David Wallace's 'Dennett's Criterion' plays a key part in establishing realist claims about the existence of a multiverse emerging from the mathematical formalism of quantum physics, even after decoherence is fully appreciated. Although the philosophical preconditions of this criterion are not neutral, they are rarely explicitly addressed conceptually. I tease apart three: (I) a rejection of conceptual bridge laws even in cases of inhomogeneous reduction; (II) a reliance on the pragmatic notion of usefulness to highlight quasi-classical patterns, as seen in a decoherence basis, over others; and (III) a structural realist or 'functional realist' point of view that leads to individuating those patterns as real macroscopic objects at the coarse-grained level, as they are seen from the Classical Stance (analogous to Dennett's Intentional Stance). I conclude that the justification of Dennett's Criterion will be intimately tied up with the fate of strong forms of naturalism, and in particular that Wallacian quantum mechanics is a key case study for concretely evaluating his 'math-first' structural realism (Wallace 2022).
David Wallace's 'Dennett's Criterion' plays a key part in establishing realist claims about the existence of a multiverse emerging from the mathematical formalism of quantum physics, even after decoherence is fully appreciated. Although the philosophical preconditions of this criterion are not neutral, they are rarely explicitly addressed conceptually. I tease apart three: (I) a rejection of conceptual bridge laws even in cases of inhomogeneous reduction; (II) a reliance on the pragmatic notion of usefulness to highlight quasi-classical patterns, as seen in a decoherence basis, over others; and (III) a structural realist or 'functional realist' point of view that leads to individuating those patterns as real macroscopic objects at the coarse-grained level, as they are seen from the Classical Stance (analogous to Dennett's Intentional Stance). I conclude that the justification of Dennett's Criterion will be intimately tied up with the fate of strong forms of naturalism, and in particular that Wallacian quantum mechanics is a key case study for concretely evaluating his 'math-first' structural realism (Wallace 2022).
David Wallace's The Emergent Multiverse is the most recent complete presentation of a version of Everett's theory of quantum mechanics that has attracted much scientific activity in the past decade. I present a brief sketch ofWallace's solution to the measurement problem, arguing that the many-worlds interpretation is not as far-fetched as it is often conceived to be. Taking the wavefunction as the fundamental ontology, it claims to solve the measurement problem by recognizing certain (quasi-classical) patterns of the wavefunction in 3N-dimensional configuration space that functionally behave like the (classical) configuration-space pattern of a N-particle system described by classical mechanics. In this sense, structures within the universal wavefunction are identified with classical `worlds' at the coarse-grained level. I highlight two elements of this work: the role of emergence and the functionalist framework that Wallace imports through what he calls `Dennett's criterion'. This criterion appeals to the virtue of usefulness (in the form of predictability and explanatory power) as a criterion for the reality of `patterns'. It is shown that, due to decoherence, quasi-classical worlds emerge weakly, similar to that of the emergence of thermodynamic temperature from statistical physics, in the sense that they are autonomous and unexpected with respect to the lower-level domain (as opposed to strong emergence of some insuper et supra high-level ontology). However, the use of Dennett's criterion obscures this result, laying bare some philosophical issues, which we address over three axes of distinctions: (i) the objective/subjective-axis, (ii) the quantitative/qualitative-axis within the framework of intertheoretic reduction and (iii) the ontological/epistemological-axis. First, Daniel Dennett's `real patterns' are compared to Wallace approach to patterns. Then, I point out (i) an analogy with Bas van Fraassen's idea of causal patterns that become salient due to pragmatic explanation, namely that in the context of a pragmatic goal the quasi-classical pattern is made salient over other objectively existing, non-classical, patterns. I conclude that in the absence of human goals there is no reason to regard the quasi-classical pattern as `more real' than other patterns. In analogy to Dennett's `intentional stance', Wallace is committed to a `classical stance', equivalent to breaking Hilbert space democracy of bases. Although Wallace's version is a weaker one, his (ii) relations between theories bare resemblance to the reductionist program, and I argue that, next to quantitative deduction, additional conceptual `bridge principles' à la Ernest Nagel are needed. The appeal to usefulness as a criterion for reality (iii), I claim, is not necessary to solve the measurement problem itself, but has the further (unwarranted) goal of establishing `real' worlds. I spell out a solution to the measurement problem, the many-minds theory, which solves the problem along the same lines as The Emergent Multiverse, with the exception that the - although the quantum world itself is real - the classical worlds with definite properties are beliefs in the superposed brains of observers.
David Wallace's ``The Emergent Multiverse" is the most recent complete presentation of\na version of Everett's theory of quantum mechanics that has attracted much scientific\nactivity in the past decade. I present a brief sketch of Wallace's solution to the measurement\nproblem, arguing that the many-worlds interpretation is not as far-fetched as it is\noften conceived to be. Taking the wavefunction as the fundamental ontology, it claims\nto solve the measurement problem by recognizing certain (quasi-classical) patterns of\nthe wavefunction in 3N-dimensional configuration space that functionally behave like\nthe (classical) configuration-space pattern of a N-particle system described by classical\nmechanics. In this sense, structures within the universal wavefunction are identified\nwith classical `worlds' at the coarse-grained level. I highlight two elements of this work:\nthe role of emergence and the functionalist framework that Wallace imports through\nwhat he calls `Dennett's criterion'. This criterion appeals to the virtue of usefulness\n(in the form of predictability and explanatory power) as a criterion for the reality of\n`patterns'. \n\nIt is shown that, due to decoherence, quasi-classical worlds emerge weakly, similar\nto that of the emergence of thermodynamic temperature from statistical physics, in the\nsense that they are autonomous and unexpected with respect to the lower-level domain\n(as opposed to strong emergence of some insuper et supra high-level ontology). However,\nthe use of Dennett's criterion obscures this result, laying bare some philosophical issues,\nwhich we address over three axes of distinctions: (i) the objective/subjective-axis, (ii)\nthe quantitative/qualitative-axis within the framework of intertheoretic reduction and\n(iii) the ontological/epistemological-axis.\n\nFirst, Daniel Dennett's `real patterns' are compared to Wallace approach to patterns.\nThen, I point out (i) an analogy with Bas van Fraassen's idea of causal patterns\nthat become salient due to pragmatic explanation, namely that in the context of a pragmatic\ngoal the quasi-classical pattern is made salient over other objectively existing,\nnon-classical, patterns. I conclude that in the absence of human goals there is no reason\nto regard the quasi-classical pattern as `more real' than other patterns. In analogy to\nDennett's `intentional stance', Wallace is committed to a `classical stance', equivalent\nto breaking Hilbert space democracy of bases. \n\nAlthough Wallace's version is a weaker one, his (ii) relations between theories\nbare resemblance to the reductionist program, and I argue that, next to quantitative\ndeduction, additional conceptual `bridge principles' à la Ernest Nagel are needed.\nThe appeal to usefulness as a criterion for reality (iii), I claim, is not necessary\nto solve the measurement problem itself, but has the further (unwarranted) goal of\nestablishing `real' worlds. I spell out a solution to the measurement problem, the\nmany-minds theory, which solves the problem along the same lines as The Emergent\nMultiverse, with the exception that the - although the quantum world itself is real\n- the classical worlds with definite properties are beliefs in the superposed brains of\nobservers.
Dualities in physics have challenged traditional forms of scientific realism by undermining the idea that theories describe a unique underlying ontology. In this paper, we develop a new perspective on scientific realism that responds to this challenge. We argue that while realist commitment remains appropriate at the level of a theory's full formal structure, ontological commitment should be treated as tied to specific empirical contexts rather than to a fixed, real ontology. Our proposal draws inspiration from Dennett's notion of a "compression algorithm" as a defining criterion of a scientific theory. On this basis, we separate realism from ontological commitment. To clarify the stakes of this distinction, we contrast our approach with common core realism, which locates ontology in the invariant structure shared by dual models. Focusing on dualities in quantum mechanics and string theory, we show how our view accommodates ontological pluralism while preserving a robust form of structural realism.
In this paper we discuss the representational realist stance as a pluralist ontic approach to inter-theoretic relationships. Our stance stresses the fact that physical theories require the necessary consideration of a conceptual level of discourse which determines and configures the specific field of phenomena discussed by each particular theory. We will criticize the orthodox line of research which has grounded the analysis about QM in two (Bohrian) metaphysical presuppositions -accepted in the present as dogmas that all interpretations must follow. We will also examine how the orthodox project of "bridging the gap" between the quantum and the classical domains has constrained the possibilities of research, producing only a limited set of interpretational problems which only focus in the justification of "classical reality" and exclude the possibility of analyzing the possibilities of non-classical conceptual representations of QM. The representational realist stance introduces two new problems, namely, the superposition problem and the contextuality problem, which consider explicitly the conceptual representation of orthodox QM beyond the mere reference to mathematical structures and measurement outcomes. In the final part of the paper, we revisit, from a representational realist perspective, the quantum to classical limit and the orthodox claim that this inter-theoretic relation can be explained through the principle of decoherence.
In this paper we discuss the representational realist stance as a pluralist ontic approach to inter-theoretic relationships. Our stance stresses the fact that physical theories require the necessary consideration of a conceptual level of discourse which determines and configures the specific field of phenomena discussed by each particular theory. We will criticize the orthodox line of research which has grounded the analysis about QM in two (Bohrian) metaphysical presuppositions accepted in the present as dogmas that all interpretations must follow. We will also examine how the orthodox project of "bridging the gap" between the quantum and the classical domains has constrained the possibilities of research, producing only a limited set of interpretational problems which only focus in the justification of classical reality and exclude the possibility of analyzing the possibilities of non-classical conceptual representations of QM. The representational realist stance introduces two new problems, namely, the superposition problem and the contextuality problem, which consider explicitly the conceptual representation of orthodox QM beyond the mere reference to mathematical structures and measurement outcomes. In the final part of the paper, we revisit, from a representational realist perspective, the quantum to classical limit and the orthodox claim that this inter-theoretic relation can be explained through the principle of decoherence.
This article surveys a selection of key conceptual and interpretational developments in quantum mechanics, tracing the theory from its foundational postulates to contemporary discussions of measurement, nonlocality, and the emergence of classicality. Beginning with the structure of Hilbert space and the postulates governing state evolution and measurement, the epistemic stance of the Copenhagen interpretation and its modern reformulations are examined. The Einstein-Podolsky-Rosen argument, Bell's theorem, and Hardy's paradox are then discussed as probes of locality and realism, alongside the deterministic but explicitly nonlocal de Broglie-Bohm theory. The measurement problem and the implications of contextuality are analyzed in relation to objective collapse models, which introduce new physical dynamics to account for definite outcomes. Finally, the role of decoherence in the suppression of interference and the emergence of classical behavior is explored, together with the interpretational frameworks of many-worlds and consistent histories. This material aims to provide a coherent introductory overview of how several of the most prominent interpretations address the central concern of what quantum mechanics tells us about the nature of physical reality.