Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

Emergent Chance

Alastair Wilson

Published Feb 11, 2020• 0 citations
Publisher

Abstract

Abstract This chapter offers a theory of objective chance in the Everettian context, often seen as the main challenge facing EQM. By supplementing diverging EQM with quantum modal realist bridge principles connecting the physics of quantum mechanics with the metaphysics of modality, we obtain a package deal: Indexicalism. Indexicalist objective chance is an essentially self-locating phenomenon: chances are chances of self-location within the multiverse. I provide three arguments for Indexicalism: it establishes the right qualitative connections between chance and possibility, it establishes the right quantitative connection between chance and prediction, and it establishes the right epistemological story about how quantum mechanics is confirmed by empirical evidence. The resulting theory of chance is naturalistic and reductive; fundamental reality is deterministic, but chance arises at the non-fundamental level of Everett-worldbound perspectives. The theory provides unique resources for motivating an Everettian version of Lewis’s Principal Principle, helping to clarify at last the persistently mysterious connection between chance and rational credence.

DOI
10.1093/oso/9780198846215.003.0004

Related papers

Objective Probability in Everettian Quantum Mechanics

Alastair Wilson

David Wallace has given a decision-theoretic argument for the Born Rule in the context of Everettian quantum mechanics (EQM). This approach promises to resolve some long-standing problems with probability in EQM, but it has faced plenty of resistance. One kind of objection (the ‘incoherence problem’) charges that the requisite notion of decision-theoretic uncertainty is unavailable in the Everettian picture, so that the argument cannot gain any traction; another kind of objection grants the proof’s applicability and targets the premises. In this article I propose some novel principles connecting the physics of EQM with the metaphysics of modality, and argue that in the resulting framework the incoherence problem does not arise. These principles also help to justify one of the most controversial premises of Wallace’s argument, ‘branching indifference’. Absent any a priori reason to align the metaphysics with the physics in some other way, the proposed principles can be adopted on grounds of theoretical utility. The upshot is that Everettians can, after all, make clear sense of objective probability. 1 Introduction 2 Setup 3 Individualism versus Collectivism 4 The Ingredients of Indexicalism 5 Indexicalism and Incoherence 5.1 The trivialization problem 5.2 The uncertainty problem 6 Indexicalism and Branching Indifference 6.1 Introducing branching indifference 6.2 The pragmatic defence of branching indifference 6.3 The non-existence defence of branching indifference 6.4 The indexicalist defence of branching indifference 7 Conclusion

The British Journal for the Philosophy of Science•Oct 7, 2012•50 citations

Modal Metaphysics and the Everett Interpretation

Alastair Wilson

Recent work on probability in the Everett interpretation of quantum mechanics yields a decision-theoretic derivation of David Lewis’ Principal Principle, and hence a general metaphysical theory of probability; part 1 is a discussion of this remarkable result. I defend the claim that the ‘subjective uncertainty’ principle is required for the derivation to succeed, arguing that it amounts to a theoretical identification of chance. In part 2, I generalize this account, and suggest that the Everett interpretation, in combination with a plausible view of natural laws, has the potential to provide a reductive theory of metaphysical modality. I defend the resulting naturalistic modal realism, and outline some of its implications for other parts of metaphysics.

•Jan 1, 2006•3 citations

Credence and Chance in Quantum Theory

John Earman

David Lewis' "Principal Principle" is a purported principle of rationality connecting credence and objective chance. Almost all of the discussion of the Principal Principle in the philosophical literature assumes classical probability theory, which is unfortunate since the theory of modern physics that, arguably, speaks most clearly of objective chance is the quantum theory, and quantum probabilities are not classical probabilities. This paper develops an account of how chance works in quantum theory that reveals a connection between credence and quantum chance quite unlike what is envisioned in the philosophical literature: as a theorem of quantum probability, updating a completely additive chance function on a knowledge of chance brings credence into line with chance. The account also suggests a way of construing the Humean supervenience of chance that has the virtue of dissolving some puzzles about the "undermining" of chances. A number of interpretative moves in quantum theory are needed to generate the account of quantum chance on offer here, and they can all be disputed. But engaging in these disputes is part and parcel of naturalized metaphysics, and as such it can be more productive than engaging in the battle of intuitions among analytical metaphysicians about how chance ought to work this and other possible worlds.

•Sep 13, 2017•1 citation

Centered Chance in the Everett Interpretation

Jerome Romagosa

Everettian quantum mechanics tells us that the fundamental dynamics of the universe are deterministic. So what are the `probabilities' that the Born rule describes? One popular answer has been to treat these probabilities as rational credences. A recent alternative, Isaac Wilhelm's centered Everett Interpretation (CEI), takes the Born probabilities to be centered chances: the objective chances that some centered propositions are true. Thus, the CEI challenges the `orthodox assumption’ that fundamental physical laws concern only uncentered facts. I provide three arguments against the centered Everett Interpretation. First, I argue that the CEI is in apparent tension with a significant motivation for adopting Everettian quantum mechanics: rejecting the attribution of special significance to observers or agents in fundamental physics. I suggest the CEI can avoid this tension, but only at the cost of sacrificing its central claim that there are objective chances in an Everettian multiverse. My second argument concerns the CEI’s claim that the centered Born rule is a fundamental physical law. I provide two plausible notions of fundamentality for physical laws, and I argue that the centered Born rule satisfies neither. My final argument is that the CEI’s branch-relative laws cannot explain or constrain an agent’s rational credences in the way that the CEI claims.

The British Journal for the Philosophy of Science•Aug 22, 2024•0 citations

Indeterminacy

Alastair Wilson

Abstract In Everettian quantum mechanics, the universal quantum state is fundamental, non-contingent, and wholly determinate. By contrast, the parallel worlds of diverging EQM, and the contingency constituted by self-location amongst those worlds, are emergent and partly indeterminate. In particular, it is indeterminate both how many worlds there are, and what microscopic qualitative features those worlds have. This chapter discusses various ways to understand indeterminacy in the Everettian multiverse, and argues that the indeterminacies of EQM present no obstacle to the analytic ambitions of quantum modal realism. Everettians can understand quantum indeterminacy using models of indeterminacy that are familiar from the philosophical literature on vagueness.

•Feb 11, 2020•0 citations

Analysing Modality

Alastair Wilson

Abstract This chapter presents and defends the basic tenets of quantum modal realism. The first of these principles, Individualism, states that Everett worlds are metaphysically possible worlds. The converse of this principle, Generality, states that metaphysically possible worlds are Everett worlds. Combining Individualism and Generality yields Alignment, a conjecture about the nature of possible worlds that is closely analogous to Lewisian modal realism. Like Lewisian modal realism, Alignment entails that each possible world is a real concrete individual of the same basic kind as the actual world. These similarities render EQM suitable for grounding a novel theory of the nature of metaphysical modality with some unique properties. Also like Lewisian modal realism, quantum modal realism is a reductive theory: it accounts for modality in fundamentally non-modal terms. But quantum modal realism also has unique epistemological advantages over Lewisian modal realism and other extant realist approaches to modality.

•Feb 11, 2020•0 citations
Abstract This chapter offers a theory of objective chance in the Everettian context, often seen as the main challenge facing EQM. By supplementing diverging EQM with quantum modal realist bridge principles connecting the physics of quantum mechanics with the metaphysics of modality, we obtain a package deal: Indexicalism. Indexicalist objective chance is an essentially self-locating phenomenon: chances are chances of self-location within the multiverse. I provide three arguments for Indexicalism: it establishes the right qualitative connections between chance and possibility, it establishes the right quantitative connection between chance and prediction, and it establishes the right epistemological story about how quantum mechanics is confirmed by empirical evidence. The resulting theory of chance is naturalistic and reductive; fundamental reality is deterministic, but chance arises at the non-fundamental level of Everett-worldbound perspectives. The theory provides unique resources for motivating an Everettian version of Lewis’s Principal Principle, helping to clarify at last the persistently mysterious connection between chance and rational credence.
David Wallace has given a decision-theoretic argument for the Born Rule in the context of Everettian quantum mechanics (EQM). This approach promises to resolve some long-standing problems with probability in EQM, but it has faced plenty of resistance. One kind of objection (the ‘incoherence problem’) charges that the requisite notion of decision-theoretic uncertainty is unavailable in the Everettian picture, so that the argument cannot gain any traction; another kind of objection grants the proof’s applicability and targets the premises. In this article I propose some novel principles connecting the physics of EQM with the metaphysics of modality, and argue that in the resulting framework the incoherence problem does not arise. These principles also help to justify one of the most controversial premises of Wallace’s argument, ‘branching indifference’. Absent any a priori reason to align the metaphysics with the physics in some other way, the proposed principles can be adopted on grounds of theoretical utility. The upshot is that Everettians can, after all, make clear sense of objective probability. 1 Introduction 2 Setup 3 Individualism versus Collectivism 4 The Ingredients of Indexicalism 5 Indexicalism and Incoherence 5.1 The trivialization problem 5.2 The uncertainty problem 6 Indexicalism and Branching Indifference 6.1 Introducing branching indifference 6.2 The pragmatic defence of branching indifference 6.3 The non-existence defence of branching indifference 6.4 The indexicalist defence of branching indifference 7 Conclusion
Recent work on probability in the Everett interpretation of quantum mechanics yields a decision-theoretic derivation of David Lewis’ Principal Principle, and hence a general metaphysical theory of probability; part 1 is a discussion of this remarkable result. I defend the claim that the ‘subjective uncertainty’ principle is required for the derivation to succeed, arguing that it amounts to a theoretical identification of chance. In part 2, I generalize this account, and suggest that the Everett interpretation, in combination with a plausible view of natural laws, has the potential to provide a reductive theory of metaphysical modality. I defend the resulting naturalistic modal realism, and outline some of its implications for other parts of metaphysics.
David Lewis' "Principal Principle" is a purported principle of rationality connecting credence and objective chance. Almost all of the discussion of the Principal Principle in the philosophical literature assumes classical probability theory, which is unfortunate since the theory of modern physics that, arguably, speaks most clearly of objective chance is the quantum theory, and quantum probabilities are not classical probabilities. This paper develops an account of how chance works in quantum theory that reveals a connection between credence and quantum chance quite unlike what is envisioned in the philosophical literature: as a theorem of quantum probability, updating a completely additive chance function on a knowledge of chance brings credence into line with chance. The account also suggests a way of construing the Humean supervenience of chance that has the virtue of dissolving some puzzles about the "undermining" of chances. A number of interpretative moves in quantum theory are needed to generate the account of quantum chance on offer here, and they can all be disputed. But engaging in these disputes is part and parcel of naturalized metaphysics, and as such it can be more productive than engaging in the battle of intuitions among analytical metaphysicians about how chance ought to work this and other possible worlds.
Everettian quantum mechanics tells us that the fundamental dynamics of the universe are deterministic. So what are the `probabilities' that the Born rule describes? One popular answer has been to treat these probabilities as rational credences. A recent alternative, Isaac Wilhelm's centered Everett Interpretation (CEI), takes the Born probabilities to be centered chances: the objective chances that some centered propositions are true. Thus, the CEI challenges the `orthodox assumption’ that fundamental physical laws concern only uncentered facts. I provide three arguments against the centered Everett Interpretation. First, I argue that the CEI is in apparent tension with a significant motivation for adopting Everettian quantum mechanics: rejecting the attribution of special significance to observers or agents in fundamental physics. I suggest the CEI can avoid this tension, but only at the cost of sacrificing its central claim that there are objective chances in an Everettian multiverse. My second argument concerns the CEI’s claim that the centered Born rule is a fundamental physical law. I provide two plausible notions of fundamentality for physical laws, and I argue that the centered Born rule satisfies neither. My final argument is that the CEI’s branch-relative laws cannot explain or constrain an agent’s rational credences in the way that the CEI claims.
Abstract In Everettian quantum mechanics, the universal quantum state is fundamental, non-contingent, and wholly determinate. By contrast, the parallel worlds of diverging EQM, and the contingency constituted by self-location amongst those worlds, are emergent and partly indeterminate. In particular, it is indeterminate both how many worlds there are, and what microscopic qualitative features those worlds have. This chapter discusses various ways to understand indeterminacy in the Everettian multiverse, and argues that the indeterminacies of EQM present no obstacle to the analytic ambitions of quantum modal realism. Everettians can understand quantum indeterminacy using models of indeterminacy that are familiar from the philosophical literature on vagueness.
Abstract This chapter presents and defends the basic tenets of quantum modal realism. The first of these principles, Individualism, states that Everett worlds are metaphysically possible worlds. The converse of this principle, Generality, states that metaphysically possible worlds are Everett worlds. Combining Individualism and Generality yields Alignment, a conjecture about the nature of possible worlds that is closely analogous to Lewisian modal realism. Like Lewisian modal realism, Alignment entails that each possible world is a real concrete individual of the same basic kind as the actual world. These similarities render EQM suitable for grounding a novel theory of the nature of metaphysical modality with some unique properties. Also like Lewisian modal realism, quantum modal realism is a reductive theory: it accounts for modality in fundamentally non-modal terms. But quantum modal realism also has unique epistemological advantages over Lewisian modal realism and other extant realist approaches to modality.