Contribution
It connects two literatures that had developed separately. Effective realism (ER) was developed in BJPS for QM, QFT and superseded theories, while Ladyman–Ross OSR had already invoked “effective ontology”. The paper argues that OSR is the metaphysics ER needs to count as realism, and that it unifies the three ERs under one account. It adds a reply to Egg’s (2019) critique of the structural-realist treatment of QM.
Key insight
“Effective” theories need not be read instrumentally if existence is itself scale-relative. What a theory gets right is modal structure within its domain, and the things it posits are real patterns at that scale. Superseded and non-fundamental theories then have real ontologies that do not compete with deeper ones, and a realist can believe in both Newtonian forces and curved spacetime without contradiction.
Assumptions
- OSR as in Ladyman & Ross (2007): “the world has an objective modal structure that is ontologically fundamental, in the sense of not supervening on the intrinsic properties of a set of individuals” (p. 7, quoting L&R p. 130).
- The real-patterns criterion (Ross 2004 version, p. 9): a pattern is real iff it is projectible under some physically possible perspective, and it encodes information about some structure S more efficiently, “in information-theoretic terms”, than the bit-map encoding of S, with some aspect of S untrackable without it.
- Scale relativity of ontology: existence claims are relativised to the scales at which nature is measurable (L&R p. 200).
- Decoherence yields an effective collapse shared by all versions of QM, and “for each observer … it is an objective fact which branch is effectively selected” (p. 5).
- Every current physical theory is effective, except perhaps thermodynamics (fn. 2). There is no fundamental level (fn. 9).
Key results
What it argues:
- §2.1 (QM): Fraser & Vickers restrict realist commitment to what all realist versions of QM share (decoherent branches as physically possible outcomes), but they concede their view lacks a metaphysics. Egg’s functionalist ontology fails, both by being hard to apply to modal claims and through Saatsi’s inconsistency objection. OSR supplies the metaphysics: those modal claims commit us to objective modal structure represented by branching structure, which even Everett accommodates (Wallace 2010). F&V are “already implicitly committed” to OSR, being realist but quietist about fundamental ontology. Real patterns plus scale relativity answer Saatsi.
- §2.2 (Egg 2019): OSR can be verificationist about unobserved measurements without anthropocentrism, by appealing to decoherence rather than observers. The authors claim Egg’s challenge rests on the “misguided opinion that an anthropocentric notion of measurement is mandatory for the structural realist” (p. 12).
- §3 (QFT): Williams’ ER and Fraser’s renormalisation-group realism are open to Ruetsche’s charge that they amount to empirical adequacy plus pragmatic commitment, which is indistinguishable from van Fraassen’s empiricist structuralism. Adding realism about modal structure (the RG-invariant, “robust” long-distance structure represents modal structure in the world) makes them genuinely realist. The scale dependence they stress is an instance of general scale relativity.
- §4 (old theories): Robertson & Wilson’s theoretical relicts (e.g. Galilean spacetime, Newtonian gravity) are embedded in OSR via real patterns, as with phlogiston’s correct identification of combustion, calcination and respiration as one kind of process (Ladyman 2011). Improvement: replace R&W’s “levels of abstraction” with energy scales, since the Poisson equation is the low-energy limit of GR (p. 18).
- §5: the three ER debates are unified under OSR; “Structural realism should thus be brought back into the debate.”
Claims
| id | claim | strength | support |
|---|---|---|---|
| C1 | The three extant ERs lack an explicit realist metaphysics and risk collapsing into constructive empiricism or structural empiricism | moderate | informal argument, largely drawing on the ER authors’ own admissions (F&V §3.4) and Ruetsche 2018, 2020 (§§2.1, 3) |
| C2 | OSR’s realism about modal structure supplies that metaphysics and makes each ER genuinely realist | weak | informal argument by fit. Commitment to “objective modal structure” is what distinguishes realism from van Fraassen, but it is asserted rather than defended against modal anti-realism |
| C3 | Scale-relative real-patterns ontology avoids Saatsi’s inconsistency objection | moderate | argument: theories at different scales make non-rival claims (pp. 9–10, 18–19). The cost, scale-indexed existence, is accepted rather than argued for |
| C4 | Decoherence lets OSR be verificationist about measurement without anthropocentrism, answering Egg 2019 | weak | short reply (pp. 12–13). Decoherence’s own measurement-problem limits are not discussed; “effective” collapse is assumed adequate |
| C5 | Fraser & Vickers are “already implicitly committed” to OSR | weak | textual reading of F&V’s modal quietism (p. 8) |
| C6 | Scale relativity improves on Robertson & Wilson’s “levels of abstraction” | weak | a single example (Newton as the low-energy limit of GR, p. 18); no general argument that abstraction and scale come apart where it matters |
Method
Philosophical synthesis. It reviews three ER proposals, identifies a shared gap (the metaphysics of realism), and argues that one existing framework fills it, with replies to two named objections (Saatsi 2022, Egg 2019). It introduces no formal apparatus.
Concepts
- Effective realism (ER): scientific realism about effective theories, those with a limited range and domain of applicability. Effective ontology is such a theory’s ontology.
- OSR (this paper’s sense): the Ladyman–Ross framework, meaning modal-structure realism plus real patterns plus scale relativity, including Rainforest Realism. “Fundamental” means non-supervenient on intrinsic properties, not bottom-level.
- Real pattern: see Assumptions. It is a compression criterion relative to physically possible perspectives.
- Scale relativity of ontology: what exists is indexed to the scales at which nature is measurable. Mountains do not exist at the quantum scale.
- Theoretical relicts (Robertson & Wilson): posits of superseded theories retained, domain-restricted, as effective entities.
- Selective realism: identifying in advance the parts of theories that will survive change. The authors distinguish ER from it (fn. 17).
Connections
It applies the Ladyman–Ross OSR described in LIT-045 (whose author is Ladyman) to the effective-theory debate. Its “fundamental without a fundamental level” (fn. 9) contrasts with Morganti’s (LIT-173) coherentism, which keeps objects fundamental and demotes relations to dependence. Floridi (LIT-152) also invokes Dennett’s real patterns, via Wallace 2003, but as a software-engineering analogy rather than a compression criterion. Wallace’s mathematics-first structural realism (LIT-151) is the natural companion; the dossier’s “p113” is LIT-151. This paper cites Wallace’s QFT and decoherence work, not that paper. Karpenko (LIT-215, fn. 3) cites I.E. Pris (2024), “Effective ontic structural realism and contextual realism”, a Russian-language response to this programme.
Metaphysics: the work defends realism about modal structure, a real-patterns criterion of existence, scale-relative existence, and the denial of a fundamental level. These are theses about what it is to exist, so the tag is justified.
Bearing on the record
It carries nothing for ML practice. One conceptual point touches ML only as an analogy: the real-patterns criterion is explicitly information-theoretic, a pattern is real if it compresses better than a bit map and is projectible, and so sits near MDL-style accounts of structure. The paper draws no such connection, and the record should not credit it with one. In this record it is the reference for “effective” and scale-relative ontology in the structural-realism cluster.
Limitations
- The arguments depend on the Ladyman & Ross (2007) framework and are not defended here. Readers who reject modal-structure realism or real patterns get no independent argument.
- The reply to Egg is two paragraphs. Leaning on decoherence and “effective” collapse leaves the standard objection unaddressed, that decoherence alone does not select outcomes.
- “Scale” is used for both energy scale (QFT, Newton–GR) and measurement scale (mountains, viruses). Newtonian gravity is the weak-field, slow-motion limit of GR, which is not straightforwardly an energy-scale limit, so C6 rests on a loose identification.
- The paper uses the simpler Ross (2004) real-patterns definition and cites it to L&R 2007’s page number (fn. 11 flags this).
- It concedes that French, Ladyman and Ross do not treat SR as selective realism, while framing selective-realist ERs within OSR (fn. 17). How far the fit extends is left open.
Open questions
- Does “exists at scale s” say more than “is a real pattern at scale s”? The paper treats them as equivalent, so scale-relative existence may be definitional.
- Can realism about modal structure be distinguished from van Fraassen’s structural empiricism by anything other than the realist’s say-so? An account of what modal structure is would settle C2.
- Does the decoherence reply generalise to cases without a clear system/environment split, e.g. cosmology, as Egg’s unobserved-measurement cases suggest?
Corrections to the seeded skim
- The dossier says to “check whether it answers Saatsi-style worries about the quantum case”. Saatsi’s (2022) objection, as reported here, is not about the quantum case. It says Egg’s functionalist effective ontology over-generates inconsistent ontology, with the example Newtonian gravitational forces vs GR gravitation. The paper answers it directly with scale relativity, in §2.1 (pp. 9–10) and again in §4 (pp. 18–19).
- The dossier says §2.2 “rebuts Egg’s challenge that structural realism cannot dissolve the measurement problem”. More exactly, Egg (2019) argues that dissolving the measurement problem, the Ladyman–Ross Bohrian or verificationist move, “is not an option for the realist”, because an unsupplemented Born rule makes regularities hold only when observers are present (anthropocentrism). The reply keeps “a kind of verificationist stance” but replaces anthropocentric measurement with decoherence and effective collapse (pp. 12–13), citing Schlosshauer & Camilleri’s decoherence reading of Bohr.
- The abstract names Fraser & Vickers for ER about QM, but the introduction and §2.1 credit Egg (2021) as a co-originator, whose functionalist effective ontology is then rejected in favour of OSR.
- The real-patterns definition quoted as “Ladyman and Ross [2007], p. 226” is, by the authors’ own footnote, Ross’s (2004) original, not the refined 2007 version (logical depth). The simpler one is used “because it … fulfils our goals” (fn. 11).
- Ladyman & Lorenzetti accept underdetermination among QM interpretations only for the sake of engaging the literature (fn. 4, citing Wallace, who argues there is none).
- “OSR” here means the whole Ladyman–Ross programme, including Rainforest Realism for the special sciences, and is explicitly contrasted with French’s eliminativism (fn. 1). “Fundamental” means not supervening on intrinsic properties of individuals, not “belonging to a fundamental level”; Ladyman–Ross deny there is one (fn. 9).
- metaphysics tag: justified. The paper defends realism about objective modal structure, the thesis that to be is to be a real pattern, and scale-relative existence with no fundamental level; it is explicitly offered as “a metaphysics for ER”. philosophy-of-science correctly leads, since the debate is about scientific realism, and quantum-foundations fits §2.