We tend to think of entropy as a flexible idea—something physicists can define in different ways depending on the situation. But what if that freedom isn’t real? What if, once you take seriously what it means to record information in the physical world, there is only one way entropy can be defined?
This new paper explores that question from first principles. It starts with something very simple: what does it actually mean for something to be a record? A record has to persist. It has to be readable. And it has to represent a real, measurable difference. From those basic ideas alone, the paper shows that entropy can’t be defined arbitrarily—it has to match exactly what a theory can physically distinguish. You can’t count differences that no experiment could ever detect, and you can’t ignore differences that experiments clearly reveal.
Within the VERSF framework, this leads to a striking result. VERSF describes reality as emerging from a deeper “void” structure, where distinctions become real through irreversible events. That structure naturally groups states into classes based on what is physically meaningful. The paper proves that these classes line up perfectly with what we can observe in practice. And once that happens, the entropy is no longer a choice—it is uniquely fixed.
The outcome is simple but powerful: a key parameter in the theory, called η, is forced to equal one. There is no tuning, no ambiguity, and no alternative that works. More broadly, the work suggests something deeper: in any physical theory, the way we count “microstates” isn’t arbitrary. It is constrained by what reality itself allows us to distinguish.