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Physics and the ‘Real Patterns’ theory of ontology’ James Ladyman.

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1 Physics and the ‘Real Patterns’ theory of ontology’ James Ladyman

2 Thanks to Joss and Richard and the Lorentz Centre The document that describes the topic of the conference does a great job of identifying a lot of important and fascinating issues. Thanks to the physicists for informing us about the relevant phenomena. My ideas owe a lot to my co-authors Steven French and Don Ross. The material on phlogiston is forthcoming in a paper in Synthese

3 Three Ideas 1.Structure is retained on theory change even when ontology is not. 2.Structuralism about a domain involves the idea that the entities in the domain are mutually dependent on each other for their existence/individuation. 3.Real Patterns –In the case of physical structures I contend that these three ideas all centrally involve modality.

4 Of what is everything made? Western philosophy allegedly started when the pre-Socratics asked this question. This is a metaphysical question physics is supposed to answer. It presupposes that the world comes in a hierarchy of levels and that there is a fundamental level with a few basic kinds of entities. The most naïve picture is one of physical objects ordered by (spatial) size and ultimately composed of elementary particles.

5 Levels There is not necessarily a single hierarchy Ordering by spatiotemporal scale Ordering by energy Ordering by composition Anomalous sciences: evolution, game theory, economics, thermodynamics,

6 Scepticism about Levels Spatiotemporal scale may not be a fundamental feature of reality. It is an open question whether quantum gravity will take the spatiotemporal manifold as primitive rather than emergence. The same may be true of the energy scale. The levels structure based on the composition relation is undermined by the fact that the notion of composition does not translate well into physics: Of what are quasiparticles composed? Are particles composed of quantum fields? What composes a black hole?

7 1. Theory Change as a Motivation for Structuralism Antirealism: science saves the phenomena Realism: science describes the furniture of the world Structural Realism: science tells us about the structure of the world - more than merely saving the phenomena but less than full ontological commitment –Example: even the existence of central theoretical entities is necessary for more than empirical adequacy.

8 The Theory of Phlogiston Burning is a process in which a principle of combustion is given off by the fuel and enters the air.

9 The Theory of Phlogiston Burning is a process in which a principle of combustion is given off by the fuel and enters the air. All flammable substances are supposed to contain phlogiston and it is what all metals have in common.

10 The Theory of Phlogiston Burning is a process in which a principle of combustion is given off by the fuel and enters the air. All flammable substances are supposed to contain phlogiston and it is what all metals have in common. There is no such substance and ordinary combustion is the addition of oxygen to something and not the emission of something by the fuel.

11 The Theory of Phlogiston Burning is a process in which a principle of combustion is given off by the fuel and enters the air. All flammable substances are supposed to contain phlogiston and it is what all metals have in common. There is no such substance and ordinary combustion is the addition of oxygen to something and not the emission of something by the fuel. So it seems obvious that phlogiston theory must be bad science.

12 The Theory of Phlogiston (heyday ) Becher ( ) proposed combustible earth (as one of three earths composing ordinary substances).

13 The Theory of Phlogiston (heyday ) Becher ( ) proposed combustible earth (as one of three earths composing ordinary substances). Stahl ( ) proposed phlogiston in 1697 (also year the world’s first heat engine was built): parallels between metals heated in air (calcination) and ordinary combustion – creation of dust and light often given off, lots of air needed. Phlogiston given off in combustion - flames

14 The Theory of Phlogiston (heyday ) Becher ( ) proposed combustible earth (as one of three earths composing ordinary substances). Stahl ( ) proposed phlogiston in 1697 (also year the world’s first heat engine was built): parallels between metals heated in air (calcination) and ordinary combustion – creation of dust and light often given off, lots of air needed. Phlogiston given off in combustion - flames Wood turns to ash when burnt (phlogiston must therefore have mass). Iron rusts to calx also giving off phlogiston. Charcoal combusts almost completely so charcoal is very nearly pure phlogiston.

15 The Theory of Phlogiston (heyday ) Becher ( ) proposed combustible earth (as one of three earths composing ordinary substances). Stahl ( ) proposed phlogiston in 1697 (also year the world’s first heat engine was built): parallels between metals heated in air (calcination) and ordinary combustion – creation of dust and light often given off, lots of air needed. Phlogiston given off in combustion - flames Wood turns to ash when burnt (phlogiston must therefore have mass). Iron rusts to calx also giving off phlogiston. Charcoal combusts almost completely so charcoal is very nearly pure phlogiston. Phlogiston was supposed to have a metallic quality. Metal calx burnt in charcoal becomes ordinary metal - adding phlogiston adds the metallic quality to the true form (calx) of the metal (practical application to copper mining).

16 The Theory of Phlogiston (heyday ) Becher ( ) proposed combustible earth (as one of three earths composing ordinary substances). Stahl ( ) proposed phlogiston in 1697 (also year the world’s first heat engine was built): parallels between metals heated in air (calcination) and ordinary combustion – creation of dust and light often given off, lots of air needed. Phlogiston given off in combustion - flames Wood turns to ash when burnt (phlogiston must therefore have mass). Iron rusts to calx also giving off phlogiston. Charcoal combusts almost completely so charcoal is very nearly pure phlogiston. Phlogiston was supposed to have a metallic quality. Metal calx burnt in charcoal becomes ordinary metal - adding phlogiston adds the metallic quality to the true form (calx) of the metal (practical application to copper mining). When something burns in a sealed container it uses up the oxygen in the air until eventually the fire goes out. This was explained in terms of the saturation of the air with phlogiston. Combustion, respiration and calcification are all the same kind of reaction (oxidisation). (Animals in a sealed chamber phlogisticate the air (Boyle).)

17 The Theory of Phlogiston Big Problem Since Rey (1630) it was known that the calx of a metal could be heavier than its metallic form. Some Stahlians posited negative weight for metallic phlogiston but most believed that impurities caused the weight increase.

18 Priestley ( ) Plants dephlogisticate the air (cycle between plants and animals). Air without any phlogiston is air whose potential to be burnt is maximal. Dephlogisticated air by heating a calx (red mercury) (1774) Scheele ( ): ‘fire air’ (1771-2, published 1777) There is a clear sense in which the dephlogisticated air that Priestley describes breathing is oxygen.

19 Priestley ( ) Plants dephlogisticate the air (cycle between plants and animals). Air without any phlogiston is air whose potential to be burnt is maximal. Dephlogisticated air by heating a calx (red mercury) (Priestley 1774) Scheele ( ): ‘fire air’ (1771-2, published 1777) There is a clear sense in which the dephlogisticated air that Priestley describes breathing is oxygen. Phlogisticated air is air saturated with phlogiston. Inflammable air [hydrogen (Cavendish 1766)] is pure phlogiston not charcoal according to Cavendish. Priestley burned metal oxide in inflammable air to make pure metal (and water) - reduction inverse of oxidisation. But inflammable air is obviously not just ordinary air with phlogiston in higher concentration, since ordinary air becomes saturated with phlogiston during combustion and eventually the fire goes out. Some of the phlogisticated air dissolves in water (carbon dioxide) and some does not (mostly nitrogen). Neither supports ordinary combustion (like Oxygen) or reduction (like hydrogen).

20 Lavoiser ( ) Oxygen (dephlogisticated air) and hydrogen (phlogisticated air) found in compound ordinary air and make up water. Burning, respiration and rusting of iron are all oxidisation. But he also thought all acids contain oxygen and that oxygen was a principle not an element.

21 Realists on Phlogiston Among philosophers ‘phlogiston’ is a prime example of a non-referring theoretical term. “phlogiston refers to nothing” (Psillos) ‘Phlogiston’ is a counterexample to the simple causal theory since then it would refer to oxygen (whatever is involved in combustion) (Bird)

22 Phlogiston’s Success Explains loss of weight of wood, coal and ordinary substance when burnt. Charcoal leaves hardly any ash because it is almost pure phlogiston. Air saturated with phlogiston cannot support respiration. Metal + heat (in air) = calx [metal oxide] + phlogisticated air [de-oxygenated air] Calx + charcoal (source of phlogiston) = metal (+ fixed air [carbon dioxide (Joseph Black ( ) 1754)]) So Metal = calx + phlogiston (explaining what metals have in common) Charcoal = calx (fixed air) + phlogiston Metal + acid = salt + inflammable air (note Lavoisier thought acids had to contain oxygen) Metal + water = calx + inflammable air (Water = inflammable air [hydrogen] + dephlogisticated air [oxygen]) Dephlogisticated marine acid (Scheele) = chlorine (Davy). novel prediction: heat calx in inflammable air to get pure metal novel prediction of new acids by Scheele (formic acid, lactic acid) Animals and plants have opposite effects on the air - the former phlogisticate and the latter dephlogisticate Metals are alike (lost by intermediary science between Priestley and electronic chemistry). Phlogistication and dephlogistication are inverse chemical reactions (reduction and oxygenation)

23 ‘phlogistication’ and ‘dephlogistication’ can be regarded as referring to the processes of oxidation and reduction, where these are understood in the general sense of the formation of an ionic bond with an electronegative substance, and the regaining of electrons respectively.

24 If the oxidising agent is oxygen, and the oxidised compound is a source of carbon then the product is carbon dioxide i.e. fixed air. (combustion of fossil fuels) If the oxidising agent is an acid, then hydrogen is emitted.

25 ‘phlogistication’ and ‘dephlogistication’ can be regarded as referring to the processes of oxidation and reduction, where these are understood in the general sense of the formation of an ionic bond with an electronegative substance, and the regaining of electrons respectively. If the oxidising agent is oxygen, and the oxidised compound is a source of carbon then the product is carbon dioxide i.e. fixed air. If the oxidising agent is an acid, then hydrogen is emitted. We could go further and allow that ‘phlogiston rich’ and ‘phlogiston deficient’ refer too, namely to strongly electro-negative and electro-positive molecules respectively. One could even argue that ‘phlogiston’ refers to electrons in the outer orbital of an atom.

26 Forgotten Wisdom: Whewell, History of the Inductive Sciences “But we must not forget how natural it was to suppose that some part of a body was destroyed or removed by combustion…It would be easy to show, from the writings of phlogistic chemists, what important and extensive truths their theory enabled them to express simply and clearly.” Combustion, respiration and calcination of metals are all the same kind of reaction and there is an inverse kind of reaction too.

27 Structural Realism John Worrall (1989) introduced structural realism (although he attributes its original formulation to Poincaré). Using the case of the transition in nineteenth century optics from Fresnel's elastic solid ether theory to Maxwell's theory of the electromagnetic field, Worrall argues that: “There was an important element of continuity in the shift from Fresnel to Maxwell – and this was much more than a simple question of carrying over the successful empirical content into the new theory. At the same time it was rather less than a carrying over of the full theoretical content or full theoretical mechanisms (even in approximate form)... There was continuity or accumulation in the shift, but the continuity is one of form or structure, not of content (1989, 117).

28 More Structural Realism Instructive historical examples:  The transition from Fresnel’s ether theory of light to Maxwell’s electromagnetic field theory.  The transition from Galilean relativity to Lorentz invariance.  The transition from classical mechanics to quantum mechanics.  The transition from Newtonian gravitation to General Relativity.

29 Modality We have been very focused on the composition of wholes by parts and have not addressed the key issue of the status of putative causal claims at different levels. More generally, I consider modality to be a central issue for the philosophy of physics. (Counterfactual definiteness + Locality is sufficient to prove Bell’s theorem (cf. Tomasz Bigaj in SHPMP).)

30 Modality Realism: physics tells us about causation, the laws of nature and deep metaphysics Antirealism: physics gives maximally general descriptions of regularities in the phenomena

31 Modality Realism: physics tells us about causation, the laws of nature and deep metaphysics Antirealism: physics gives maximally general descriptions of regularities in the phenomena oExample: the speed limit of light speed - is it merely a generalization that is true or does it have some kind of necessary status?

32 Modality Realism: physics tells us about causation, the laws of nature and deep metaphysics Antirealism: physics gives maximally general descriptions of regularities in the phenomena oExample: the speed limit of light speed - is it merely a generalization that is true or does it have some kind of necessary status? oExample: the laws and the constants and the fine- tuning argument

33 Is Physics Special and is fundamental physics special with respect to the rest of physics? “In science there is only physics; all the rest is stamp collecting.” Ernest Rutherford

34 The Incompleteness of the Special Sciences In all the special sciences it is acceptable to invoke entities and processes from more fundamental sciences in explanations. For example, the economy may be affected by the weather, living systems may be affected by radiation, chemical reactions may be affected by magnetic fields, and so on. There is a fundamental asymmetry between physics and the special sciences.

35 The Completeness of Physics Fundamental physics aspires to a kind of completeness in so far as it is never permitted to invoke entities or processes from the special sciences in an explanation of the behaviour of the the fundamentally physical. Physics is analytically complete since it is the only science that cannot be left incomplete.

36 Fundamental Physics Measurements at all scales and at all locations in spacetime are potential falsifications or confirmations of fundamental physics. This is not true of any other science. Fundamental physics may not exist other than as a limiting ideal (if there is no fundamental level). (Many parts of physics are special sciences.)

37 The Primacy of Physics Constraint (PPC) Naturalists ought only to accept a form of physicalism that is motivated by reflection on the history of science and the nature and practice of contemporary science. Ladyman and Ross argue that this justifies nothing more than the PPC (methodological physicalism): “Special science hypotheses that conflict with fundamental physics, or such consensus as there is in fundamental physics, should be rejected for that reason alone. Fundamental physical hypotheses are not symmetrically hostage to the conclusions of the special sciences.” (2007, 44) This leaves it open to the naturalist to believe both that the entities posited by the special sciences exist, and that the causal relations posited by them are genuine.

38 2. Structuralism and the Part- Whole relation The natural numbers are often said to ontologically depend on each other and the relations among them - so the parts depend on the whole. Cf. the identity and individuality of spacetime points depends on the metric field and hence again the parts depend on the whole.

39 Structuralism: less than ontological commitment to the dressing theory is given; more than relations among the phenomena.

40 Objects and Individuals What does it take to be an object? What does it take to be an individual? Quasi-particles, Bose Einstein Condensates, Cooper pairs, entangled photon pairs, quantum fields… Do they ‘exist’ in the same sense as tables and chairs?

41 Individuation PII and weak discernibility - structures admitting a non-trivial automorphism - complex plane, fermions in the singlet state (Michal) purely relational individuation an asymmetric graph of order 6: pure relations can give rise to absolute discernibility

42 Quasi-Particles Bipolaron a bound pair of two polarons Chargon a quasiparticle produced as a result of electron spin-charge separation Configuron an elementary configurational excitation in an amorphous material which involves breaking of a chemical bond Electron holea lack of electron in a valence band Exciton a bound state of an electron and a hole Fracton a collective quantized vibration on a substrate with a fractal structure. Holon a quasi-particle resulting as a result of electron spin-charge separation Libron a quasiparticle associated with the librational motion of molecules in a molecular crystal Magnon a coherent excitation of electron spins in a material Phason vibrational modes in a quasicrystal associated with atomic rearrangements Phonon vibrational modes in a crystal lattice associated with atomic shifts Plasmon a coherent excitation of a plasma Polaron a moving charged quasiparticle that is surrounded by ions in a material Polariton a mixture of photon with other quasiparticles Roton elementary excitation in superfluid Helium-4 Soliton a self-reinforcing solitary excitation wave Spinon a quasiparticle produced as a result of electron spin-charge separation

43 3. Real Patterns macroscopic objects as relatively stable and enduring patterns that emerge within the structure of the quantum state of the world. On such a view, the world need not form a compositional hierarchy, with or without ultimate parts.

44 Special Science Ontology In science one is only interested in recovering the statistical properties of low-level entities when tracking high level ones. Coarse-graining and approximation are necessary for special science ontologies to emerge. This explains why even token identities do not obtain between say a cat and its constituent atoms. In the special sciences one is usually interested in ‘universal’ forms of behaviour, where ‘universal’ means independent of microphysical or lower level constitution. The identification of universality and the appropriate descriptive categories for tracking it is one of the principle tasks of the special sciences. The scale relativity of ontology (Ladyman and Ross) The renormalization group view of the world (Sokal and Bricmont): the renormalization group describes transformations that allow the number of degrees of freedom in the Hamiltonian of a system to be massively reduced while still recovering the critical behaviour of the system.

45 Complexity The special sciences are possible because the world is to some extent algorithmically compressible. At certain levels of description it is possible to use much less information to predict the behaviour of systems described in an approximate and probabilistic way, than would be needed to describe their microstates. For example, Kepler’s laws, the ideal gas laws, the Hardy– Weinberg law,… In fact all laws in the special sciences are like this. The special sciences rely upon reduction in the degrees of freedom of the system. There are real patterns in the world that are only visible at the right scales of resolution and degrees of approximation. If you don’t see them you are missing something about reality and that is good enough to allow us to say that the objects, properties and processes described by the special sciences are real.

46 Computational Approaches to Emergence between order and randomness logical depth, thermodynamic depth, statistical complexity, information theoretic entropy, algorithmic complexity,… complex systems involve hierarchical organisation.

47 Real Patterns Daniel Dennett’s notion of ‘real pattern’ is a computational one. The idea is based on the compression of data and the reduction of information processing made possible by a high level description of a system that could in principle be described at a fine-grained level but at a much greater computational cost.

48 John Conway’s ‘Game of Life’ is based on a simple implementation of cellular automata that makes a particular range of stable dynamic attractors highly salient to people. A person using the system naturally book-keeps its state sequences by reference to a typology of ‘emergent’ objects—‘gliders’, ‘eaters’, ‘spaceships’, etc.—that have only virtual persistence. (That is, two successive instances of ‘the same’ glider share only structure, and common participation in structures larger than themselves. A glider is clearly mereologically composed of a small number of illuminated cells. However, its successive instances are composed of different cells, and successive instances a few steps apart have no cells in common.) Once this descriptive stance is adopted towards Life, almost all users spontaneously track the dynamics in terms of causal interactions among instances of these types—for example, a glider will be caused to disappear through interacting with an eater. That is, Life users naturally begin logging causal generalizations about the types of virtual objects, and thereby seem to commit themselves to their objective existence. (All the above paragraphs are taken from Ladyman and Ross (2007), chapter 4.)

49 –One should be cautious in using the Game of Life as a metaphysical model of the universe. –It is useful for the purposes to which Dennett puts it, because it shows how patterns can emerge at grains of analysis coarser than the grain at which what is analogous to the fundamental microphysical level is studied, even when all causal processes governing the latter are non-complex, known, measurable, and deterministic. Life is thus a good antidote to romantic interpretations of emergence. –However, because in Life there is an unambiguous fundamental level composed of the aggregation of a finite number of little things, and because no higher-level object types cross-classify the dimensions of any models of the game relative to classifications in terms of cells, Life differs greatly from the universe with respect to the kinds of reductionism sustainable in it. Life admits of complete decomposition; the universe might not. (All the above paragraphs are taken from Ladyman and Ross (2007), chapter 4.)

50 Definition of Real Patterns (Ladyman and Ross, 2007, chapter 3 To be is to be a real pattern; and a pattern is real iff I.it is projectible under at least one physically possible perspective; and, II.it encodes information about at least one structure of events or entities S where that encoding is more efficient, in information-theoretic terms, than the bit-map encoding of S, and where for at least one of the physically possible perspectives under which the pattern is projectible, there exists an aspect of S that cannot be tracked unless the encoding is recovered from the perspective in question.

51 According to RP, the utility of the intentional stance is a special case of the utility of scale-relative perspectives in general in science, and expresses a fact about the way in which reality is organized—that is to say, a metaphysical fact. The fact in question is what we (but not Dennett) call the scale relativity of ontology. Scale relativity of epistemology isn’t controversial. To borrow an example from Wallace (2001), if you want to predict what a hungry tiger will do when confronted with a deer, you should study whole behavioural patterns of whole tigers, not individual tiger cells or molecules. It is clearly motivated by any thesis to the effect that models of complex systems are scientifically useful. (All the above paragraphs are taken from Ladyman and Ross (2007), chapter 4.) trade offs between scope, accuracy and simplicity

52 Real patterns are preserved on theory change - cf. Butterfield on the Krebs cycle.

53 Dennett’s paper is notoriously unclear about whether ‘real patterns’ should be regarded as real or as useful fictions. realism versus pragmatism - metaphysics versus epistemology

54 Conservative metaphysicians would complain, the eater is a redundant causal factor, since the program underlying Life, which in its declarative representation quantifies only over cells, is strictly deterministic. We are reminded that an eater or a glider is, at any given time, ‘made of’ cells and nothing else. Then we are invited to agree that a thing cannot have causal efficacy over and above the summed causal capacities of the parts with which it is allegedly identical. The result is supposed to be reductionism, and instrumentalism about gliders and eaters. (The above paragraph is from Ladyman and Ross (2007), chapter 4.)

55 Real patterns are defined modally. They are there to be discovered.

56 David Wallace advocates what he calls a functionalist account of ontology based on the notion of real patterns in his elucidation of the Everettian interpretation of quantum mechanics. His ontology is two-tier in that only higher-order entities such as cats and tables are understood in terms of real patterns, whereas the wavefunction or whatever else proves to be fundamental in physics is understood in categorical rather than functional terms.

57 On the other hand, James Ladyman and Don Ross (2007) advocate a real patterns account of ontology across the board. All real patterns are real but there is an asymmetric relation among them. The relation is not composition since emergent structure is not reducible to the sum of the parts - no building blocks (Healey)

58 Real patterns theory can be developed in terms of the dynamics of phase spaces rather than in computational terms. (Jenann Ismael suggested this.) Reducing the number of degrees of freedom by finding ‘objects’. There are synchronic patterns too of course but they could be represented in terms of laws of co-existence.


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