Why not all versions of physics can work
The key idea of the paper is that once you take distinguishability seriously, you don’t get to build physics however you like. Certain features stop being optional — they become necessary.
For example, if a difference can simply be undone at any moment, then it was never really a fact to begin with. It was just temporary. So for reality to contain actual, stable facts, there must be irreversibility — once something happens, it truly happens and can’t just be erased by the rules of the system.
Then there’s structure. Facts can’t just exist in isolation — physics is about how things relate to each other. That means facts must be able to combine and form more complex facts. If they can’t, you don’t get a universe with relationships, laws, or patterns — you just get disconnected moments. So the system must allow for compositional structure, where pieces of reality fit together consistently.
And it turns out, this puts surprisingly tight limits on how reality can be built. Below a certain level of structural complexity, things either fall apart or collapse into something trivial. The framework shows that there is a minimum architecture needed for reality to work in this way — and that minimum isn’t arbitrary.
One underlying structure, not many
There’s one more important piece. If physics is describing reality, it can’t be built out of multiple unrelated “layers” that don’t connect at a fundamental level. There has to be a single underlying structure that everything comes from — a common source that all observable quantities relate back to.
Otherwise, you don’t really have one reality — you have several overlapping ones with no clear way to reconcile them.
So the conclusion is surprisingly strong:
If you want a universe where facts exist, persist, and relate to each other in a meaningful way, then the underlying structure of that universe is heavily constrained.
What this means
This doesn’t prove that one specific theory is the final answer. But it does something just as important:
It shows that not all theories are equally possible.
Once you demand:
- real, stable facts
- meaningful relationships between them
- and a consistent underlying description
…the space of viable physics shrinks dramatically.
The VERSF framework is presented as one realisation of that tightly constrained space — not as an arbitrary idea, but as something that emerges when you follow those basic requirements all the way down.
The big shift
The deeper message of the paper is this:
Physics may not just be about describing reality — it may be about discovering the only kinds of structures that reality can have at all.
And if that’s true, then instead of endlessly searching through possible theories, we may be able to rule most of them out from the start.
That’s a very different way of thinking about how physics works—and it’s what this paper is trying to make precise.