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Essay Review: David Wallace, The Emergent Multiverse

Guido Bacciagaluppi, Jenann Ismael

Published Jun 30, 2014• 1 citation
OpenAlex

Abstract

We review and discuss the recent monograph by David Wallace on Everettian Quantum Mechanics. This book is a high point of two decades of work on Everett in both physics and philosophy. It is also a beautiful and welcome exemplar of a modern way of doing metaphysics. We discuss certain aspects more critically, and take the opportunity to sketch an alternative pragmatist approach to probability in Everett, to be fully developed elsewhere.

Related papers

The Emergent Multiverse

David Wallace

Presenting a striking new account of the 'many worlds' approach to quantum theory, aka the Everett interpretation, David Wallace offers a clear and up-to-date survey of work on this theory in physics and in philosophy of science.

Oxford University Press eBooks•May 24, 2012•528 citations

Review of 'Many Worlds? Everett, Quantum Theory and Reality'

Jeremy Butterfield

This is a Critical Notice (published in 2011) for the general philosophical journal, Philosophy, of the anthology 'Many Worlds? Everett, Quantum Theory and Reality' (OUP), edited by Simon Saunders, Jonathan Barrett, Adrian Kent and David Wallace.

•Feb 1, 2011•1 citation

The Case for the Everett Multiverse

David Wallace

I give a non-technical presentation of the argument that quantum mechanics, in the form in which it is currently used, needs to be understood in many-worlds (Everettian) terms; the alternatives that have been discussed are at present not able to reproduce the full empirical content of the theory. This is a draft of a chapter for the forthcoming \emph{Blackwell Companion to Philosophy and the Multiverse (Klaas Kraay and Daniel Rubio, eds.) }

quant-pharXiv:2608.07706•Aug 11, 2026•0 citations

Incoherent? No, Just Decoherent: How Quantum Many Worlds Emerge

Alexander Franklin

Abstract The modern Everett interpretation of quantum mechanics describes an emergent multiverse. The goal of this paper is to provide a perspicuous characterisation of how the multiverse emerges making use of a recent account of (weak) ontological emergence. This will be cashed out with a case study that identifies decoherence as the mechanism for emergence. The greater metaphysical clarity enables the rebuttal of critiques due to Baker (2007) and Dawid and Thébault (2015) that cast the emergent multiverse ontology as incoherent; responses are also offered to challenges to the Everettian approach from Maudlin (2010) and Monton (2013).

arXiv:2501.16020•Philosophy of Science•Oct 19, 2023•8 citations

Worldly Patterns: Emergence, Functionalism and Pragmatic Reality

Ruward A. Mulder

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.

•Jan 1, 2018•0 citations

The Many Worlds Interpretation of QM

Robert Charles Koons

A group of philosophers and physicists at Oxford have recently crafted, in light of developments in the theory of decoherence, a new version of the Everett or Many Worlds interpretation of quantum mechanics. I will focus on the work of David Wallace, who identifies the quasi-classical domains making up the various “worlds” or “branches” of the interpretation with macroscopic patterns that are functionally realized (to an approximate degree good enough for practical purposes) by the quantum wavefunction of the universe. I argue that Wallace’s reliance on Savage’s pragmatic account of probability fails, due to the unreasonableness of Savage’s Sure Thing Principle in a many-worlds setting. I also argue that Wallace’s program is vulnerable to a version of Putnam’s model-theoretic indeterminacy argument, with the result that almost any conceivable macroscopic “world” is in fact realized by that function and so is (by Wallace’s light) as real as our own. I offer a hylomorphic revision of the many-worlds model, the “traveling forms” interpretation of Alexander Pruss, and I argue that this revision solves both the indeterminacy problem and the problem of interpreting quantum probabilities.

Routledge eBooks•Oct 19, 2017•8 citations
We review and discuss the recent monograph by David Wallace on Everettian Quantum Mechanics. This book is a high point of two decades of work on Everett in both physics and philosophy. It is also a beautiful and welcome exemplar of a modern way of doing metaphysics. We discuss certain aspects more critically, and take the opportunity to sketch an alternative pragmatist approach to probability in Everett, to be fully developed elsewhere.
Abstract The modern Everett interpretation of quantum mechanics describes an emergent multiverse. The goal of this paper is to provide a perspicuous characterisation of how the multiverse emerges making use of a recent account of (weak) ontological emergence. This will be cashed out with a case study that identifies decoherence as the mechanism for emergence. The greater metaphysical clarity enables the rebuttal of critiques due to Baker (2007) and Dawid and Thébault (2015) that cast the emergent multiverse ontology as incoherent; responses are also offered to challenges to the Everettian approach from Maudlin (2010) and Monton (2013).
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.
A group of philosophers and physicists at Oxford have recently crafted, in light of developments in the theory of decoherence, a new version of the Everett or Many Worlds interpretation of quantum mechanics. I will focus on the work of David Wallace, who identifies the quasi-classical domains making up the various “worlds” or “branches” of the interpretation with macroscopic patterns that are functionally realized (to an approximate degree good enough for practical purposes) by the quantum wavefunction of the universe. I argue that Wallace’s reliance on Savage’s pragmatic account of probability fails, due to the unreasonableness of Savage’s Sure Thing Principle in a many-worlds setting. I also argue that Wallace’s program is vulnerable to a version of Putnam’s model-theoretic indeterminacy argument, with the result that almost any conceivable macroscopic “world” is in fact realized by that function and so is (by Wallace’s light) as real as our own. I offer a hylomorphic revision of the many-worlds model, the “traveling forms” interpretation of Alexander Pruss, and I argue that this revision solves both the indeterminacy problem and the problem of interpreting quantum probabilities.