AJ van Hoek

Health, knowledge, trust, the living world: what keeps us alive is held in common, and lasts only as long as we keep tending it.

That work has a name, commoning. I do it as a scientist at RIVM, and in my independent work on how we keep existing together.

A disease can only go where we have gone to each other. The lines fray with death, parting and distance, and are spun again by birth, love and kinship. Epidemiology reads what they leave behind: a quiet record of affection, of contact, of how much we need one another.

Click to add someone.

Work

I am a senior scientist at RIVM, the Dutch National Institute for Public Health and the Environment, working on infectious disease epidemiology, modelling and health economics. I lead Infectieradar, the Dutch participatory surveillance cohort and part of the European Influenzanet network, in which people report their own symptoms every week.

Along the way I have worked on the carriage dynamics of pneumococcus and meningococcus, on simulation-based inference for epidemics in structured populations, and on natural language processing.

Looking ahead, three things drive my work:

  • Open infrastructure for public health research. We build CASE, an open-source project for survey-based research, with Case Survey and related versions built on it.
  • AI in the daily workflow. Bringing natural language processing and AI into how surveillance and research are done.
  • Evidence for decisions. Surveillance and cost-effectiveness analysis that gives decisions in public health a sound basis.

Independent work

What can we stand on, if the only certainty is that we can be wrong?

Learning. If we can be wrong, we have to keep learning, and we cannot learn alone.

Alongside my work at RIVM, I have spent most of my life on that question. It began with the Room: if sincere certainties can exclude each other, then certainty is not a guarantee of truth. I came out of it fundamentally non-certain.

But non-certainty turned out not to be a void. It is a starting point. If you can be wrong, you have to keep testing your picture of the world against what you cannot control, and change it when it fails. Each of us lives in our own model of reality; what we can still share is the work of correcting it. And that correction arrives through others: the people, the evidence and the feedback around you.

My work builds this out as Evolution by Emergence, a theory of persistence that starts from learning in a network. In a world that changes, whatever lasts does so by changing with it, through its connections. It draws on what is held in common, and lasts only while it lives off the interest, not the principal. We do not exist on our own.

I explore what follows from this from five perspectives, all resting on one foundation: the Room.

Every room opens onto the Room. A door between two rooms marks where one perspective directly depends on another. Choose a room to enter it.

The Room

The foundation

Three people sit in a room. One is certain of A, one of B, one of C, and the three cannot all be true together. You do not need to know who is right to know that at least two of them are wrong. And the ones who are wrong feel exactly as certain as the one who is right.

I first thought of this when I was about twenty, and it has stayed with me ever since. The logic is trivial; what follows from it is not. Certainty is a state of mind, not a guarantee of truth. I have held certainties myself that I later rejected with the same conviction.

As a mind you are a model of the world, not the world, so you can be wrong, even about your strongest belief. That fact makes everything else important. It means that you exist in relation: to the people, the evidence and the corrections that keep your model in touch with the world.

Status The logical core is machine-checked in Lean. What it implies for people and institutions is argued, not proven.

Ecological

How do we keep existing?

From metabolism to ecosystems, intelligence and society.

A living organism does not exist independently of its surroundings. It needs energy, matter and continuous exchange to keep itself going.

But those surroundings are themselves the result of processes. Bacteria, fungi, plants and animals change the world in which other organisms live. Individual metabolisms become part of larger cycles.

So the whole is not a fixed backdrop against which life plays out. It is continually shaped by the very organisms that depend on it.

My research, Evolution by Emergence, explores whether such patterns can be described by a more general model. It asks how organisations of interdependent processes manage to last, how changes are retained, and how new possibilities arise.

Part of this is the idea of the commons: the shared resources, processes and conditions on which the functioning of each separate part depends.

An important question is whether we recognise similar mechanisms at different scales, from cells and organisms to intelligence and human organisations, and where that comparison breaks down.

Central questions

  • What makes a system viable?
  • How do mutual dependencies arise?
  • When do processes strengthen each other, and when do they exhaust each other?
  • How does the survival of a part relate to the survival of the whole?

Status Formal results under stated premises, partly machine-checked in Lean. Whether real systems meet those premises, and where the comparison across scales fails, is open.

Economic

How do we share what we produce?

From individual prices to the organisation of shared production.

Our economy is a vast network of interdependent activities. Almost nothing we use was produced entirely by one person or one organisation.

Yet companies usually make decisions about price and production from their own position. Sometimes it pays a supplier more to sell less at a higher price, even when many more people could be helped at a low extra cost.

That is why I am exploring an alternative pricing model. It separates the cost of making something available from the reward for solving the problem that made it available.

In this model, costs, margins, external effects and rewards are each made visible. A solution can be offered widely, while whoever developed it receives an explicit reward. The model is meant to work along whole production chains, without needing a central planner.

This is not a plea to ignore scarcity, risk, the cost of innovation, or property rights. It is an attempt to make the different economic functions of prices and profits more explicit, so that their consequences can be studied.

Central questions

  • What does something really cost?
  • Who pays for the consequences that are not in the price?
  • How do we reward innovation without needlessly restricting access?
  • Which incentives support lasting availability and maintenance?

Status A worked-out research proposal with formal results under explicit assumptions, machine-checked in Lean. Whether such systems work better in practice has to be tested empirically.

Cultural

How do we understand and live our existence?

From scientific insight to identity, stories, music and ritual.

Science helps us understand how something works. But people do not live by explanations alone. We also live by stories, values, habits, emotions, music and shared meanings.

What happens to our self-image when we come to understand ourselves as learning processes?

From that question I am developing Disco ergo sum: I learn, therefore I am. From it grew Discovarianism, a playful and serious exploration of what it means to recognise yourself as a learning being.

If my picture of reality is fallible, doubt is not only a weakness. It can be an opening to new knowledge. And if I depend on other people, then honesty, listening, responsibility and the chance to repair mistakes are not just social conventions. They are essential parts of how I learn.

I do not explore these ideas only in philosophical texts. I also use music, stories, humour and symbolism. Music can do something a formal proof cannot: evoke an experience. A song can make you feel the tension between two people who live through the same thing but understand it differently. I write and produce songs as Emergence.

Discovarianism does not claim that a scientific theory automatically yields a complete morality or religion. It is a cultural experiment: what kind of attitude to life could grow from this self-understanding, and which values do we consciously choose along the way?

Central questions

  • How does our behaviour change when our self-image changes?
  • Can curiosity and correctability become part of a culture?
  • What role do joy, beauty, wonder and ritual play in how people learn?

Status A cultural experiment. Some of its lines follow from being a learning process; others are values, chosen and named as such.

Epistemic

How do we know what is true?

From individual beliefs to science, AI and shared world models.

We have no unlimited, direct access to reality. We try to understand it through observations, experiences and models.

Those models help us think ahead and act, but they can be incomplete or wrong. And two people with different experiences can come to hold different beliefs.

So I study not only what we know, but above all how we know, learn and correct.

An important distinction is between a world model and a functional world model. Someone can hold an entirely convincing story about reality that is nonetheless wrong. A functional world model must therefore be tested against information it does not itself determine, represent its uncertainty fairly, and keep correction possible.

That becomes harder once knowledge arises collectively. In science, in organisations and in AI systems, different contributions are combined. But how? What if one wrong contribution affects the whole? What if everyone relies on the same source? And what if dissenting perspectives disappear before their value becomes clear?

Differing views are not necessarily a problem to be solved as quickly as possible. They can help reveal hidden assumptions and errors. In my work I therefore explore how individual and collective world models develop, how correction can be preserved, and how human and artificial intelligence can examine each other's insights.

Central questions

  • How do we recognise our own mistakes?
  • How do we preserve independent perspectives?
  • When is consensus helpful, and when is it dangerous?
  • How do we design systems that can revise their knowledge without making earlier mistakes invisible?

Status A definition note, reviewed three times. One narrow part of it is machine-checked in Lean; practices and a checklist are still to come.

One open inquiry

These five perspectives are not separate islands.

Ecological systems provide the conditions for economic and social life. Economic structures help determine how those conditions are used and maintained. Law protects freedoms and limits power. Culture shapes what people find important. And our world models shape how we understand and change all of these systems.

At the same time, the perspectives can clash. What is economically efficient need not be ecologically sustainable. What sustains a collective need not be just to every individual. What seems self-evident within a culture need not be true.

So I do not try to fold every perspective into one answer decided in advance. I study their similarities, their differences, their dependencies and their limits.

What is proven, and what remains open?

Part of this work consists of mathematical models and formal proofs, some of them in Lean. Other parts are research proposals, conceptual explorations, hypotheses to be tested, or values chosen explicitly. I think that distinction matters.

A proof inside a formal model does not prove that the world meets the model's assumptions.

And a description of how systems last does not tell us which systems we ought to preserve. The work is therefore open to criticism, extension, testing and revision.

Exploring together

I want this work to be accessible to people who come to similar questions from very different disciplines: biologists, economists, lawyers, philosophers, artists, designers, musicians, programmers, and anyone else who is curious.

Some will want to test the theory. Others will see applications, counterexamples, missing perspectives, or ways to make the ideas something you can experience. I am interested in all of these.

Not because we should all end up thinking the same, but because another perspective sometimes lets us discover what we could not see from our own.

We can be wrong. Let us find out together.

Elsewhere