William Simpson

We propose an extension of Bell-type Bohmian quantum field theories, called Contextual Bohmian Quantum Field Theory (CBQFT), which integrates micro-level dynamics and macro-level contextual structure within a unified, ontologically explicit formalism. CBQFT introduces classical variables $$\Lambda$$ that encode macroscopic contexts—such as detector configurations, thermal phases, or symmetry-breaking sectors—and allows these to modulate the underlying quantum dynamics in a lawlike way. We develop two versions of the model. CBQFT-1 treats context as a fixed but dynamically influential background, entering via a context-sensitive Hamiltonian and modified Bell-type jump rates on a single Fock space. CBQFT-2 upgrades context to a dynamical variable co-evolving with the particle (or field) configuration: $$\Lambda (x,t)$$ selects a (typically inequivalent) representation of the field algebra on a Hilbert space, wavefunctions are realised as global sections of the resulting Hilbert bundle, and Bohmian trajectories are guided by globally well-defined velocity fields constructed from local currents. Context transitions in CBQFT-2 are governed by a stochastic kernel informed by particle (or field) configurations and histories. This yields a Bohmian QFT with an explicit feedback loop between quantum events and macroscopic structure, offering a hylomorphic account of measurement, decoherence, and top–down causation.

Primitive ontology (PO) approaches to quantum theory aim to describe the world in terms of matter distributed in 3-space (the PO). David Albert argues they cannot recover macroscopic structure without ad hoc coarse-graining (“squinting”). This paper formalises a Macro-Object Problem for the PO-approach based on Albert’s critique and enlists Contextual Bohmian Mechanics (CBM) to offer a solution. CBM augments the PO with a local context field $$\Lambda (x,t)$$. While $$\Lambda$$ is fixed, the wavefunction $$\Psi$$ evolves unitarily and the particles _Q_ follow a Bohmian guidance law; when $$\Lambda$$ changes on a bounded region _R_, a local completely positive instrument updates the state, with open-system energy bookkeeping and statistical locality outside _R_. I show that $$\Lambda$$ tiles spacetime into macro-object tokens, modulates the dynamics to confer genuine causal powers, and does so entirely within 3-space—thereby satisfying all the conditions for solving the Macro-Object Problem. I argue that physical objects are hylomorphic composites of _both_ matter (hylē) _and_ form (morphē), with matter corresponding to the particles and $$\Lambda$$ serving as a rigorous surrogate for local form.

This paper responds to Halvorson’s reflections on hylomorphism by addressing its quantum application (Koons and Simpson) and contextually emergent physics (Ellis and Drossel). It also critiques physicalist interpretations of quantum mechanics and argues for the fundamental nature of thermodynamic phenomena. Koons, Simpson, Ellis and Drossel defend hylomorphism as a framework that challenges dogmatic semi-physicalism. They examine causal pluralism, semantic indeterminacy and the limited validity of quantum mechanics, emphasising the role of micro and macroscopic elements in shaping a consistent worldview.

This special issue explores both the metaphysical and theological significance of “middle-sized things” — everyday objects, persons, and sacraments — in light of developments in contemporary science and philosophy. Against prevailing neo-Humean and microphysicalist backdrops, where only microphysical entities are taken as fundamental, contributors interrogate the ontological reality and causal powers of the macroscopic domain through engagements with quantum physics, biology, the metaphysics of substance, and sacramental theology. Essays range from arguments for Aristotelian hylomorphism and critiques of reductionism to narrative theories of identity and teleological accounts of divine action. Together, they examine whether middle-sized entities can be causally efficacious, metaphysically basic, and theologically significant.

This article surveys recent work on primitive ontology (PO) approaches to quantum mechanics, focusing on proposals that seek to integrate this approach with the metaphysics of causal powers. PO approaches aim to provide a clear metaphysical picture in which the world consists of local entities such as particles, matter density fields or flashes, and these entities compose macroscopic objects, such as scientists and their measuring devices. To account for the behaviour of these local entities, some PO theories invoke the metaphysics of powers. After motivating PO approaches and contrasting them with wave function realism, I consider the development of power‐based POs, contrasting them with both Humean POs and POs which invoke primitive laws. I explain how different power‐based frameworks address key quantum phenomena, and I survey some difficulties, including the Problem of Holism, of small worlds and of top‐down causation. Such challenges are best confronted, I suggest, by drawing on Aristotelian hylomorphism: If powers are grounded in forms that unify physical systems, then power‐based POs can accommodate holistic and context‐sensitive behaviour.

This Element introduces Aristotle's doctrine of hylomorphism, which provides an account of substances in terms of their 'matter' and 'form', adapting and applying it to the interface between physics and biology. It begins by indicating some reasons for the current revival of hylomorphism and by suggesting a way of classifying the confusing array of hylomorphisms that have arisen. It argues that, in order for composite entities to have irreducible causal powers which make a difference to how nature unfolds, they must have substantial forms which transform their matter such that the powers of their physical parts are grounded in the composite entity as a whole. It suggests how a contemporary form of hylomorphism might contribute to the philosophy of biology by grounding the non-intentional form of teleology that features in the identity conditions of biological systems, affirming a real distinction between living organisms and heaps of matter. This title is also available as Open Access on Cambridge Core.

This book explores the relationship between a scientifically updated Aristotelian philosophy of nature and a scientifically engaged theology of nature that cuts across interdisciplinary boundaries. It features original contributions by some of the best scholars engaging with Aristotelianism in contemporary metaphysics, philosophy of science, and philosophical theology. Despite the growing interest in Aristotelian approaches to contemporary philosophy of science, few metaphysicians have engaged directly with the question of how a neo-Aristotelian metaphysics of nature might change the landscape for theological discussion concerning theology and naturalism, the place of human beings within nature, or the problem of divine causality. The chapters in this volume are collected into three thematic sections: Naturalism and Nature, Mind and Nature, and God and Nature. By pushing the current boundaries of neo-Aristotelian metaphysics to recover the traditional notion of substantial forms in physics, reframe the principle of proportionality in biology, and restore the hierarchy of being familiar to ancient philosophy, this book advances a metaphysically unified framework that accommodates both scientific and theological knowledge, enriching the interaction between science, philosophy and theology. Neo-Aristotelian Metaphysics and the Theology of Nature will be of interest to scholars and advanced students working in metaphysics, philosophy of science, natural theology, philosophical theology, and analytic theology.

I outline a hylomorphic account of physical reality in which the cosmos as a whole has mental properties which explain its nomological order. According to this theory, the cosmos is directed in its temporal development toward certain ends or goals which it intends, and these ends are immanent to the cosmos rather than being imposed upon it. My object in doing so is to argue that, contrary to Sean Carroll (2021), a view of physical reality as having intrinsically mental aspects need not induce any modifications of the known laws of physics nor violate 'causal closure' under physical laws. Rather, this soft form of naturalism, which includes final causes within nature, provides a foundation for the laws of physics that is lacking in Carroll's hard form of naturalism, which excludes mind from fundamental reality. I propose a trilemma for Carroll in which he should either: abandon naturalism, by admitting that the laws of physics are imposed by a divine mind; abandon realism, by conceding that 'laws' are constructed by human minds; or embrace cosmopsychism, by acknowledging that the cosmos as a whole instantiates a mind. I argue that cosmic hylomorphism, which links consciousness with intentional cognition, is preferable to non-hylomorphic versions of cosmopsychism, which tend to prioritize consciousness over intentionality.

Medieval interpretations of hylomorphism, in which substances are conceived as metaphysical composites of prime matter and substantial form, are receiving attention in contemporary philosophy. It has even been suggested that a recovery of Aquinas's conception of prime matter as a ‘pure potentiality’, lacking any actuality apart from substantial form, may be expedient in hylomorphic interpretations of quantum mechanics. In this paper, we consider a recent hylomorphic interpretation of non-relativistic quantum mechanics, the theory of Cosmic Hylomorphism, which does not explicitly invoke any notion of prime matter in its original formulation. We argue that prime matter does in fact play a role in constituting and individuating particles in this theory. However, we demonstrate that the notion of prime matter which features in the extended version of Cosmic Hylomorphism that we propose here is distinct from Aquinas's conception of prime matter, inasmuch as it has discrete metaphysical parts.

Medieval interpretations of hylomorphism, in which substances are conceived as metaphysical composites of prime matter and substantial form, are receiving attention in contemporary philosophy. It has even been suggested that a recovery of Aquinas's conception of prime matter as a ‘pure potentiality’, lacking any actuality apart from substantial form, may be expedient in hylomorphic interpretations of quantum mechanics. In this paper, we consider a recent hylomorphic interpretation of non-relativistic quantum mechanics, the theory of Cosmic Hylomorphism, which does not explicitly invoke any notion of prime matter in its original formulation. We argue that prime matter does in fact play a role in constituting and individuating particles in this theory. However, we demonstrate that the notion of prime matter which features in the extended version of Cosmic Hylomorphism that we propose here is distinct from Aquinas's conception of prime matter, inasmuch as it has discrete metaphysical parts.

The wave function of quantum mechanics can be understood in terms of the dispositional role it plays in the dynamics of a distribution of matter in three-dimensional space (or four-dimensional spacetime). There is more than one way, however, of specifying its dispositional role. This paper considers Suárez’s theory of ‘Bohmian dispositionalism’, in which the particles are endowed with their own ‘Bohmian dispositions’, and Simpson’s theory of ‘Cosmic Hylomorphism’, in which the particle configuration comprises a hylomorphic substance which has an intrinsic power. I argue that Bohmian dispositionalism fails to capture intuitively correct counterfactuals about what would happen in Small Worlds which have only a small number of particles, but that this problem is avoided by Cosmic Hylomorphism, in which the cosmic power manifests a teleological process.

Esfeld has proposed a minimalist ontology of nature called ‘super-Humeanism’ that purports to accommodate quantum phenomena and avoid standard objections to neo-Humean metaphysics. I argue that Esfeld’s sparse ontology has counterintuitive consequences and generates two self-undermining dilemmas concerning the nature of time and space. Contrary to Esfeld, I deny that super-Humeanism supports an ontology of microscopic particles that follow continuous trajectories through space. 1Introduction 2Matter without Physical Properties 2.1The primitive ontology approach 2.2Super-Humean matter points 3Objections to Super-Humeanism 3.1Symmetric worlds 3.2Temporal dilemma 3.3Persistence problem 4Conclusion.

Toby Handfield has advanced a subtle form of dispositionalism that purports to reconcile the concept of causal powers with broadly Humean convictions by dissolving the requirement for objectively modal relations between powers and their manifestations. He suggests we should identify manifestations with certain types of causal processes, and identify powers with properties that are parts of their structures. The modal features of causal powers can then be explained in terms of internal relations between a power and the property of being a certain type of causal process, but these relations are supervenient and do not add anything to the basic ontology. In this way, causal powers may be ‘connected’ to their manifestations without admitting objectively modal relations. I disagree with this characterisation of causal powers and its identification of manifestations with types of causal processes: I question the assumption that causal processes can be isolated in quantum physics in the way Handfield requires and confront Humean dispositionalism with the problem of individuating powers in an entangled world.

In this chapter, I argue that Aristotle’s doctrine of hylomorphism, which conceived the natural world as consisting of substances which are metaphysically composed of matter and form, is ripe for rehabilitation in the light of quantum physics. I begin by discussing Aristotle’s conception of matter and form, as it was understood by Aquinas, and how Aristotle’s doctrine of hylomorphism was ‘physicalised’ and eventually abandoned with the rise of microphysicalism. I argue that the phenomenon of quantum entanglement, and the emergence of irreducibly macroscopic phenomena in finite temperature quantum systems, have given us good reasons to doubt the truth of microphysicalism. In support of my argument, I show how to construct a hylomorphic interpretation of the de Broglie-Bohm theory that posits a single Cosmic Substance. I then show how to construct a hylomorphic interpretation of an alternative ‘contextual’ wave function collapse theory (recently proposed by the physicists Barbara Drossel and George Ellis) which posits a plurality of thermal substances. Both of these neo-Aristotelian ontologies reject the microphysicalist dogma that nature consists solely of some set of microscopic constituents.

In this paper, we challenge a wide-spread assumption among philosophers that contemporary physics supports physical state monism. This is the claim that the causal powers of a system supervene upon the ‘lower-level’ laws and the lower-level state of the cosmos (as represented by our ‘best physics’). On this view, it makes sense to ignore a macroscopic system’s higher-level properties in determining its causal powers, since any higher-level powers are merely artifacts of our special interests. We argue that this assumption is common both to microphysicalism, which carves the cosmos into a set of microscopic constituents, and priority monism, which posits a single cosmic substance, but is incompatible with any form of physical pluralism that attributes irreducibly higher-level powers to entities of intermediate scales. We consider a number of case studies in contemporary physics which fail to support the thesis of state monism. We argue that the causal powers of many systems are (determined by) higher-level, macroscopic properties that are neither reducible nor weakly emergent, and that contemporary physics is compatible with some kind of pluralism that affirms that these entities are robustly real. A pluralist ontology is likely to have implications for discussions of free will and agency.

The primitive ontology approach to quantum mechanics seeks to account for quantum phenomena in terms of a distribution of matter in three-dimensional space and a law of nature that describes its temporal development. This approach to explaining quantum phenomena is compatible with either a Humean or powerist account of laws. In this paper, I offer a powerist ontology in which the law is specified by Bohmian mechanics for a global configuration of particles. Unlike in other powerist ontologies, however, this law is not grounded in a structural power that is instantiated by the global configuration. Instead, I combine the primitive ontology approach with Aristotle’s doctrine of hylomorphism to create a new metaphysical model, in which the cosmos is a hylomorphic substance with an intrinsic power to choreograph the trajectories of the particles.

Despite the growing interest in Aristotelian approaches to contemporary philosophy of science, few metaphysicians have engaged directly with the question of how a neo-Aristotelian metaphysics of nature might change the landscape for theological discussion concerning theology and naturalism, the place of human beings within nature, or the problem of divine causality. The chapters in this volume are collected into three thematic sections: Naturalism and Nature, Mind and Nature, and God and Nature. By pushing the current boundaries of neo-Aristotelian metaphysics to recover the traditional notion of substantial forms in physics, reframe the principle of proportionality in biology, and restore the hierarchy of being familiar to ancient philosophy, this book advances a metaphysically unified framework that accommodates both scientific and theological knowledge, enriching the interaction between science, philosophy and theology. Neo-Aristotelian Metaphysics and the Theology of Nature will be of interest to scholars and advanced students working in metaphysics, philosophy of science, natural theology, philosophical theology, and analytic theology.

The last two decades have seen two significant trends emerging within the philosophy of science: the rapid development and focus on the philosophy of the specialised sciences, and a resurgence of Aristotelian metaphysics, much of which is concerned with the possibility of emergence, as well as the ontological status and indispensability of dispositions and powers in science. Despite these recent trends, few Aristotelian metaphysicians have engaged directly with the philosophy of the specialised sciences. Additionally, the relationship between fundamental Aristotelian concepts—such as "hylomorphism", "substance", and "faculties"—and contemporary science has yet to receive a critical and systematic treatment. _Neo-Aristotelian Perspectives on Contemporary Science _aims to fill this gap in the literature by bringing together essays on the relationship between Aristotelianism and science that cut across interdisciplinary boundaries. The chapters in this volume are divided into two main sections covering the philosophy of physics and the philosophy of the life sciences. Featuring original contributions from distinguished and early-career scholars, this book will be of interest to specialists in analytical metaphysics and the philosophy of science.