“What is relational is real, and what is real is relational”: an ontological assessment of Relational Quantum Mechanics

For over a century, physicists have grappled with a strange truth about the universe: the world does not behave the way our daily experience suggests it should. In the familiar realm of tables, chairs, and planets, objects exist with definite properties whether anyone is looking at them or not. A tree falling in a forest makes a sound regardless of a listener. But in the microscopic realm of atoms and electrons, this common sense breaks down. The behavior of these tiny particles seems to depend entirely on how they are measured or observed. This has led to a long-standing debate about what is actually real. Does the universe consist of solid, independent things that happen to interact, or is reality itself made of something more fluid? One prominent view, known as Relational Quantum Mechanics, proposes that the latter is true. It suggests that properties like position or speed do not belong to an object in isolation; they only exist when that object interacts with something else. This idea challenges the deep-seated belief that there is a single, absolute description of the universe that exists independently of any observer.

A new paper by Juan Vila, a researcher at the National University of Tres de Febrero, takes a close look at this relational view to see if it can hold up as a serious description of reality. The paper does not propose a new experiment or a new equation. Instead, it acts as a philosophical map, tracing the logical consequences of the relational idea to see where it leads and where it might stumble. The author begins by reconstructing the core argument of the theory's founder, Carlo Rovelli. The argument starts with a simple but radical observation: in quantum mechanics, two different observers can describe the exact same sequence of events in completely different ways, and both descriptions can be correct. One observer might see a particle having landed in a specific spot, while a second observer, looking at the first observer and the particle together, sees them both in a fuzzy, undefined state. The theory resolves this by saying there is no single, "God's-eye view" of the universe. Instead, reality is a collection of perspectives. A system is only in a specific state relative to another system it is interacting with.

The paper then tackles a major criticism often leveled at this view: that if reality depends on who is looking, then nothing is truly real, and we are left with a confusing mess where anything goes. Vila argues that this criticism misunderstands the theory. The relational view does not say that reality is a figment of human imagination or that it changes based on our beliefs. It says that reality is made of physical interactions. Just as a thermometer has a temperature only because it is in contact with the air or water it is measuring, a particle has a state only because it is in contact with another system. The author defends the idea that this is still a form of realism, just a weaker one than the traditional kind. It accepts that the world exists outside of our minds, but it rejects the idea that the world is made of permanent, unchanging "things" that carry their own private properties.

However, the paper finds that even this relational view has not fully escaped the old habit of thinking in terms of solid objects. The author examines three different ways philosophers have tried to explain what the basic building blocks of this relational world are. One group suggests the building blocks are "dispositions," or hidden potentials waiting to happen. Another group suggests the building blocks are "structures" that remain the same even as the view changes. A third group suggests the building blocks are "transcendental conditions," or rules about how we can think about the world. Vila argues that all three of these approaches fail because they are still trying to find a solid, unchanging foundation underneath the relations. They are trying to put a floor under a house that is built entirely of bridges. They are looking for a "thing" that exists before the interaction, which contradicts the core idea of the theory.

To solve this, the paper proposes a fresh way to think about what a "system" actually is. Instead of imagining a particle as a tiny, solid ball that exists on its own, the author suggests we view it as a "pattern." This idea draws on the work of philosopher Daniel Dennett. A pattern is not a physical object in the same way a rock is; it is a regularity, a repetition, or an order that appears in a stream of events. Think of a series of dots on a screen. If the dots are arranged in a perfect, repeating grid, we see a pattern. If the dots are scattered randomly with no order, we see noise. The paper argues that a physical system, like an electron, is real only if it forms a recognizable, compressible pattern of events. It is the order itself that is real, not the underlying "thing" that supposedly holds the order. This allows the theory to remain radical: there are no permanent substances. There are only events, and when those events repeat in a specific, law-like way, they create the illusion of a stable object.

The paper concludes that this shift in perspective is necessary to make sense of the quantum world without falling back into old habits. It suggests that the universe is not a collection of actors on a stage, but a continuous flow of interactions. The "things" we see, from atoms to cats, are just stable patterns that emerge from this flow. When we look at the world, we are not seeing independent objects; we are seeing the regularities that arise when different parts of the universe interact. The author acknowledges that this is a difficult idea to accept because our brains are wired to see solid things. We are used to thinking of the world as made of nouns—objects, particles, people—rather than verbs, interactions, and events. But the paper insists that if we want to understand the universe as quantum mechanics describes it, we must be willing to let go of the idea of permanent things and embrace a world where reality is fundamentally relational. The solidity of the world is not a given; it is a pattern that emerges from the constant, dynamic dance of physical interactions.