Probabilistic presentism
Probabilistic presentism has an ambition: to unify physics within a single framework, from time and quantum physics to gravity. Its starting point: only the present exists, carrying traces of the past and possible futures.
The future is open.
Reality takes shape in the present.
The challenge of unification
How can we describe the same Universe within a common physical framework? Generations of researchers have grappled with this question.
Attempts at unification often lead to highly complex constructions. My intuition is that this difficulty may point to a conceptual framework that needs rethinking: we may be trying to fit a square peg into a round hole.
Probabilistic presentism explores a different starting point, with the ambition of finding a simpler, more coherent and more elegant description of reality.
Alexandre Leroy · The starting intuition
General relativity describes gravity and the geometry of spacetime. Quantum physics describes, among other things, particles and their interactions. Each achieves remarkable success in its own domain.
But bringing them together remains one of the great challenges of physics. Gravity is missing from the Standard Model of particle physics. Despite decades of work and many approaches, no framework bringing gravity and quantum physics together has yet received decisive experimental confirmation.
Probabilistic presentism is part of this quest: exploring a path towards unification through the present, possibilities and traces, while preserving the established achievements of the major theories.
For context on this challenge: the Standard Model explained by CERN · a century of research into quantum gravity.
A small scene. A big idea.
Imagine: you are in a room. A glass sits at the edge of a table. Nothing has happened yet.
What will happen? Follow the scene to discover probabilistic presentism, without equations.
Possibilities
The glass could stay upright, fall without breaking or shatter. These outcomes do not necessarily have the same probability: in other words, the same chance of happening.
Its position, a movement of the table or an approaching hand changes the situation. Some outcomes become more likely, others less so.
The “field of possibilities” is the set of possible continuations in this situation.
Actualization
It is no longer a possibility: it is what has just happened. The model calls this transition to fact “actualization”.
For this event, the realized outcome is now at 1 — or 100% — and the other alternatives at 0. They are not what happened.
Before: several possible outcomes. Now: a fact.
A less likely outcome can also occur. “More likely” does not mean “already decided”.
The consequences
The shards scatter. The sound travels. Someone hears it and turns around. This does not all happen everywhere at the same instant: the effects gradually reach what surrounds the glass.
The pieces remain on the floor. They are traces of the event: something from the past still exists in the present situation.
What happened is now transforming the conditions for what follows.
The new possibilities
The person can pick up the pieces, warn someone or walk around the shards. These possibilities make sense in the new situation.
What happens next will, in turn, leave traces and change the probabilities of subsequent events. The cycle continues.
Facts transform possibilities. Possibilities give rise to new facts.
You have just followed the heart of the idea: what happens changes what can happen next.
Let us step back: see how this movement renews itself, then what it changes in a life.
The overall process
In probabilistic presentism, what we call “the future” is a set of possibilities carried by the present: the field of potentiality.
Each event that becomes real changes what can happen next. As its consequences spread, some possibilities grow stronger, others fade, and new ones emerge.
The future is not a script waiting to unfold. It is reshaped by what happens.
The presentActualization threshold
On the line of the present, a possibility becomes a fact. To the right, its consequences spread.
Several events are possible, with different probabilities.
The situation evolves. Some possibilities strengthen, others fade.
The transition point between what can happen and what becomes a fact.
One outcome is realized: 1 for the actualized fact, 0 for its alternatives.
They gradually reach its surroundings and change the possibilities ahead.
The consequences reconfigure subsequent probabilities. The cycle continues.
From possibilities to an actual fact
Imagine what comes next as still blurred. Several futures are possible; none has happened yet.
As you move down this drawing, possibilities become more defined and condense. At the actualization threshold, a possibility becomes a real event.
Its consequences then spread and transform the possibilities ahead. The movement continues.
Possibilities take shape. An event becomes real.
Feedback reshapes the whole field of possibilities: from the most diffuse to those close to actualization, as consequences spread.
What about in a person's life?
Making a decision is also an event. Its consequences unfold over time.
Consider someone living with alcohol dependence. Their habits and situation favour recurring difficulties, for them and for those around them. One day, they make a firm decision to begin working towards stopping.
Their commitment is now part of the present. Their intentions and the actions they consider are reorganized: asking for help, talking to someone close to them, accepting support.
In this interpretation, the landscape of possibilities begins to reconfigure, even before all the effects are visible.
The person talks about it, seeks support and takes action. Those around them respond to what they learn and observe. Each step creates a new situation.
The decision opens up a path; it does not guarantee the outcome on its own. Change continues through actions, concrete circumstances and support.
What changes immediately within a person can gradually transform what becomes possible around them.
This example illustrates a decision and its effects, not a treatment method. Not all events in reality require a conscious decision.
Another way of looking at the world
It happened. What acts today are the traces and transformations it has left in the present.
This is where possibilities become facts and their consequences change the situation.
In the model, it is not a story that has already happened. Its possibilities evolve with events.
Making sense of it
It is a way of expressing the chance that an event will happen. 0 means impossible, 1 means certain; we can also write 0% and 100%. In between, several outcomes remain possible. The examples on this site consider mutually exclusive alternatives for the same event.
The model proposes that the openness of some possibilities belongs to reality itself. It does not simply say that we lack information about a story that is already fixed.
No. A detector can record a result before a human looks at it. Actualization does not require a conscious decision.
This reading path explains probabilistic presentism. Its arguments, formulations and scientific status are presented alongside the texts.
The texts and the model's status →Read at your own pace
Would you rather continue here? The “Understand” guide revisits these ideas and connects them to time, matter, gravity and quantum physics.
Continue with the illustrated guide →
Find the detailed reasoning, illustrations and references in the essay. The preprints develop the physical proposals.
The author and publicationsA world that is not already written
Read the essay · PDF in FrenchIn French · Version 1.1 · Alexandre Leroy
As of 6 September 2026
The present, possible futures and actualization are also the subjects of other research. Explore the authors, their work and links to the original texts.
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