If Bohm preserves determinacy by insisting that the world is fully specified, and Many Worlds preserves it by ensuring that nothing is ever excluded, QBism preserves quantum theory by refusing to say what the world is at all.
Quantum States as Belief States
QBism begins with a radical reinterpretation of the quantum state. The wavefunction does not describe a physical system. It encodes an agent’s expectations about the outcomes of their future experiences.
Collapse is not a physical event, nor even a perspectival cut in the world. It is a change in the agent’s bookkeeping.
Quantum mechanics, on this view, is a normative guide for how rational agents should manage uncertainty when acting in the world.
What that world is, beyond its resistance to expectation, is left unspecified.
Saving Agency by Sacrifice
QBism’s motivation is clear and admirable.
It refuses the fantasy of a view from nowhere. It rejects the idea that quantum states exist independently of those who assign them. It takes seriously the role of the agent as irreducible.
But the price of this move is also clear.
In order to secure agency, QBism evacuates ontology.
The world becomes a source of surprises, not a structured field of potential. Relations collapse into personal expectation. Shared reality survives only as a constraint on belief revision.
The Relational Question
Relational ontology agrees with QBism on a crucial point: quantum states are not properties of systems.
But it parts company immediately on what follows.
The relational challenge is therefore this:
What if probability belongs neither to the world nor to the agent, but to the relation that makes instantiation possible?
Probability as Readiness
It is an expression of readiness: the structured openness of a system, under a given construal, to actualise in particular ways.
QBism collapses probability into belief because it has no place to locate readiness except in the agent’s head.
Relational ontology insists that readiness is real — but not independent of construal.
The World Reduced to Resistance
QBism often speaks of the world as that which “pushes back” against the agent. Experience is real. Outcomes occur. Surprises happen.
But these surprises are not expressions of a shared field of potential. They are merely constraints on expectation.
What is lost is precisely what quantum theory made visible: that outcomes are not arbitrary interruptions of belief, but actualisations from a structured domain of possibility.
Without that domain, experience becomes brute.
The Cost of Personalisation
QBism succeeds in dissolving many traditional puzzles. There is no measurement problem if nothing is being measured about the world. There is no collapse problem if collapse is merely belief update.
But this success is purchased by withdrawing any account of how multiple agents inhabit the same reality — except by coincidence and negotiation.
The world becomes something we bump into, not something we co-constitute.
Between Objectivity and Subjectivity
Relational ontology refuses the trade QBism offers.
QBism protects the agent by abandoning the world.
Relational ontology insists that the world itself is relational — not something agents describe, but something that comes into being through cuts that are neither purely subjective nor purely objective.
The Cost of Withdrawal
QBism is a disciplined refusal. It refuses to speak where speaking would mislead. It protects quantum theory from metaphysical excess by saying less.
Relational ontology names the cost of that restraint.
By removing probability from the world, QBism removes possibility from it as well. What remains is experience without becoming, belief without readiness, and a reality that can surprise but not mean.
The cut survives — but only inside the agent.
What is lost is the field in which possibility itself can become.
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