We began with a question about quantum mechanics.
How can a physical system described by a superposition of possible states yield a particular outcome? Why does the mathematical representation of quantum possibilities appear so different from the actuality of the world we encounter?
As we followed the question from measurement to cosmology, another difficulty emerged. The mathematical representation of potential states was increasingly treated as though it provided an account of multiple actual physical conditions. The problem of measurement consequently became a problem of explaining how those conditions become one.
But perhaps the difficulty arises partly from the way we understand actuality itself.
What if the physical world does not consist of a collection of possibilities waiting to be actualised by measurement? What if actuality is something we should understand through the relations and interactions constituting the physical world?
The actuality of relations
We ordinarily encounter the world as a world of actual things.
Particles interact. Atoms form molecules. Stars develop. Galaxies emerge and persist. These entities exist through physical relations, and their behaviour depends upon the interactions in which they participate.
Their actuality is not simply a matter of their being observed.
A galaxy does not become an actual astronomical structure because an observer identifies its location. Its physical organisation and relations are part of what makes it the entity it is.
This suggests a different starting point for understanding physical actuality.
Rather than treating actuality as something that must be added to a mathematical representation of possibilities, we can begin with the physical relations and interactions through which entities exist and behave.
The world is not waiting for an observer to convert its possibilities into reality.
It is already an actual physical world.
Potentiality and actuality
The distinction between potentiality and actuality has been central to our investigation.
A physical system may possess potential outcomes that are represented mathematically. Those potentialities are physically significant. They are not necessarily expressions of ignorance, and quantum interference demonstrates that the relationships between them can have observable consequences.
But potentiality is not another form of actuality.
The representation of several possible outcomes does not establish that all those outcomes exist as actual physical conditions. Nor does the mathematical representation of alternative configurations establish that the corresponding entities exist simultaneously.
Potentiality concerns what may become actual through physical processes and relations.
Actuality concerns what exists and occurs within those relations.
The distinction does not require us to deny the physical significance of quantum superpositions. It requires us to examine what the mathematical representation of a superposition establishes about the physical system being represented.
The question is not whether quantum potentiality is real.
It is whether we have adequately distinguished its physical significance from the actuality of the outcomes and structures we investigate.
Measurement without an observing universe
The measurement problem becomes particularly interesting when we consider the role of the observer.
In conventional formulations, measurement appears to introduce a special difficulty. A quantum system evolves according to the mathematical formalism, yet measurement yields a particular outcome. The relationship between quantum evolution and definite outcomes consequently becomes a central problem.
But the physical world does not depend upon human observation for its existence.
Measurement is itself a physical process. It involves interactions between systems, the development of correlations and the production of records. An observer participates in this process, but the existence of physical actuality need not depend upon the observer's awareness.
From a relational perspective, this distinction matters.
The actuality of a physical entity is constituted through its relations and interactions, not through the act of someone looking at it.
This does not tell us exactly how quantum measurement produces particular outcomes. The mathematical and physical questions remain. But it removes the assumption that actuality must somehow be conferred upon the world by an observer.
We can investigate measurement as a physical process without treating observation as the source of existence.
The organisation of actuality
The distinction becomes even more important when we consider the different levels of physical organisation.
A galaxy is not simply a very large particle. It is an organised physical system whose actuality involves the relations among its constituents and its interactions with other structures.
Its formation involves a history of physical processes. Its persistence involves the continuing organisation of its components. Its location and behaviour are part of its relations with the wider universe.
Quantum physics applies to the matter and fields involved in these processes. But the actuality of a galaxy cannot be understood simply by enlarging a mathematical description of an elementary particle.
The physical organisation of the galaxy matters.
This does not mean that different physical levels exist independently of one another. The development of macroscopic structures depends upon the physical processes occurring at smaller scales.
But the continuity of those processes does not make every ontological question identical across the different levels.
We need to understand how physical organisation develops, how relations are established and maintained, and how the actuality of particular structures emerges through their histories.
The universe is not merely a collection of quantum descriptions.
It is an organised physical world.
What mathematics tells us
None of this diminishes the achievements of mathematical physics.
Quantum mechanics provides extraordinarily powerful resources for describing physical systems and predicting the outcomes of interactions. Quantum field theory and cosmology extend those resources into domains that would otherwise remain inaccessible to investigation.
The question is not whether mathematical descriptions are connected to physical reality.
They plainly are.
The question is whether the mathematical representation of physical possibilities should be treated as a complete account of physical actuality.
A mathematical description can represent potential outcomes, relationships between alternatives and the conditions under which particular phenomena become observable.
But the physical world is not identical to the mathematical representation through which we investigate it.
The success of the representation does not automatically establish the ontological interpretation attached to it.
This distinction is especially important when mathematical descriptions developed for one physical context are extended to another.
The applicability of quantum theory to cosmological phenomena does not mean that the actuality of galaxies can be understood simply by treating them as enlarged quantum particles.
We need to investigate the physical organisation of the universe, not merely extrapolate the mathematical representation of its constituents.
The actuality of the universe
Perhaps the difficulty that motivated our investigation can now be reconsidered.
We began by asking why quantum possibilities do not appear as multiple actualities in the macroscopic world.
But the question may have assumed too much.
The mathematical representation of potential outcomes does not establish that those outcomes are all actual physical conditions. The suppression of interference does not, by itself, explain the actuality of a particular outcome. And the applicability of quantum theory to the early universe does not establish that galaxies should be understood as multiple actual astronomical structures.
These distinctions do not resolve every problem in quantum mechanics.
They do, however, suggest that the relationship between potentiality and actuality deserves more careful attention than it sometimes receives.
A relational ontology offers a different starting point.
Actuality is not something that must be added to a mathematical representation of possibilities. It is the physical world constituted through relations and interactions.
Potentiality is not a collection of alternative actualities. It is a physically significant aspect of what may become actual.
Measurement is not the act through which an observer creates existence. It is a physical process occurring within an already actual world.
And the universe is not simply a mathematical collection of possible configurations. It is an organised physical reality, developing through relations and interactions across different scales.
Perhaps, then, the question is not how reality became actual.
Perhaps the question is why we came to think that actuality needed to be explained as something separate from the physical relations through which the world exists.
That is where our investigation leaves us.
Not with a solution to quantum mechanics, but with a different understanding of the problem we set out to investigate.
The universe is actual.
And perhaps we should begin there.