In the previous essay, we asked a deceptively simple question:
What does a particle do?
We discovered that the question becomes more interesting when we stop looking for a purpose and start looking for a capacity.
An electron does not exist for chemistry. But its properties participate in the physical arrangements that make chemistry possible. A photon does not exist for vision. But electromagnetic radiation can participate in arrangements that eventually allow organisms to detect and respond to their environments.
There is therefore a distinction worth making at the outset.
When we speak of the "function" of an electron or photon in this series, we mean simply what it does, or what role its behaviour plays. We are not attributing intention, purpose or foresight to particles.
That clarification matters because the word function can easily mislead us.
But once we have removed the teleological worry, another question appears.
If a particle has properties, and those properties give it capacities, where do possibilities enter the story?
A property is not yet a possibility
Suppose we say that an electron has negative electric charge.
That is a statement about the electron.
But it is not yet a statement about what the electron can make possible.
To get there, we have to consider what happens when the electron enters into relations with other entities.
Its charge makes it responsive to electromagnetic fields and allows it to participate in electromagnetic interactions. Its quantum properties constrain the states available to it. Those constraints and interactions contribute to the structures of atoms.
And atoms can participate in chemical interactions.
The important point is that the electron's property does not sit inside it like a tool waiting to be taken out and used.
A property becomes consequential through relations.
This suggests that there is a hidden step between property and possibility:
property → capacity → relation → possibility
The capacity is not something additional to the property in the way that a new physical component might be added. Rather, it is the property considered in terms of what it permits or constrains within an environment.
Electric charge is a property.
Interaction through the electromagnetic field is a capacity associated with that property.
And once that capacity participates in an appropriate organisation, new possibilities arise.
This may sound like nothing more than a change of vocabulary.
Perhaps it is.
But sometimes changing the question changes what becomes visible.
The isolated particle is a conceptual convenience
Physics often begins by isolating things.
We ask about an electron.
We calculate what happens to a photon.
We determine the properties of a quark.
This is enormously useful. Without abstraction and isolation, much of physics would be impossible to formulate.
But the success of the abstraction can tempt us into forgetting that the physical world itself is not composed of isolated textbook examples.
Particles interact.
Fields interact.
Particles and fields interact.
And out of these interactions arise structures.
An electron by itself is one thing.
An electron participating in an atom is something else—not because the electron has changed species, but because the possibilities available within the larger system have changed.
The same electron can participate in enormously different physical organisations.
This suggests that the significance of a property is partly relational.
A property tells us something about what an entity is capable of doing.
An environment determines which of those capacities can become consequential.
Possibility is not probability
There is another distinction we need to make.
When we speak of possibility here, we are not simply talking about probability.
A possibility is not necessarily an event that is likely to occur.
A possibility is something that can occur under appropriate conditions.
This matters because physical reality is full of possibilities that are never actualised.
The chemical possibilities of an electron are vastly greater than the particular reactions in which any given electron will participate.
The electromagnetic spectrum contains an enormous range of possible frequencies, even though a particular source may produce only a small portion of them.
A molecule may be capable of many reactions that never occur.
An organism may possess capacities that its environment never calls upon.
Possibility therefore introduces a distinction between:
what happens
and
what could happen.
Physics is extraordinarily good at describing actual states and the laws governing their transitions.
But the laws also implicitly describe a space of possible states and transitions.
The possibilities are not necessarily visible in any particular event.
They are encoded in what the system is capable of doing.
The laws do more than describe what happens
This gives us a slightly different way of thinking about physical laws.
We usually think of a law as telling us what happens.
Given these conditions, this is the result.
But a law also tells us what cannot happen.
And, just as importantly, it tells us what remains available as a possibility.
Conservation laws exclude enormous numbers of imagined events.
Symmetries constrain what interactions can occur.
Quantum statistics constrain how particles can be arranged.
The structure of the electromagnetic interaction determines which physical processes are available and which are not.
So physical law does not merely govern actuality.
It shapes the space of possibility within which actuality unfolds.
This is important for the project we are beginning.
Because if we want to understand what a particle makes possible, we cannot simply catalogue its properties. We have to understand the constraints within which those properties operate.
A possibility is never just something that could happen in the abstract.
It is something that can happen given a particular organisation of constraints and capacities.
Constraints do not merely restrict possibility
This may seem paradoxical.
We tend to think of constraints as reducing possibility.
If something is constrained, fewer things can happen.
That is true in one sense.
But constraints can also make new forms of possibility possible.
A completely unconstrained collection of particles has enormous freedom but very little organisation.
A constraint can stabilise a pattern.
A stable atomic structure depends upon constraints.
A molecule depends upon constraints.
A crystal depends upon constraints.
A living organism depends upon extraordinarily elaborate constraints.
The constraint does not simply remove possibilities.
It selects a region of possibility in which a new kind of organisation can exist.
This is why a structure can be more than a restriction.
It can be an enabler.
A molecule is constrained in ways that allow it to possess a stable identity.
A cell membrane constrains the movement of substances across it, but that very restriction makes a chemically differentiated interior possible.
A biological organism is constrained by its physical structure, yet those constraints make possible capacities such as metabolism, movement and perception.
So perhaps we should modify our earlier sequence:
property → capacity → constraint → organisation → possibility
The addition of constraint is not incidental.
It may be one of the mechanisms through which new possibilities arise.
The strange productivity of constraint
Consider a language.
Its grammar imposes constraints.
There are sentences we cannot form, or that become unintelligible if we violate certain grammatical relationships.
Yet these constraints do not impoverish language.
They make an enormous space of expression possible.
The rules of a musical scale similarly restrict the available notes, but they enable structures that would not exist as music without those relationships.
A chessboard constrains movement radically, yet within those constraints an astonishing space of possible games appears.
These examples are not physics.
But they illuminate something that may already be present in physical organisation.
A constraint can transform a diffuse space of possibilities into a structured one.
It can make some possibilities unavailable while making other, more organised possibilities accessible.
Perhaps this is one reason why complexity does not simply arise by accumulating more components.
It arises when components become constrained into productive relationships.
The atom as a possibility machine
The atom provides a beautiful physical example.
An atomic nucleus and its electrons are not simply a collection of particles occupying the same place.
Quantum mechanics imposes a structure on the possible states of the system.
Electrons cannot simply pile into the same state without regard to the relevant quantum rules. The resulting structure gives atoms characteristic configurations and energies.
And because atoms possess these structures, they can interact with other atoms in systematic ways.
The atom therefore becomes something more than a container for particles.
It becomes a new physical organisation with new capacities.
The possibilities available to an atom are not merely the sum of the possibilities available to an isolated nucleus and an isolated electron.
The organisation itself matters.
This is one of the first places where our vocabulary of possibility begins to illuminate emergence.
The atom is not mysterious.
Nothing supernatural has appeared.
But something genuinely new has become possible.
Possibility accumulates
Now imagine continuing upward.
Atoms form molecules.
Molecules can form polymers and complex materials.
Certain molecular arrangements can participate in chemical cycles.
Some chemical networks can sustain themselves by exchanging matter and energy with their surroundings.
Under the right historical circumstances, some become capable of reproduction and heritable variation.
Now evolution can operate.
And once evolution begins, the space of realised possibilities expands again.
Eyes become possible.
Wings become possible.
Nervous systems become possible.
Languages become possible.
Computers become possible.
None of these possibilities was present as a miniature object at the beginning.
The universe did not contain a tiny eye waiting inside the photon, or a tiny language waiting inside the electron.
Instead, possibilities accumulated through organisation.
This is perhaps a more useful way of thinking about emergence.
The emergence of something new does not require that the new thing was already hidden inside its constituents.
It requires that the constituents possess capacities that can be organised in ways that open a new region of possibility.
The world as a landscape
We can now return to the metaphor introduced in the previous essay.
Perhaps reality is not adequately represented by a list of things.
Perhaps it is better represented as a landscape of possibilities shaped by properties, relations and constraints.
Some regions of that landscape are physically inaccessible.
Some are unstable.
Some are extraordinarily unlikely.
Some are easy to reach.
And some become accessible only after other structures have formed.
The important point is that the landscape itself changes as organisation changes.
Once atoms exist, molecular possibilities become available.
Once molecules exist, chemical networks become available.
Once living systems exist, evolutionary possibilities become available.
Once nervous systems exist, new forms of behavioural and informational organisation become available.
Once symbolic systems exist, entirely new forms of cultural organisation become available.
The universe is not merely travelling through a pre-existing list of possibilities.
Rather, new domains of possibility can become available as organisation develops.
That is a much stronger claim.
And it is also a more difficult one.
Does the possibility already exist?
Here we encounter a philosophical problem.
If a species evolves eyes, were eyes always possible?
In one sense, yes.
The physical laws did not suddenly change when eyes appeared.
The relevant physical conditions were already compatible with the eventual existence of eyes.
But in another sense, saying that "eyes were always possible" can be misleading.
There was no eye-shaped possibility waiting somewhere in the universe like an item on a cosmic menu.
The particular pathway by which eyes emerged depended upon contingent histories, environments, mutations, developmental systems and evolutionary selection.
What existed beforehand were capacities and constraints from which such a possibility could eventually be realised.
This distinction may prove central to the whole series.
We might call the first kind of possibility latent possibility: what the physical organisation permits.
The second is generated possibility: what becomes accessible only after further organisation has occurred.
The distinction is not absolute, but it gives us a useful question:
Does reality merely realise possibilities, or can new forms of possibility themselves emerge?
The possibility of possibility
That question may sound unnecessarily grand.
But consider what happens when a new organisation appears.
Before the atom, there is no chemistry.
Before chemistry, there is no metabolism.
Before metabolism, there is no organism that can exploit an environment.
Before sensory systems, there is no organism for which electromagnetic differences can function as environmental information.
The later possibility depends upon the earlier organisation.
This means that the history of the universe can be viewed, at least in part, as a history of new spaces of possibility becoming accessible.
That does not mean that the universe is striving toward complexity.
It does not mean that life was inevitable.
It does not mean that consciousness was secretly encoded in matter.
It means something more modest:
When physical capacities become organised in new ways, the set of things that can happen can change.
And that may be enough to give us a powerful new way of asking about emergence.
From particles to worlds
We began with an electron's charge.
It seemed like a property.
But follow its consequences and we encounter electromagnetic interaction, atomic structure, chemistry, molecular organisation and eventually biological complexity.
The charge has not changed.
What changes is the organisation in which that property participates.
This suggests that we should not think of physical properties as isolated possessions.
A property is also a potential participant in a world of relations.
Its significance depends upon what it can encounter, what it can interact with, what constraints it can enter into, and what organisations those interactions can sustain.
The same general thought applies to the photon.
Its physical properties make electromagnetic interactions possible.
Those interactions make energy transfer and detection possible.
Biological organisation makes some of those detections environmentally significant.
And eventually, organisms can build elaborate systems around those distinctions.
At each stage, something that was previously merely a physical capacity becomes an enabling condition for something richer.
A new question for physics
Perhaps, then, the question we should carry forward is not simply:
What properties does a particle have?
but:
What possibilities do those properties open?
And then, immediately:
What conditions are required for those possibilities to become actual?
That second question prevents us from turning possibility into a mystical substance.
A possibility is not a ghostly object waiting in the future.
It is a relation between capacity and conditions.
The electron can participate in chemical organisation, but only in the right physical circumstances.
The photon can provide information to an organism, but only if there is an organisation capable of detecting and interpreting the relevant differences.
The possibility therefore lies neither wholly in the particle nor wholly in the environment.
It lies in the relation between them.
And that may be the first genuinely ecological insight of our investigation.
What becomes possible?
We began this series by asking what a particle does.
We can now sharpen the question.
A particle has properties.
Those properties give it capacities.
Capacities enter into interactions.
Interactions become organised under constraints.
Organisations possess new capacities.
Those capacities open new possibilities.
And those possibilities can become the conditions for further organisation.
So perhaps the history we are beginning to trace is not simply:
particle → atom → molecule → organism
but:
property → capacity → relation → organisation → possibility → new capacity → new possibility.
The arrow matters.
The point is not merely that one thing follows another.
The point is that each stage can alter what becomes possible at the next.
That gives us a rather different image of physical reality.
It is not a static inventory of entities.
It is a world in which capacities can enter into relationships, relationships can become organised, and organisations can open doors that did not previously exist.
We may therefore have to revise our initial question once more.
Not:
What does a particle do?
And not even:
What does a particle make possible?
But:
What becomes possible because a particle can do what it does?
That question takes us from the particle toward the atom.
And the atom is where the next part of our story becomes particularly interesting.
Because the atom does something the isolated particle cannot do:
it begins to turn physical possibility into structure.
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