him would end up being the real one.
So let’s backtrack to the whole outlook of the film. I’m still confused - is it all in his head or not? What about the folie a deux?
The folie a deux is one early theory as to what is going on, but their testing disproves it. The real- life events happen even when Mark is on the antipsychotics and they have a number of objective confirmations from lab-reports etc.
What IS actually going on then?
One of the points of the film is that we can never really know the truth about the world outside of us. All we can ever do is create better and better working theories as to the operations of that world and how we can interact with it.
A number of explanations as to the nature of reality have been created and subsumed in this way throughout history. Newton’s laws of physics were subsumed by Einstein’s theory of relativity, which was subsumed by string theory, which will be subsumed by something else.
SARAH: “Nobody’s ever right. We just...edge closer.”
Humankind achieves this progression of ideas by the creation, and then the testing of, theories, usually to solve problems, just as Sarah and Mark create a theory and then test it to solve their problems.
So just like us, Mark and Sarah only know a slice of the ultimate truth at the end of the film, and it is the truth that their theories and experimentations have brought them to at that point: that for whatever reason Mark really can create stories with his head which affect material reality as they, and third part corroborators, perceive it.
Maybe further down the line, they, like us, will eventually come up with a theory that explains more completely what is going on and why. Maybe they won’t.
But one thing is certain: they only have a chance of doing so if they remain determined, open to new ideas, willing to communicate, and more than anything only if they truly believe that it is possible to create such a theory in the first place.