Structural Realism

This paper argues that scientific realism commits us to a metaphysical determination relation between the mathematical entities that are indispensible to scientific explanation and the modal structure of the empirical phenomena those entities explain. The argument presupposes that scientific realism commits us to the indispensability argument. The viewpresented here is that the indispensability of mathematics commits us not only to the existence of mathematical structures and entities but to a metaphysical determination relation between those entities and the modal structure of (...) the physical world. The no-miracles argument is the primary motivation for scientific realism. It is a presupposition of this argument that unobservable entities are explanatory only when they determine the empirical phenomena they explain. I argue that mathematical entities should also be seen as explanatory only when they determine the empirical facts they explain, namely, the modal structure of the physical world. Thus, scientific realism commits us to a metaphysical determination relation between mathematics and physical modality that has not been previously recognized. The requirement to account for the metaphysical dependence of modal physical structure on mathematics limits the class of acceptable solutions to the applicability problem that are available to the scientific realist. (shrink)

In the pure powers ontology (PPO), basic physical properties have wholly dispositional essences. PPO has clear advantages over categoricalist ontologies, which suffer from familiar epistemological and metaphysical problems. However, opponents argue that because it contains no qualitative properties, PPO lacks the resources to individuate powers, and generates a regress. The challenge for those who take such arguments seriously is to introduce qualitative properties without reintroducing the problems that PPO was meant to solve. In this paper, I distinguish the core claim (...) of PPO: (i) basic physical properties have dispositional essences, from a hitherto unnoticed assumption: (ii) the dispositional essences of basic physical properties exclusively involve type-causal relations to other basic physical properties. I reject (ii), making room for a structuralist ontology in which all basic physical properties are pure powers, individuated by their places in a causal structure that includes not only other powers, but also physically realized qualitative properties such as shapes, patterns and structures. Such qualities individuate pure powers in the way that non-mental input and output properties individuate realized mental properties in functionalist theories of mind, except that here it is basic physical powers that are individuated by relations to realized non-powers. I distinguish one Platonic and two Aristotelian version of this theory, and argue that the Aristotelian versions require that grounding is not always a relative fundamentality relation, because the powers ground the qualities that individuate them. I argue that symmetric grounding is the best way to make sense of the relational individuation common to all structuralist ontologies, and is therefore no additional commitment of the one proposed here. (shrink)

This paper explores structuralism as a way to model theories from scientific practice. As a case study I analyzed a theory about the dynamics of the basal ganglia, a part of the brain that is involved in Parkinson's disease. After introducing the case study I explore how to structurally represent qualitative assumptions about disease, intervention and dynamical systems in general. I further explicate the structure of the basal ganglia theory in detail, how it explains Parkinson's disease and how it implies (...) treatments. I close with a consideration of how a structuralist representation could be useful in practice to explore and develop theories with the aid of a computer. (shrink)

The argument is directed at the view that scientific knowledge is just knowledge of the structure of the natural world and not knowledge of its intrinsic nature. The origin of the view is the post-Galilean conception of modern science, which views science as yielding a picture of nature stripped of all color, explaining all physical processes purely in terms of space-time, particles, fields, forces and the like, the intrinsic natures of which are never themselves analyzed. It is safe to say (...) that this conception of the limits of scientific knowledge, i.e. of its purely mathematical and structural character, is still a dominant one for both philosophers and scientists. (shrink)

James Ladyman and Don Ross, with David Spurrett and John Collier, Every Thing Must Go: Metaphysics Naturalized. Oxford University Press 2007 x+346 Philosophical Papers Vol. 37 2008: pp. 333-336.

In my review of Steven French's The structure of the world. Metaphysics & Representation. OUP, Oxford, 2014 I argue that the author is forced to navigate between the Scilla of Tegmark’s Pitagoreanism (2008) and the Carybdis of “blobobjectivism” (Horgan and Potrč 2008), namely the claim that the whole physical universe is a single concrete structurally complex but partless cosmos (a “blob”).

Within the standard structuralist approach, the theoretical description of a system by means of an empirical theory T is regarded as an extension process in which partial models are extended into models of T by supplementing suitable T-theoretical functions. Thereby, it is taken for granted that the base sets, on which these functions or relations are defined, can be assumed as given independently of the theory in question. My aim in this paper is to show that, in many cases, this (...) assumption is not justified. I will argue that this fact—which may be seen as a mere technical complication on first sight—turns out to have profound consequences for core concepts of the structuralist framework: First, the concept of intended applications has to be reconsidered. Second, the extension process has to be described in a more differentiated and complex way. Third, the theory-dependent determination of base sets has major implications concerning the defense mechanisms of empirical theories against conflicting observational data. (shrink)

We argue that the economy of nature constitutes an invocation of structure in the biological sciences, one largely missed by philosophers of biology despite the turn in recent years toward structural explanations throughout the philosophy of science. We trace a portion of the history of this concept, beginning with the theologically and economically grounded work of Linnaeus, moving through Darwin’s adaptation of the economy of nature and its reconstitution in genetic terms during the first decades of the Modern Synthesis. What (...) this historical case study reveals, we argue, is a window into the shifting landscape of the explanatory and ontic uses of structural concepts. In Linnaeus, the economy of nature has both ontic and explanatory import; in Darwin the ontic and explanatory aspects start to come apart ; and finally, in the Modern Synthesis, the economy of nature is replaced by the conceptual toolkit of population genetics, the structural elements of which are nearly entirely explanatory. Having traced a historical trajectory of structural concepts that moves from an ontic formulation to an increasingly explanatory one, we conclude by outlining some insights for structural realism. (shrink)

Le réalisme structural est une tentative d’établir un compromis entre le réalisme scientifique et l’empirisme, en restreignant le réalisme à la structure relationnelle des théories scientifiques. Il se décline en deux versions, épistémique et ontique. Le réalisme structural ontique propose de concevoir les relations nomologiques décrites par les théories comme des éléments primitifs de la réalité. Il est motivé, notamment, par le fait que sous sa forme épistémique, le réalisme structural ne se distingue pas réellement d’une position empiriste. Cependant, il (...) fait face à des difficultés, en particulier pour différencier relations physiques et mathématiques et rendre compte de l’ancrage expérimental des théories. Il est possible d’établir un parallèle entre ces difficultés et le problème de la mesure en mécanique quantique, qui concerne lui aussi les rapports entre modèle théorique et expérience : on constate alors qu’un réalisme structural épistémique est plus à même d’y répondre. Une solution de compromis entre le réalisme structural ontique et le réalisme structural épistémique pourrait permettre de conserver les avantages des deux positions. -/- Structural realism attempts to make a compromise between scientific realism and empiricism, by restricting our realist commitment to the relational structure of scientific theories. There are two main versions of the position: ontic, or epistemic. According to ontic structural realism, the nomological relations expressed by theories are the primitive entities of reality. This ontic version is motivated in particular by arguments to the effect that epistemic versions are not really distinct from mere empiricism. However according to some authors, it’s not clear that ontic structural realism can differentiate between physical and mathematical relations, and account for the relations between scientific theories and their experimental basis. These difficulties can be related to the measurement problem in quantum mechanics, which also concerns the link between theoretical models and experiments. It appears that epistemic structural realism is in a better position to respond to these difficulties. A compromise between both versions of structural realism could allow us to keep the advantages of both. (shrink)

Entrée encyclopédique / Encyclopedia Entry.

In this paper I discuss the Newman problem in the context of contemporary epistemic structural realism (ESR). I formulate Newman’s objection in terms that apply to today’s ESR and then evaluate a defence of ESR based on Carnap’s use of Ramsey sentences and Hilbert’s ε-operator. I show that this defence improves the situation by allowing a formal stipulation of non-structural constraints. However, it fails short of achieving object individuation in the context of satisfying the Ramsified form of a theory. Thus, (...) while limiting the scope of Newman’s argument, Carnap sentences do not fully solve the problem. (shrink)

We examine recent work in cognitive neuroscience that investigates brain networks. Brain networks are characterized by the ways in which brain regions are functionally and anatomically connected to one another. Cognitive neuroscientists use various noninvasive techniques (e.g., fMRI) to investigate these networks. They represent them formally as graphs. And they use various graph theoretic techniques to analyze them further. We distinguish between knowledge of the graph theoretic structure of such networks (structural knowledge) and knowledge of what instantiates that structure (nonstructural (...) knowledge). And we argue that this work provides structural knowledge of brain networks. We explore the significance of this conclusion for the scientific realism debate. We argue that our conclusion should not be understood as an instance of a global structural realist claim regarding the structure of the unobservable part of the world, but instead, as a local structural realist attitude towards brain networks in particular. And we argue that various local approaches to the realism debate, i.e., approaches that restrict realist commitments to particular theories and/or entities, are problematic insofar as they don't allow for the possibility of such a local structural realist attitude. (shrink)

When scientists put forward hypotheses, they sometimes involve new kinds of entities, which we can call 'hypothetical entities.' Hypothetical entities are pervasive in the sciences, and some examples include caloric and, up until very recently, the Higgs boson. Some hypothetical entities are discovered, as was the case with the Higgs boson, while scientists conclude that others, like caloric, do not exist. Hypothetical entities pose a number of important challenges for the philosophy of science, and my goal is to develop and (...) defend what I will call the suppositionalist view of hypothetical entities. In chapter 1, I examine the extant views of hypothetical entities, which I draw from the scientific realism debate. I argue that these views are all committed to the claim that terms for hypothetical entities putatively refer to empirical entities. In chapter 2, I develop the suppositionalist view of hypothetical entities. On this view, terms for hypothetical entities refer to what are called 'objects of supposition.' Examples of such objects from other domains include fictional characters like Superman and mathematical objects like the natural numbers. I draw from analogies with fiction and mathematics in order to develop the suppositionalist view in the scientific domain. In chapter 3, I give a history of a hypothetical entity that I will later use as a test case for views of hypothetical entities. In the late-eighteenth century, Antoine Lavoisier hypothesized that muriatic acid is composed of oxygen and a hypothetical entity called the 'muriatic radical.' In the early-nineteenth century, Humphry Davy's work on muriatic acid showed that it is actually composed of hydrogen and chlorine, and so muriatic acid is hydrochloric acid. Finally, in chapter 4, I use the history of the muriatic radical in order to argue against the extant views, and for the suppositionalist view. I argue that the former are committed to giving a history of the muriatic radical that is either whiggish or incomplete. The latter, however, can give us a non-whiggish history that is more complete, and hence it is preferable to the extant views. (shrink)

In the debate of scientific realism, the argument from underdetermination of theories by evidence is put forward by the anti-realist side. According to this argument, for any scientific theory rival theories can be found which are equally well supported by the evidence but incompatible with the original theory. Structural realism is a form of realism that limits the realistic belief in the existence of the entities and structures talked about in scientific theories: Only the structures of reality are relevant in (...) an epistemic sense and responsible for the truth and falsehood of theories. In the light of the antirealistic arguments, structural realism is supposed to have clear advantages over other varieties of scientific realism. In particular, Worrall ([21]) argues that structural realism is immune against the argument from underdetermination. I will sketch Worrall’s line of argument in a more systematic manner and conclude that it is based on some problematic preconditions. (shrink)

Fundamental physics contains an important link between properties of elementary particles and continuous symmetries of particle systems. For example, properties such as mass and spin are said to be 'associated' with specific continuous symmetries. -/- These 'associations' have played a key role in the discovery of various new particle kinds, but more importantly: they are thought to provide a deep insight into the nature of physical reality. The link between properties and symmetries has been said to call for a radical (...) revision of perceived metaphysical orthodoxy. However, if we are to use claims about an 'association' between properties and symmetries in the articulation of metaphysical views, we first need to develop a sufficiently precise understanding of the content of these claims. The goal of this paper is to do just that. (shrink)

Any successful account of the metaphysics of mechanistic causation must satisfy at least five key desiderata. In this paper, I lay out these five desiderata and explain why existing accounts of the metaphysics of mechanistic causation fail to satisfy them. I then present an alternative account which does satisfy the five desiderata. According to this alternative account, we must resort to a type of ontological entity that is new to metaphysics, but not to science: constraints. In this paper, I explain (...) how a constraints-based metaphysics fits best with the emerging consensus on the nature of mechanistic explanation. (shrink)

The main purpose of this paper is to test structural realism against (one example from) the historical record. I begin by laying out an existing challenge to structural realism -- that of providing an example of a theory exhibiting successful structures that were abandoned -- and show that this challenge can be met by the miasma theory of disease. However, rather than concluding that this is an outright counterexample to structural realism, I use this case to show why it is (...) that structural realism, in its current form, has trouble dealing with theories outside physics. I end by making some concrete suggestions for structural realists to pursue if, indeed, they are serious about extending structural realism to other domains. (shrink)

The intuition of the naı¨ve realist, miracle arguments notwithstanding, is countered forcefully by a host of considerations, including the possibility of underdetermination, and criticisms of abductive inferences to explanatory hypotheses. Some have suggested that an induction may be performed, from the perspective of present theories, on their predecessors. Past theories are thought to be false, strictly speaking; it is thus likely that present-day theories are also false, and will be taken as such at an appropriate future time.

Howard argues that the existence of unitarily inequivalent representations in Quantum Field Theory presents a problem for structural realism in this context. I consider two potential ways round this problem: 1), follow Wallace in adopting the 'naive' Lagrangian form of QFT with cut-offs; 2), adapt Ruetsche's 'Swiss Army Knife' approach. The first takes us into the current debate between Wallace and Fraser on conventional vs. algebraic QFT. The second involves consideration of the role of inequivalent representations in understanding spontaneous symmetry (...) breaking and quantum statistics. In both cases, I suggest, the structural realist has sufficient room to manoeuvre. (shrink)

Although scientific realism is the default position in the life sciences, philosophical accounts of realism are geared towards physics and run into trouble when applied to fields such as biology or neuroscience. In this paper, I formulate a new robustness-based version of entity realism, and show that it provides a plausible account of realism for the life sciences that is also continuous with scientific practice. It is based on the idea that if there are several independent ways of measuring, detecting (...) or deriving something, then we are justified in believing that it is real. I also consider several possible objections to robustness-based entity realism, discuss its relationship to ontic structural realism, and show how it has the potential to provide a novel response to the pessimistic induction argument. (shrink)

In the 20th century the infiltration of scientific elements into philosophical currents not only reached its maximum, but also science itself became a "philosophical factor". We look at these processes in physics starting from the fall of mechanistic philosophy. The advent of relativity theory and quantum mechanics has changed physics as science and raised a host of philosophical questions. Traditionally philosophical questions concerning space, time and causality cannot be any longer considered with no help of these theories. Relativistic cosmology and (...) its observational successes in the last decades of the century, for the first time in the history of human thought, provided a global framework for both science and philosophy. And the current search for the final unifying theory of physics leads directly to the most foundational questions of an ontological character. We argue that the success of the 20th century physics strongly suggests a kind of structuralist ontology. /// No século XX, a infiltração de elementos científicos nas correntes filosóficas não só alcançou o seu máximo, mas também é verdade que a própria ciência se tornou um "factor filosófico". O presente artigo considera estes processos na física, a começar com a decadência da filosofia mecanicista. O advento da teoria da relatividade e da mecânica quântica transformou a física enquanto ciência e levantou uma plêiade de questões filosóficas. Questões tradicionais acerca do espaço, do tempo e da causalidade não podem mais ser consideradas sem o contributo destas teorias. A cosmologia relati-vista e os seus sucessos observacionais nas últimas décadas do século passado, e isso pela primeira vez na história do pensamento humano, fornecem um esquema global tanto para a ciência como para a filosofia. Além disso, a busca corrente de uma última teoria unificadora da física conduz directamente às questões mais fundacionais de carácter ontológico. O autor do artigo defende que os sucessos da física do século XX sugerem fortemente uma espécie de ontologia estruturalista. (shrink)

Ontic structural realism (OSR) claims that all there is to the world is structure. But how can this slogan be turned into a worked-out metaphysics? Here I consider one potential answer: a metaphysical framework known as generalism (Dasgupta, 2009, 2016). According to the generalist, the most fundamental description of the world is not given in terms of individuals bearing properties, but rather, general facts about which states of affairs obtain. However, I contend that despite several apparent similarities between the positions, (...) generalism is unable to capture the two main motivations for OSR. I suggest instead that OSR should be construed as a meta-metaphysical position. (shrink)

In this paper I elicit a prediction from structural realism and compare it, not to a historical case, but to a contemporary scientific theory. If structural realism is correct, then we should expect physics to develop theories that fail to provide an ontology of the sort sought by traditional realists. If structure alone is responsible for instrumental success, we should expect surplus ontology to be eliminated. Quantum field theory (QFT) provides the framework for some of the best confirmed theories in (...) science, but debates over its ontology are vexed. Rather than taking a stand on these matters, the structural realist can embrace QFT as an example of just the kind of theory SR should lead us to expect. Yet, it is not clear that QFT meets the structuralist's positive expectation by providing a structure for the world. In particular, the problem of unitarily inequivalent representations threatens to undermine the possibility of QFT providing a unique structure for the world. In response to this problem, I suggest that the structuralist should endorse pluralism about structure. (shrink)

The ways in which space-time points and elementary particles are modeled share a curious feature: neither seems to specify which basic object has which properties. This chapter sketches the motivation for this claim and searches for an explanation for it. After reviewing several proposals, it argues for a view according to which objects occupy their place in a given relational structure essentially. This view, which is termed minimal structural essentialism, provides a metaphysical grounding for the physical equivalence of models related (...) by permutation. An interesting consequence of this position is that space-time points and elemental particles turn out to be individuals, albeit of a rather different sort than has traditionally been considered. (shrink)

Structural realists claim that we should endorse only what our scientific theories say about the structure of the unobservable world. But according to Newman’s Objection, the structural realist’s claims about unobservables are trivially true. In recent years, several theorists have offered responses to Newman’s Objection. But a common complaint is that these responses “give up the spirit” of the structural realist position. In this paper, I will argue that the simplest way to respond to Newman’s Objection is to return to (...) one of the standard motivations for adopting structural realism in the first place: the No Miracles Argument. Far from betraying the spirit of structural realism, the solution I present is available to any theorist who endorses this argument. (shrink)

We set out a fundamental ontology of atomism in terms of matter points. While being most parsimonious, this ontology is able to match both classical and quantum mechanics, and it remains a viable option for any future theory of cosmology that goes beyond current quantum physics. The matter points are structurally individuated: all there is to them are the spatial relations in which they stand; neither a commitment to intrinsic properties nor to an absolute space is required. The spatial relations (...) change. All that is needed to capture change is a dynamical structure, namely dynamical relations as expressed in terms of the dynamical parameters of a physical theory. (shrink)

In the present paper the attempt is made for the first time to formalize the modern theory of elementary particles based on the structuralist approach. To this end, the description within the scope of the so-called standard model is considered. In the physics of elementary particles the term ‘standard model’ denotes the summary of theories which describe the various elementary building blocks of matter as well as their interactions between each other. This model represents one of the most successful theories (...) in physics, particularly because of the impressive experimental confirmation. Hence a structuralist reconstruction of it is a challenging task. (shrink)

Ladyman and Ross argue that quantum objects are not individuals and use this idea to ground their metaphysical view, ontic structural realism, according to which relational structures are primary to things. LR acknowledge that there is a version of quantum theory, namely the Bohm theory, according to which particles do have denite trajectories at all times. However, LR interpret the research by Brown et al. as implying that "raw stuff" or haecceities are needed for the individuality of particles of BT, (...) and LR dismiss this as idle metaphysics. In this paper we note that Brown et al.'s research does not imply that haecceities are needed. Thus BT remains as a genuine option for those who seek to understand quantum particles as individuals. However, we go on to discuss some problems with BT which led Bohm and Hiley to modify it. This modified version underlines that, due to features such as context-dependence and non-locality, Bohmian particles have a very limited autonomy in situations where quantum effects are non-negligible. So while BT restores the possibility of quantum individuals, it also underlines the primacy of the whole over the autonomy of the parts. The later sections of the paper also examine the Bohm theory in the general mathematical context of symplectic geometry. This provides yet another way of understanding the subtle, holistic and dynamic nature of Bohmian individuals. We finally briefly consider Bohm's other main line of research, the "implicate order", which is in some ways similar to LR's structural realism. (shrink)

Cartesian arguments for global skepticism about the external world start from the premise that we cannot know that we are not in a Cartesian scenario such as an evil-demon scenario, and infer that because most of our empirical beliefs are false in such a scenario, these beliefs do not constitute knowledge. Veridicalist responses to global skepticism respond that arguments fail because in Cartesian scenarios, many or most of our empirical beliefs are true. Some veridicalist responses have been motivated using verificationism, (...) externalism, and coherentism. I argue that a more powerful veridicalist response to global skepticism can be motivated by structuralism, on which physical entities are understood as those that play a certain structural role. I develop the structuralist response and address objections. (shrink)

The Metaphysics of Relations is an anthology of thirteen original papers plus an introduction, addressing the philosophical issue of relations from a contemporary and historical perspective. The result is a remarkably coherent whole, where the different papers shed light on each other even though very few of them explicitly address interconnections. As a consequence, the book works really well as an introduction to the philosophical issue on relations, while the individual papers represent cutting edge research on the particular issues that (...) they focus on. The mix of contemporary and historical perspectives means you get a snapshot view of the contemporary issues, as well as insights into their historical development. (shrink)

In this paper I challenge and adjudicate between the two positions that have come to prominence in the scientific realism debate: deployment realism and structural realism. I discuss a set of cases from the history of celestial mechanics, including some of the most important successes in the history of science. To the surprise of the deployment realist, these are novel predictive successes toward which theoretical constituents that are now seen to be patently false were genuinely deployed. Exploring the implications for (...) structural realism, I show that the need to accommodate these cases forces our notion of “structure” toward a dramatic depletion of logical content, threatening to render it explanatorily vacuous: the better structuralism fares against these historical examples, in terms of retention, the worse it fares in content and explanatory strength. I conclude by considering recent restrictions that serve to make “structure” more specific. I show however that these refinements will not suffice: the better structuralism fares in specificity and explanatory strength, the worse it fares against history. In light of these case studies, both deployment realism and structural realism are significantly threatened by the very historical challenge they were introduced to answer. (shrink)

I deploy a scientific metaphysical argument for scientific realism that is both inspired by and reinforces Ian Hackings corroboration argument for scientific realism by using information theory. Ill then present an original support for that argument in more systematic (although not formal) statistical terms, deploying an adaptation of the Kullback-Leibler divergence for the purpose. Information theory, correctly applied, reveals that the relevant part of the structure of data for making scientific inferences is independent of epistemic and conceptual inputs. Theory-orientated arguments (...) against scientific realism based upon the inseparability of measured data, theory, and other epistemic components fail on contingent information theoretic grounds. -/- Information Theoretic Support for Hacking's Corroboration Argument. Available from: https://www.researchgate.net/publication/309728366_Information_Theoretic_Support_for_Hacking%27s_Cor roboration_Argument [accessed Jul 5, 2017]. (shrink)

In this paper, a new account of empirical claims in structuralism is developed. Its novelty derives from the use that is made of the linguistic approach to scientific theories despite the presumed incompatibility of structuralism with that approach. It is shown how the linguistic approach can be applied to the framework of structuralism if the semantic foundations of that approach are refined to do justice to the doctrine of indirect interpretation of theoretical terms. This doctrine goes back to Carnap but (...) has been advanced until the present day without a proper semantic explanation. (shrink)

Ontic structural realism is at its core the view that “structure is ontologically fundamental.” Informed from its inception by the scientific revolutions that punctuated the 20th century, its advocates often present the position as the perspective on ontology best befitting of modern physics. But the idea that structure is fundamental has proved difficult to articulate adequately, and what OSR's claimed naturalistic credentials consist in is hard to precisify as well. Nor is it clear that the position is actually supported by (...) our most fundamental physical theories. What is clear, however, is that structuralists have revealed a seam of material at the core of modern physics that is replete with implications for metaphysics. This article will survey some positions subsumed under the rubric of OSR, considering both their warrant and the interconnections that exist between them. It will be argued that the fundamental kind properties pose a challenge to ontic structuralism, because it seems that these properties do not supervene upon the relevant structures. But it will also be argued that the development of structuralist metaphysics will require both an engagement with the details of modern physical theories and the deployment of tools more typically developed in a priori metaphysics. As such, it seems armchair metaphysicians have not just a stake in whether OSR's claims may ultimately be shown to stand up, but a crucial role to play in getting them to the point where they can be subjected to scrutiny in the first place. (shrink)

There are two ways of reading Newman’s objection to Russell’s structuralism. One assumes that according to Russell, our knowledge of a theory about the external world is captured by an existential generalization on all non-logical symbols of the theory. Under this reading, our knowledge amounts to a cardinality claim. Another reading assumes that our knowledge singles out a structure in Russell’s (and Newman’s) sense: a model theoretic structure that is determined up to isomorphism. Under this reading, our knowledge is far (...) from trivial, for it amounts to knowledge of the structure of the relations between objects, but not their identity. Newman’s objection is then but an expression of structural realism. Since therefore the content of theories is described by classes of structures closed under isomorphism, the most natural description of a theory in structural realism is syntactic. (shrink)

What ontology does realism about the quantum state suggest? The main extant view in contemporary philosophy of physics is wave-function realism . We elaborate the sense in which wave-function realism does provide an ontological picture, and defend it from certain objections that have been raised against it. However, there are good reasons to be dissatisfied with wave-function realism, as we go on to elaborate. This motivates the development of an opposing picture: what we call spacetime state realism , a view (...) which takes the states associated to spacetime regions as fundamental. This approach enjoys a number of beneficial features, although, unlike wave-function realism, it involves non-separability at the level of fundamental ontology. We investigate the pros and cons of this non-separability, arguing that it is a quite acceptable feature, even one which proves fruitful in the context of relativistic covariance. A companion paper discusses the prospects for combining a spacetime-based ontology with separability, along lines suggested by Deutsch and Hayden. (shrink)