What are the physical requirements for agency? We investigate whether a purely quantum system (one evolving unitarily in a coherent regime without decoherence or collapse) can satisfy three minimal conditions for agency: an agent must be able to create a world-model, use it to evaluate the likely consequences of alternative actions, and reliably perform the action that maximizes expected utility. We show that the first two conditions conflict with the no-cloning theorem, which forbids copying unknown quantum states: world-model construction requires copying information from the environment, and deliberation requires copying the world-model to assess multiple actions. Approximate cloning strategies do not permit sufficient fidelity or generality for agency to be viable in purely quantum systems. The third agency condition also fails due to the linearity of quantum dynamics. These results imply four key consequences. First, agency requires significant classical resources, placing clear constraints on its physical basis. Second, they provide insight into how classical agents emerge within a quantum universe. Third, they show that quantum computers cannot straightforwardly simulate agential behavior without significant classical components. Finally, they challenge quantum theories of agency, free will, and consciousness.
What are the physical requirements for agency? We investigate whether a purely quantum system (one evolving unitarily in a coherent regime without decoherence or collapse) can satisfy three minimal conditions for agency: an agent must be able to create a world-model, use it to evaluate the likely consequences of alternative actions, and reliably perform the action that maximizes expected utility. We show that the first two conditions conflict with the no-cloning theorem, which forbids copying unknown quantum states: world-model construction requires copying information from the environment, and deliberation requires copying the world-model to assess multiple actions. Approximate cloning strategies do not permit sufficient fidelity or generality for agency to be viable in purely quantum systems. The third agency condition also fails due to the linearity of quantum dynamics. These results imply four key consequences. First, agency requires significant classical resources, placing clear constraints on its physical basis. Second, they provide insight into how classical agents emerge within a quantum universe. Third, they show that quantum computers cannot straightforwardly simulate agential behavior without significant classical components. Finally, they challenge quantum theories of agency, free will, and consciousness.
What are the physical conditions required for agency? Recent work has rigorously shown that purely unitary, coherence-preserving quantum dynamics are insufficient to support deliberation, comparison of counterfactual actions, and reliable action selection. These results establish a genuine no-go theorem for agency in a strictly quantum-coherent regime. This paper provides a structural completion of that no-go result. Rather than challenging its correctness, the analysis identifies the underlying assumption on which it rests: that unitarity alone is sufficient as an admissibility criterion for decision endpoints. We show that this assumption is incomplete. Working within the Tier-0 closure framework, physical lawfulness is characterized by closure-stable fixed points selected by structural constraints rather than by unconstrained dynamical evolution. Within this framework, coherent quantum states may function as intermediate computational or representational states but are excluded as lawful endpoints for records, decisions, and control. Applying closure stability to quantum systems yields a classical decision subspace without introducing new dynamics, observer-dependent postulates, or interpretation-specific assumptions. The paper further shows that agency requires a closure-stable internal selection process capable of consistent expected-utility comparison. Imposing closure compatibility rigidly fixes the standard quadratic Born probability rule as the only weighting compatible with stability, representation-independence, and admissibility-preserving re-expression. Together, these results integrate agency into the same structural framework that accounts for quantum measurement and probability. The absence of agency in purely quantum-coherent models is shown to reflect an under-constrained admissibility regime rather than a fundamental limitation of quantum theory. Lawful agency emerges as a closure-stable property of coupled agent–world dynamics, fully consistent with standard quantum mechanics. This work clarifies the physical limits of purely quantum models of decision, sharpens existing no-go arguments, and provides a mathematically explicit foundation for agency grounded in structural admissibility rather than interpretation.
Darwinian evolution requires (i) heritable records, (ii) repeatable copying with variation, and (iii) routine irreversibility. Categorical quantum mechanics (CQM) makes precise why ``copy'' and ``delete'' are not generic quantum operations: they exist only for a realized \emph{classical data} sector (a preferred basis/observable; a commutative structure). Decoherence explains how a pointer basis can be selected dynamically, but it does not by itself select a unique outcome. This motivates a neutral presentation of the main ontological options (unique-history, decohered multiplicity, agent-relative facticity, and a stochastic foundation with variable diffusion). We also note the relevance of the ``agency constraint'' argued by Adlam-McQueen-Waegell: in a strictly coherent, basis-unselected ``purely quantum'' regime, minimal agency fails due to no-cloning and linearity, which sharpens the role of classical resources for record-based processes. Extended Wigner's Friend scenarios then serve as a stress test, since they treat ``friends'' simultaneously as coherent quantum systems and as agents possessing stable records. Finally, a stochastic-mechanics foundation (with variable diffusion) offers a continuous bridge between quantum and classical regimes, and suggests a principled way to implement measurement update as conditioning plus a time-symmetric minimal-change rule.
What are the physical conditions required for agency?Recent work has rigorously shown that purely unitary, coherence-preserving quantum dynamics are insufficient to support deliberation, comparison of counterfactual actions, and reliable action selection. These results establish a genuine no-go theorem for agency in a strictly quantum-coherent regime.This paper provides a structural completion of that no-go result. Rather than challenging its correctness, the analysis identifies the underlying assumption on which it rests: that unitarity alone is sufficient as an admissibility criterion for decision endpoints. We show that this assumption is incomplete.Working within the Tier-0 closure framework, physical lawfulness is characterized by closure-stable fixed points selected by structural constraints rather than by unconstrained dynamical evolution. Within this framework, coherent quantum states may function as intermediate computational or representational states but are excluded as lawful endpoints for records, decisions, and control.Applying closure stability to quantum systems yields a classical decision subspace without introducing new dynamics, observer-dependent postulates, or interpretation-specific assumptions. The paper further shows that agency requires a closure-stable internal selection process capable of consistent expected-utility comparison. Imposing closure compatibility rigidly fixes the standard quadratic Born probability rule as the only weighting compatible with stability, representation-independence, and admissibility-preserving re-expression.Together, these results integrate agency into the same structural framework that accounts for quantum measurement and probability. The absence of agency in purely quantum-coherent models is shown to reflect an under-constrained admissibility regime rather than a fundamental limitation of quantum theory. Lawful agency emerges as a closure-stable property of coupled agent–world dynamics, fully consistent with standard quantum mechanics.This work clarifies the physical limits of purely quantum models of decision, sharpens existing no-go arguments, and provides a mathematically explicit foundation for agency grounded in structural admissibility rather than interpretation. https://doi.org/10.5281/zenodo.18028427
Creating machines that are conscious is a long term objective of research in artificial intelligence. This paper look at this idea with new arguments from physics and logic. Observers have no place in classical physics, and although they play a role in measurement in quantum physics there is no explanation for their emergence within the framework. There is suggestion that consciousness, which is implicitly a property of the observer, is a consequence of the complexity of specific brain structures, but this is problematic because one associates free will with consciousness, which goes counter to causal closure of physics. Considering a nested physical system, we argue that even if the system were assumed to have agency, observers cannot exist within it. Since complex systems can be viewed in nested hierarchies, this constitutes a proof against consciousness as a product of complexity, for then we will have nested system of conscious agents. As the existence of consciousness in cognitive agents cannot be denied, the implication is that consciousness belongs to a dimension that is not physical and machine consciousness is unattainable. These ideas are used to take a fresh look at two well-known paradoxes of quantum theory that are important in quantum information theory.
World models provide digital simulacra of the true world, allowing agents to be trained and tested before costly real-world deployment. At each time step, they receive an action and generate an observation and reward matching the statistics of the true world. In complex environments where present outcomes depend on events far in the past, this requires memory. One might expect that, by increasing memory, we can always build a model accurately enough to align the optimal agent policies of the real and virtual worlds. We show that this is false for classical world models, even when the true world itself is classical. We construct true worlds for which every finite classical model fails along the same possible trajectory: it either loses the ability to distinguish actions when the true world clearly prefers one, or repeatedly assigns the highest expected reward to suboptimal actions. Its expected-reward estimates also retain a nonvanishing average error. In contrast, each such true world admits a quantum world model using a single qutrit that reproduces it exactly: its reward estimates and preferred actions always match those of the true world, ensuring that the optimal policies of the real and virtual worlds remain perfectly aligned.
Quantum decision theory is a theory of choice behavior, and as such deals not just with Cognition but also with what I have separated out as Will. However, its advocates have concentrated on demonstrating that quantum preferences and beliefs, conceived as a kind of input, can predict observed behavioral outputs. As a result, they have not thematized what is going on in-between, the mechanism (sic) by which the quantum mind makes choices in the first place. In this way the theory, like its classical forerunner, selects a “basis vector” for thinking about people that is more on the terrain of Cognition than of Will. That makes sense as a first step, given that if the theory can't predict behavior then the rest is moot, but to get a more rounded quantum person we need to “rotate” to the basis of Will. Will is the essence of agency, a power to animate and move the body – and the mind, in the form of attention – from the essentially passive stance of Cognition to active, purposeful engagement with the world. In Chapter 6, I equated this power with an aspect of wave function collapse, viewed as a process of temporal symmetry-breaking, in which advanced action moves through Will and retarded action through Experience. (Note that this means Will is not straightforwardly conscious, to which I return below.) If that is right, then Will and Experience are complementary in the quantum sense – incompatible, yet jointly necessary for a complete description of the collapse process – and so it will only be after reading the next chapter that the meaning of this one will be fully realized. If Will is an aspect of wave function collapse – one of the most incomprehensible features of quantum mechanics – then that may help explain why, compared to Cognition and even Experience, its standing among philosophers seems more tentative.