Most common-sense explanations of time quietly assume what they are supposed to explain.
We say time moves forward because clocks tick. But clocks only measuresomething, they do not explain why it has a direction.
We say time moves forward because the universe started in a special state. But that just pushes the mystery to the beginning and calls it a solution.
The arrow of time still looks like a narrative patch. A story we tell to make direction feel obvious.
The paper behind this post removes that patch and asks a more dangerous question:
what if direction is not built into the laws of nature at all, but produced by a constraint on which histories are even allowed to exist?
The definition that starts the fight
Instead of treating time as a background axis, the paper defines it operationally, by what it does.
Time is defined as the ordering that makes interconnected things most predictable together, given a minimal restriction on allowed futures.
Plain version:
when multiple things influence each other, there are many ways to order what happens. One ordering usually does a better job at making the present explain what comes next. That ordering earns the name “time”.
Not because a clock says so.
Because it works better.
This definition is provocative because it demotes time from a fundamental ingredient of reality to a performance criterion.
The heresy: the future as a filter
Here is where the paper becomes uncomfortable.
It introduces what it calls an admissibility set: a family of allowed endings. Not one fixed destiny. Not a goal. Not a target the system tries to reach. Just a weak filter saying: some endings count, others do not.
That filter changes everything.
If not every ending is allowed, then not every past can lead to an allowed ending. The space of possible histories collapses. Some histories survive the filter. Others are simply impossible.
In that setup, the arrow of time is not imposed by a mystical forward flow. It is selected.
The direction we experience is the direction along which histories remain compatible with the allowed endings.
This is the part that feels scandalous. It sounds like the future is doing work on the present.
The paper is explicit: this is not teleology. Systems are not “aiming” at anything. No intention is introduced. What breaks symmetry is conditioning, not purpose. Once you restrict which futures are admissible, asymmetry appears in the present as a matter of consistency.
Why this is not a poetic metaphor
This is not a metaphor dressed up as physics.
The microscopic laws can remain reversible. Nothing needs to “flow” forward at the fundamental level. Direction appears at the macroscopic level because admissibility reshapes which histories can exist without tearing the system’s correlations apart.
The arrow of time emerges as a selection effect on histories, evaluated through predictability across coupled observables.
That reframes the debate. Instead of “we started special, so now entropy increases,” the story becomes:
we are observing only those histories that remain compatible with a minimal late-time constraint.
A concrete analogy, without physics
Think about a story that must end in a certain kind of closure. Not one hookup, not one twist, but a narrow family of acceptable endings.
The moment you impose that constraint, the middle of the story becomes asymmetric. Some sequences of events still work. Others no longer make sense, because they cannot reach any acceptable ending without breaking coherence.
You can say “the ending shapes the story,” but the cleaner description is this:
the set of allowed endings filters the set of possible narratives, and the surviving narratives acquire direction.
The paper argues that physical histories can behave the same way, operationally and measurably.
One arrow, not many
The paper goes further and claims something quietly radical.
Instead of treating different arrows of time, thermodynamic, cosmological, as separate mysteries that need to be glued together, it treats them as expressions of the same mechanism.
When admissibility suppresses late-time macroscopic complexity, the arrows align.
When the admissibility constraint flattens, effective time symmetry returns.
Direction is not guaranteed. It is contingent.
The part that invites argument
The paper also draws a hard line around what people like to call “origins”.
If different admissibility choices do not produce distinguishable signatures in the present, then origin stories are not supported by evidence. They are narrative comfort, not operational claims.
This is the real provocation.
The drama of beginnings is replaced with a colder question:
what constraints on allowed endings actually leave measurable tracesnow?
Why this matters
If this framework is right, then time is not something we discover by looking backward toward a privileged start. It is something that emerges from how systems remain jointly intelligible under constraints.
That idea does not just challenge physics intuitions. It destabilizes how we talk about causality, prediction, explanation, and even narrative coherence.
One sentence to carry the controversy
The arrow of time is not a gift from clocks or a sacred first moment.
It is the scar left by a future filter on the set of histories we are allowed to inhabit.
About the author
Agustin V. Startari
**Affiliation:**UdelaR; Universidad de Palermo
Site: agustinvstartari.com
**SSRN Author Page:**papers.ssrn.com (Author ID 7639915)
ResearcherID: K-5792-2016
Linguistic theorist and researcher in historical studies. Author of Grammars of Power, Executable Power, and The Grammar of Objectivity.
Ethos
“I do not use artificial intelligence to write what I don’t know. I use it to challenge what I do. I write to reclaim the voice in an age of automated neutrality. My work is not outsourced. It is authored.”
If you want the full formal argument, the complete paper is available via my site and academic profiles.