This paper argues that the traditional opposition between determinism and indeterminism in physics is representational rather than ontological. Deterministic-stochastic dualities are available in principle, and arise in a non-contrived way in many scientifically important models. When dynamical systems admit mathematically equivalent deterministic and stochastic formulations, their observable predictions depend only on the induced structure of correlations between preparations and measurement outcomes. I use this model-equivalence to motivate a model-invariance criterion for ontological commitment, according to which only structural features that remain stable across empirically equivalent representations, and whose physical effects are invariant under such reformulations, are candidates for realism. This yields a fallibilist form of structural realism grounded in modal robustness rather than in the specifics of any given mathematical representation. Features such as conservation laws, symmetries, and causal or metric structure satisfy this criterion and can be encoded in observable relations in mathematically intelligible ways. By contrast, the localisation of modal selection -- whether in initial conditions, stochastic outcomes, or informational collapse mechanisms -- is not invariant under empirically equivalent reformulations and is therefore best understood as a gauge choice rather than an ontological feature. The resulting framework explains how certain long-standing problems in the foundations of physics, including the measurement problem and the perceived conflict between physical determinism and free agency, arise from the reification of representational artefacts. By distinguishing model-invariant structure from modelling conventions, I offer a realist ontology for modern physics that combines empirical openness with resistance to metaphysical overreach.
This paper argues that the traditional opposition between determinism and indeterminism in physics is representational rather than ontological. Deterministic-stochastic dualities are available in principle, and arise in a non-contrived way in many scientifically important models. When dynamical systems admit mathematically equivalent deterministic and stochastic formulations, their observable predictions depend only on the induced structure of correlations between preparations and measurement outcomes. I use this model-equivalence to motivate a model-invariance criterion for ontological commitment, according to which only structural features that remain stable across empirically equivalent representations, and whose physical effects are invariant under such reformulations, are candidates for realism. This yields a fallibilist form of structural realism grounded in modal robustness rather than in the specifics of any given mathematical representation. Features such as conservation laws, symmetries, and causal or metric structure satisfy this criterion and can be encoded in observable relations in mathematically intelligible ways. By contrast, the localisation of modal selection -- whether in initial conditions, stochastic outcomes, or informational collapse mechanisms -- is not invariant under empirically equivalent reformulations and is therefore best understood as a gauge choice rather than an ontological feature. The resulting framework explains how certain long-standing problems in the foundations of physics, including the measurement problem and the perceived conflict between physical determinism and free agency, arise from the reification of representational artefacts. By distinguishing model-invariant structure from modelling conventions, I offer a realist ontology for modern physics that combines empirical openness with resistance to metaphysical overreach.
Dualities in physics have challenged traditional forms of scientific realism by undermining the idea that theories describe a unique underlying ontology. In this paper, we develop a new perspective on scientific realism that responds to this challenge. We argue that while realist commitment remains appropriate at the level of a theory's full formal structure, ontological commitment should be treated as tied to specific empirical contexts rather than to a fixed, real ontology. Our proposal draws inspiration from Dennett's notion of a "compression algorithm" as a defining criterion of a scientific theory. On this basis, we separate realism from ontological commitment. To clarify the stakes of this distinction, we contrast our approach with common core realism, which locates ontology in the invariant structure shared by dual models. Focusing on dualities in quantum mechanics and string theory, we show how our view accommodates ontological pluralism while preserving a robust form of structural realism.
Abstract: The classical architecture of physical science and analytic metaphysics has often been associated with deterministic necessitarianism, according to which a complete specification of antecedent conditions and governing laws uniquely determines subsequent physical states. The advent of quantum mechanics challenges this picture without thereby implying unconstrained modal chaos. This paper develops a tripartite modal framework comprising Strong PSR (S), Unconstrained Contingency (U), and Structured Contingency (W). Let P denote the broad domain of logically and mathematically formulable physical configurations, and A the subset physically realizable under the relevant nomological framework. Structured Contingency is defined as W⟺(∣A∣>1)∧(A⊊P). Using a dual-front methodology, the paper first draws deductive consequences from two empirically grounded premises: quantum openness (E1), represented by ∣A∣>1, and structural constraint (E2), represented by A⊊P. Together these yield the formal synthesis E1∧E2⊢W, while E1 independently excludes Strong PSR under the framework's specified modal interpretation. The paper then conducts a comparative abductive evaluation of W against Unconstrained Contingency, arguing that W provides superior descriptive adequacy and explanatory parsimony because it accommodates genuine physical plurality while preserving the objective structural regularities exhibited by quantum theory. The resulting Lemma of Structured Contingency is offered not as a new mathematical theorem, but as a formal synthesis of modal plurality and nomological constraint. The framework thus provides an analytically austere account of physical modality as simultaneously open and structurally bounded.
Physical systems often exhibit stable, repeatable regimes despite being described by equations that allow many possible trajectories. This tension is typically addressed using probabilistic language, with probability treated as a fundamental feature of evolution or as a reflection of stochastic dynamics. In this paper, we argue that probabilistic descriptions instead arise from structural underdetermination in the presence of recurrence and finite resolution. We introduce a coherence-first account in which repeated traversal of structurally admissible pathways reinforces regime stability, leading to effective regime selection without invoking randomness, agency, or additional dynamical mechanisms. Within this framework, probability collapse is not a physical event but a resolution of indistinguishability as recurrence deepens constraint. This perspective completes a structural notion of determinism: outcomes need not be fixed, but admissible regimes are finite, and repeated evolution naturally sharpens their dominance. The resulting picture reconciles deterministic dynamics with probabilistic description while preserving consistency with existing physical formalisms.
Observer-Equivariant Ontology (v1) develops a compact ontological and methodological stance tailored to modern physics: the fundamental objects are not “systems in themselves” but observer perspectives related by symmetry. The paper formulates this as an equivalence requirement across admissible perspectives and uses it to motivate why the epistemic core of physics is structurally invariant content (relations, constraints, symmetries), rather than observer-dependent representations. The text is written as a conceptual companion to the more technical parts of the series. It clarifies: (i) what is being quantified over when physics speaks about “observers” or “frames”, (ii) how invariance and gauge redundancy enter as structural constraints on admissible descriptions, and (iii) how a perspective-based ontology can be stated without committing to instrumentalism. Where needed, the paper points to the technical manuscripts for constructions such as symmetry-constrained measures and history groupoids. This upload is version v1 of the paper. Version DOI (this record): 10.5281/zenodo.17929468 Series DOI (all versions): 10.5281/zenodo.17929467
In previous chapters we argued that the empirically successful formalism of quantum mechanics supports equally well two mutually incompatible general ontologies: the inherently indeterministic and generally accepted Copenhagen interpretation and Bohm's completely deterministic one. This underdetermination of the interpretation by the formalism is not simply an apparent one of two equivalent theories since there is no way to translate the terms of one of these ontologies into those of the other. This case could be seen as presenting a challenge to the scientific realist who seeks from successful scientific theories a true representation of the world. Furthermore, we suggest that the actual historical competition between these theories and the selection of Copenhagen over Bohm illustrate that such an historically contingent process is not meaningfully distinct from the rational reconstruction and logical judgment of the victorious theory. What is deemed successful and put on offer by the scientific community for the philosopher of science to justify after the fact is itself a contingent and nonunique product. UNDERDETERMINATION The origin of the underdetermination of scientific theories, what we refer to here as the so-called Duhem–Quine thesis, is typically located in Pierre Duhem's The Aim and Structure of Physical Theory (first published in 1906). There Duhem was quite explicit about what he took to be the basis for judging whether or not a given physical theory is acceptable.
We challenge the common view that relativity and quantum formalisms compel a static block-universe ontology. Instead, we show that Existential Realism (ER) – can be formulated as an ontological extension of the specific physical models studied here, leaving empirical predictions unchanged so long as the added ER structure remains empirically idle. First, we clarify that the mathematical formalism of physics is neutral: one can impose a preferred foliation or an existence predicate without changing the equations. Second, we explicitly construct ER-compatible models for Minkowski spacetime (special relativity) and a finite-dimensional quantum system. In these Minkowski-spacetime and finite-dimensional quantum toy models, we show that the standard relativistic dynamical laws, Born-rule calculations, and unitary evolution between measurements are preserved, while the ER additions remain extra ontological structure. More precisely, we have constructed models that are empirically equivalent and dynamically identical while differing in their ontological assignments, thereby demonstrating underdetermination in a model-theoretic sense. We conclude that relativity and quantum theory, in the model presented here, do not logically force eternalism, leaving ER as a viable alternative ontology.