In a reply to Nicholas Maxwell, Stein has proved that Minkowski spacetime can leave room for the kind of indeterminateness required both by certain interpretations of quantum mechanics and by objective becoming. By examining the consequences of outcome dependence in Bell-type experiments for the co-determinateness of spacelike-related events, I argue that the only becoming relation that is compatible with both causal and noncausal readings of the quantum correlations is the universal relation. This result might also undermine interpretations of quantum mechanics requiring non-epistemically indeterminate states before measurement and hyperplane-dependent wave collapse.
In a reply to Nicholas Maxwell, Stein has proved that Minkowski spacetime can leave room for the kind of indeterminateness required both by certain interpretations of quantum mechanics and by objective becoming. By examining the consequences of outcome dependence in Bell-type experiments for the co-determinateness of spacelike-related events, I argue that the only becoming relation that is compatible with both causal and noncausal readings of the quantum correlations is the universal relation. This result might also undermine interpretations of quantum mechanics requiring non-epistemically indeterminate states before measurement and hyperplane-dependent wave collapse.
As the previous chapter made clear, in the present interpretation quantum mechanics gives a rather specific account of EPR-type correlations and what underlies them. In the present chapter I argue that this account is genuinely explanatory (rather than merely an idle overlay on a simple description of the observed correlations), and that this constitutes a significant advantage of the present interpretation over certain rival interpretations, on which quantum mechanics is unable to offer an adequate explanation of the observed correlations. In order to make this argument it will prove necessary to examine the character of causal explanation in theoretical science, and in particular to develop a coherent metaphysics of a kind of holistic, nonseparable, causal explanation. I take the development of such a coherent metaphysics to constitute a significant task independent of the details of the present interpretation of quantum mechanics. Quantum mechanics is a mine of metaphysical insights, and I hope here at least to have exposed a rich seam. The first task is to defend the adequacy of the present account of EPR-type correlations as at least a coherent description of what may underlie the observed correlations. I foresee three main challenges to its descriptive adequacy. The first is to claim that the account is incompatible with the relativistic requirement that there can be no direct causal connection between spacelike-separated events, and must therefore be rejected. A weaker version of this challenge is to claim that although the incompatibility just mentioned may not by itself entail rejection of the account, it does seriously undermine its claim to be genuinely explanatory.
In quantum mechanics, quantum nonseparability is at the core of philosophical debates regarding its meaning. In the context of the process matrix formalism, causal nonseparability characterises quantum processes (connecting the inputs and outputs of different local quantum operations) that are incompatible with any definite causal structure among interacting parties. One talks about indefinite causal orders. A famous example of causally nonseparable processes is called the quantum switch (QS). It is extensively studied in the literature in virtue of its simple architecture and its various implementations in laboratories.The present work will discuss the possible interpretations of the QS's causal nonseparability under the assumption that causal nonseparability is seen as pointing towards novel objective features of nature.It was first defended that a scientific realist approach towards the process matrix formalism, which is an operational theory generalising quantum mechanics, was as much legitimate as any possible antirealist reading, contrary to certain views found in the literature. The reason is that operational formalisms are ontologically and epistemically neutral.From there, the theoretical concepts of interest, namely causal nonseparability and its model-independent counterpart called noncausality, were analysed in more details, in order to highlight in what sense they are distinct from the standard notions of quantum nonseparability and nonlocality in quantum mechanics.The discussion then focused on noncausality. It was argued that noncausality has a strong connection with a notion of temporal nonlocality. In the same way that Bell nonlocality is given different underlying explanations depending on the details of the chosen quantum mechanics' account, noncausality pointing towards temporal nonlocality can be given a variety of underlying descriptions depending on the exact way to interpret the process matrix formalism.The last chapter focused precisely on this particular point, namely on the various ways to understand process matrices and causal nonseparability in a realist context. In order to explore the potential impact of causal nonseparability on spacetime,we shifted from the notion of (indefinite) causal structure to (indefinite) spatiotemporal ones. This shift was allowed under a set of reasonable assumptions regarding the properties of a physical spacetime manifold and the connection between an operational and relativistic notions of causal relations.While different readings were suggested for indefiniteness of spatiotemporal relations, we insisted in particular on an objective understanding appealing to the concept of metaphysical indeterminacy. It was argued that such an approach could prove useful in a more general theoretical context such as quantum gravity, while being already partly supported in standard quantum mechanics.
In a recent paper, David Albert has suggested that no quantum theory can yield a description of the world unfolding in Minkowski spacetime. This conclusion is premature; a natural extension of Stein's notion of becoming in Minkowski spacetime to accommodate the demands of quantum nonseparability yields such an account, an account that is in accord with a proposal which was made by Aharonov and Albert but which is dismissed by Albert as a ‘mere trick’. The nature of such an account is clarified by an extension to a relativistic quantum context of David Lewis' picture of objective chances evolving in time. 1Introduction 2Classical relativistic becoming 3Relativistic quantum becoming, without collapse 4Relativistic quantum becoming, with collapse 5Objective chance, conditional probability, and definite properties 6The nature of the wave function 7Conclusion
We first examine Howard's analysis of the Bell factorizability condition in terms of ‘separability’ and ‘locality’ and then consider his claims that the violations of Bell's inequality by the statistical predictions of quantum mechanics should be interpreted in terms of ‘nonseparability’ rather than ‘nonlocality’ and that ‘nonseparability’ implies the failure of spacetime as a principle of individuation for quantum-mechanical systems. We will argue that his argument for the first claim is less than compelling and that any argument for the second claim will be interpretation-dependent and, hence, not generally valid.
Quantum entanglement confronts any realist account of temporal becoming with a precise challenge. If measurement on one member of an entangled pair determines the state of its distant partner, and if temporal becoming consists in the localised closure of possibility spaces along worldlines, then the correlations between spatially separated measurement outcomes appear to require either a privileged global simultaneity or a superluminal causal mechanism — both of which conflict with special relativity. This paper argues that Constraint Theory (CT) — the thesis, established by transcendental argument, that constraint is the ontological primitive constitutive of determinate existence as such — resolves this challenge by identifying the correct ontological level at which the entangled pair must be described. An entangled pair is not two distinct entities connected by an invisible thread; it is a single, non-separable constraint profile whose possibility space has not yet been closed into distinct token-level actualities. Measurement on one wing of the pair is a localised constraint-closure event that modifies the structure of the joint possibility space, leaving the remaining possibility space at the other wing structurally restricted. This structural restriction is not a causal signal propagating across space; it is a topological consequence of the non-separability of the joint profile itself. The account is consistent with special relativity, with the no-communication theorem, and with Bell’s theorem. It does not introduce hidden variables, does not require a preferred simultaneity frame, and does not invoke wave-function collapse as an ad hoc primitive. The paper situates the account relative to Everettian, Bohmian, GRW, relational, and QBist interpretations, and connects the entanglement account to the CT treatment of temporal becoming developed in the companion paper on time.
The dissertation is a defense of the following conditional claim: if there are objective collapses of the wavefunction, then the future is genuinely open. Although this is no radically new idea, the strategy I shall use to defend it is a new one. It proceeds in two main steps. First, building upon the recent literature on metaphysical indeterminacy in quantum mechanics, I argue for the view that systems in superposition have be interpreted as objectively indeterminate state of affairs. Second, I propose an alternative way to think of openness, according to which the future is open as of t, if and only if there is an indeterminate state of affair S at t, and S becomes determinate at t? (with t? later than t). To argue for the second step, I will give an analysis of the objective collapses of the wavefunction as the becoming determinate of previously indeterminate systems. Furthermore, in developing my arguments, I will also make some remarks concerning the ontology of objective collapse interpretations of quantum mechanics, the issue of whether metaphysical indeterminacy can be at some derivate level of reality, and the possibility of the openness of the future being an emergent phenomenon.