The Dependence of Objects on Structure: Tailoring our Metaphysics to Fit the Physics

1. The Dependence of Objects on Structure: Tailoring our Metaphysics to Fit the Physics Steven French Dept. of Philosophy University of Leeds

2. Acknowledgments • Thanks to Jos and Richard for organising such a congenial workshop and to the Lorentz Centre for funding, facilities, food …. • Thanks also to James Ladyman, Angelo Cei, Terry Horgan, Kerry McKenzie, Laurie Paul, David Wallace and all… for helpful discussions.

3. Part, Whole and Composition • General Composition Question: What iscomposition? • Special Composition Question In which cases is it true of certain objects that they compose something? • Inverse Composition Question In which cases is it true of an object that there are objects that compose it? (P. Inwagen, Material Beings, Ithaca NY: Cornell University Press, 1990, pp. 39-48 )

4. Part, Whole and Composition: Double Standards • Double Standards • answer to GCQ (but not SCQ or ICQ) must be a conceptual truth • e.g. xscompose yiff no two of the xs occupy overlapping regions of space and y occupies the sum of the regions of space occupied by the xs. • fails because counter-example is conceivable • why adopt such ‘high’ standards? (K. Hawley, ‘Principles of Composition and Criteria of Identity’, Australasian Journal of Philosophy, 84.4 (2006), 481-93) • revelatory of problems with metaphysics? • cf. Hacking: ‘bland’ metaphysical assertion not enough (Hacking, I. (1975), ‘The Identity of Indiscernibles’,Journal of Philosophy, 72, pp. 249-256)

5. Part, Whole and Composition: Two Desiderata • Two Desiderata (T. Horgan and M. Potrc, Austere Realism, MIT Press 2008, p. 18) • Unitary answers • answers to the above questions should be general and systematic • Mesh with common sense and/or physics • answers should yield an ontology that conforms reasonably well to pre-theoretic and scientific beliefs • Unitarity trumps Meshing • further problem for metaphysics?

6. Part, Whole and Composition: Double Standards and Unitarity • Double standards and unitary answers: • Hawley: cf criteria of identity • just as criteria of identity can differ for different kinds of thing, so can answers to the GCQ • Ladyman and Ross (Everything Must Go, OUP 2007, p.21) • different scientific domains, different composition relations

7. Part, Whole and Composition: Double Standards and Unitarity ‘It [the general composition relation] is supposed to be the relation that holds between the parts of any whole but the wholes mentioned above are hugely disparate and the composition relations studied by the special sciences are sui generis. We have no reason to believe that an abstract composition relation is anything other than an entrenched philosophical fetish.’ (L&R p. 21)

8. Part, Whole and Composition • Meshing • Satisfy naturalist tendencies (cfLadyman and Ross’s PNC) • Problem: underdetermination of metaphysics by physics • e.g. identity and QM (S.French & D. Krause, Identity in Physics, OUP 2006) • Example of ‘metaphysical humility’ • extensive array of metaphysical ‘facts’ about which we can have no knowledge • Response: be less humble • rule out such ‘facts’ (esp. those problematic for realist)

9. (Modest but Not So Humble) Structuralism • Shift in ontological focus • objects  structures (see S. French and J. Ladyman, ‘In Defence of Ontic Structural Realism’, forthcoming in A. Bokulich and P. Bokulich, Scientific Structuralism, Boston Studies in the Philosophy of Science; Springer) • Physics and Philosophy in the 20th C. • Duhem, Poincaré, Cassirer, Russell, Eddington, Born … • reconceptualisation of physical objects via structure • characterisation of structure via group theory (objectivity)

10. Two Forms • ESR: All that we know is structure • Agnosticism about ‘objects’  humility • (J. Worrall, 'Structural Realism: The Best of Both Worlds?', Dialectica43 (1989) pp. 99-124) • OSR: All that there is, is structure • (J. Ladyman, 'What is Structural Realism?', Studies in History and Philosophy of Science, 29 (1998) pp. 409-24; S. French, ‘Structure as a Weapon of the Realist’, Proceedings of the Aristotelian Society 106 (2006) pp. 170-187. J. Ladyman et. al., Everything Must Go, OUP 2007)

11. Two Variants • Eliminativist OSR • structure, no objects • French, Ladyman • Non-Eliminativist OSR • structure + ‘thin’ objects • identity given contextually • e.g. relationally via ‘weak discernibility’ (fermions; bosons contentious) • Ladyman, Saunders (Muller, F., and M. Seevinck (2009), “Discerning Elementary Particles”, Philosophy of Science 76: 179–200.; Ladyman, J. and  Bigaj, T. (2010), ‘The Principle of the Identity of Indiscernibles and Quantum Mechanics’, Philosophy of Science 77: 117–136)

12. Issues • What is structure? • What is the relationship between structure and (putative) objects?

13. What is structure: laws and symmetry • Structuralist methodology: • theoriespresent laws, symmetries … • laws: relations between properties • identity of properties given by nomic role • resist further step of positing (metaphysically robust) • objects • putative objects (eg particles) reconceptualised and • characterised via symmetry groups • (E. Castellani, 'Quantum Mechanics, Objects and Objectivity', in C. Garola and • A. Rossi, The Foundations of Quantum Mechanics – Historical Analysis and • Open Questions, pp. 105-114, Kluwer, 1993)

14. What is structure: laws and symmetry • Objects (metaphysically) dependent on structures • (role of symmetries)‏ • Properties (metaphysically) dependent on laws • (inc. conservation laws) • Structure (putative) objects and properties • ‘Top down’ metaphysics rather than ‘bottom up’ • (see A. Cei and S. French, ‘Getting Away from Governance: • A Structuralist Approach to Laws and Symmetries’)

15. What is the relationship between structure and objects: tables and particles • Eddington and his two tables • Stebbing: object of scientific description ≠ ‘table’ • Thomasson: ‘… scientific theories … do not use sortals such as ‘table’, and if science and common sense are using sortals of different categories, the ‘things’ picked out by the two descriptions cannot be identical.’ (A. Thomasson, Ordinary Objects, OUP 2997, p. 142) No conflictinflationary ontology

16. What is the relationship between structure and objects: tables and particles • Response: eliminativism (about ordinary objects) • Dilemma: Tables don’t exist but ‘Tables exist’ appears to be true!

17. What is the relationship between structure and objects: tables and particles • Option 1: revise semantics • adopt error theoretic approach • ‘Tables exist’ is simply false • but can still pragmatically use such sentences • cf. mathematics • Option 2: revise truth and/or ontology • Account for appearance in terms of: derivative existence, truth as indirect correspondence, truthmakers …

18. What is the relationship between structure and objects: tables and particles • (Intuition) Derivative existence: • ‘Tables exist’ is true but the sense of ‘exist’ is derivative • cf. Eddington: ‘Tables exist …’ = unfinished sentence • cf. quasi-particles … (B. Falkenburg, Particle Metaphysics (The Frontiers Collection), Berlin: Springer 2007, esp. pp. 243-46) • What finishes it is structure structural conception of existence • What about ‘(Fundamental) structure exists …’? • Nothing further added to knowledge by saying ‘and the physical universe/world structure exists.’ (see S. French, 'Scribbling on the Blank Sheet: Eddington'sStructuralist Conception of Objects', Studies in History and Philosophy of Modern Physics 34, pp. 227-259, 2003.)

19. What is the relationship between structure and objects: tables and particles • Tweak Truth: ‘Numerous statements and thought-contents involving posits of common sense and science are true, even though the correct ontology does not include these posits. … Truth for such statements and thought contents is indirect correspondence.’ (T. Horgan and M. Potrc, Austere Realism, MIT Press 2008, p. 3) (+ impossibility of ontological vagueness  minimalist ontology: one concrete particular (the ‘blobject’) that manifests considerable spatio-temporal structural complexity and local variability)

20. What is the relationship between structure and objects: tables and particles • ‘There are tables’ is true but there are no tables • ‘There are tables is true, under the contextually operative standards governing common usage • ‘There are no tables’ is true, under the much rarer ‘direct correspondence’ semantic standards • Worry: context dependence  relativism (of content)?

21. What is the relationship between structure and objects: tables and particles • Try Truthmakers • Retain truth and direct correspondence but reconsider what makes statements true • Armstrong: the truthmaker for ‘x exists’ is (always) x • Cameron: the truthmaker for ‘x exists’ may not be x (R. Cameron, ‘Truthmakers and ontological commitment: or how to deal with complex objects and mathematical ontology without getting into trouble’, Philosophical Studies (2008) 140:1–18)

22. What is the relationship between structure and objects: tables and particles • ‘Tables exist’ is true but deny ontological commitment to tables • ‘Tables exist’ made true by ‘simples’ (arranged table-wise) • retains literal (non-contextual) truth of sentences • captures intuition that complex objects exist, in a derivative sense, but don’t really exist • what really exist are the ‘simples’ • Worry: simples? (cue meerkat) • release from s-t constraint

23. What is the relationship between structure and objects: particles and structure • Particles? • QFT concerns • ‘Particles exist…’ (expressed in ‘practical language of elementary particle dynamics’) in structural sense of existence; i.e. particles exist as aspects of structure • ‘Particles exist’ is (contextually) true in indirect correspondence sense; i.e. there are no particles (as objects), just structure or aspects thereof • ‘Particles exist’ is (literally) true but there are no particles as objects; i.e. truthmakers = structure or aspects thereof (arranged particle-like)

24. What is the relationship between structure and objects: particles and structure • Simples = particles-as-objects? • No: recall motivations for structural realism • Simples = quantum fields, s-t structure… • monadic structuralism: there is only the ‘world structure’ • cf. Horgan and Potrc’s ‘blobjectivism’ • complexity recovered via ‘manners of instantiation’ • pluralistic structuralism: inter-related structures at fundamental level • hierarchical structuralism: inter-related structures between levels • instantiation? dependence??

25. What is the relationship between structure and objects: fusion? • Stick with truth, resist truthmakers: • Mereological bundle theory • Key move: ‘our knee-jerk way of thinking about the things physicists describe as “objects” or “particles” as little material-like hunks of stuff is fundamentally mistaken.’ (L.A. Paul, ‘Parthood and Individuation in a One-Category Ontology’ forthcoming) • World not built from bottom up, ‘spatio-temporal hunk by spatiotemporal hunk’

26. What is the relationship between structure and objects: fusion? • Only category: properties • ‘objects’ = bundles of properties • bundling = qualitative composition • qualitative composition is restricted ‘My personal preference is for a contingent, purely qualitative mereological bundle theory where spacetime, as well as everything else there is, is constructed from fusions of properties.’ • Properties = polyadic structure • Worry: overlapping parts? • role of contingent constraints

27. What is the relationship between structure and objects: fusion? • Bringing together the blob and the bundle: • blob = world structure • ‘global’ bundling of polyadic properties  structure • ‘local’ bundling of polyadic properties  ‘objects’ • costs: manners, parts etc. • keep costs down: look to the physics • fundamental: dependence

28. What is the relationship between structure and objects: dependence? • laws  properties • group structure fundamental objects & composites • e.g. development of the quark model from the SU(3) approach • settling the structure effectively settles the question of which hadrons exist (McKenzie, forthcoming) • group theory as ‘analysis’ of composition

29. What is the relationship between structure and objects: dependence? • (ODS) Fundamental physical ‘objects’ depend on the relevant structure. (cf. Ø.Linnebo, (2008), ‘Structuralism and the notion of dependence’ Philosophical Quarterly, 58, 59–79) • Dependence can take various forms (cf. E.J. Lowe, E. J., ‘Ontological dependence’, StanfordEncyclopaediaof philosophy, (2005). http://plato.stanford.edu/entries/dependence-ontological/) (See: S. French, ‘The interdependence of structure, objects and dependence’ forthcoming in Synthese)

30. What is the relationship between structure and objects: dependence • Identity Dependence: • (ID) ‘objects’ depend for their existence onstructure =df necessarily, the identity of such objects is dependent on the structure • Fits with Non-Eliminativist OSR (and Stachel on space-time) • Worry: if all properties + identity of bearers of relations cashed out in terms of latter, then what is doing the bearing?

31. What is the relationship between structure and objects: dependence • Constitutive Dependence: • (CD) ‘objects’ depend for their existence onstructure =df necessarily, the constitutive nature/ ‘essence’ of such objects is dependent on the structure • captures intuition behind derivative existence • Fits with Eliminativist OSR

32. Back to Composition • Recall GCQ: what is composition? • van Inwagen: The xs compose yiff no two of the xs occupy overlapping regions of space and y occupies the sum of the regions of space occupied by the xs. • Don’t need to go to distant possible world to have doubts about this • Hawley: different answers for different things • But: cf identity criteria • underdeterminationabandon identity criteria (ElimOSR) • structuralism  abandon (general) object based composition

33. Simples, Blobs and Structures • SCQ as constraint: ‘right’ ontology must provide systematic and general answer to SCQ: When do several distinct objects compose an object? • derivative existence: composite objects ‘exist’, but not really • Answer to SCQ: never (no composite objects) • blobjectivism: only one concrete particular • no composite objects • Answer to SCQ: never (only one real object) • truth-makers: many simples • (putative) composite objects are ‘ontological free lunch’ (Cameron, Truth-Makers and Ontological Commitment) • Answer to SCQ: never (no collection of objects ever composes)

34. Simples, Blobs and Structures • ElimOSR: no objects, composite or composing • Answer to SCQ: never (no composing objects) • monadic structuralism sim. to blob • pluralistic structuralism sim. to simples • Non-ElimOSR: ‘thin’ objects • Answer to SCQ: never (objects too thin to compose)

35. Science, metaphysics and the philosophy of science • Stating the obvious: • physics-lite metaphysics runs the risk of floating free (L&R p. 9) • metaphysics-lite realism runs the risk of incomprehension

36. Science, metaphysics and the philosophy of science • Suggesting the less obvious (perhaps): • Humility allows insulation of metaphysics from physics (cf. Ladyman and Ross p. 22, on Merricks) • e.g. are simples individuals or not? • physics can’t answer (underdetermination) • Lower standards and suppress humility to accommodate physics • reduce no. of unknowable metaphysical facts by reducing basis for such facts (e.g. objects)

37. Science, metaphysics and the philosophy of science • Cut our metaphysical cloth to fit the physics, with the philosopher of science as tailor!