Quantum mechanics portrays the universe as involving non-local influences that are difficult to reconcile with relativity theory. By postulating backward causation, retro-causal interpretations of quantum mechanics could circumvent these influences and accordingly reconcile quantum mechanics with relativity. The postulation of backward causation poses various challenges for the retro-causal interpretations of quantum mechanics and for the existing conceptual frameworks for analyzing counterfactual dependence, causation and causal explanation. In this chapter, we analyze the nature of time, causation and explanation in a local, (...) deterministic retro-causal interpretation of quantum mechanics that is inspired by Bohmian mechanics. This interpretation of quantum mechanics offers a deterministic, local ‘hidden-variables’ model of the Einstein-Podolsky-Rosen experiment that poses a new challenge for Reichenbach’s principle of the common cause. In this model, the common cause – the state of particles at the emission from the source – screens off the correlation between its effects – the distant measurement outcomes – but nevertheless fails to explain the correlation between the effects. (shrink)

There exists a growing literature on the so-called physical Church-Turing thesis in a relativistic spacetime setting. The physical Church-Turing thesis is the conjecture that no computing device that is physically realizable can exceed the computational barriers of a Turing machine. By suggesting a concrete implementation of a beyond-Turing computer in a spacetime setting, Istvan Nemeti and Gyula David have shown how an appreciation of the physical Church-Turing thesis necessitates the confluence of mathematical, computational, physical, and indeed cosmological ideas. In this (...) essay, I will honour Istvan's seventieth birthday, as well as his longstanding interest in, and his seminal contributions to, this field going back to as early as 1987 by modestly proposing how the concrete implementation in Nemeti and D\'avid might be complemented by a quantum-information-theoretic communication protocol between the computing device and the logician who sets the beyond-Turing computer a task such as determining the consistency of Zermelo-Fraenkel set theory. This suggests that even the foundations of quantum theory and, ultimately, quantum gravity may play an important role in determining the validity of the physical Church-Turing thesis. (shrink)

J.S. Bell believed that his famous theorem entailed a deep and troubling conflict between the empirically verified predictions of quantum theory and the notion of local causality that is motivated by relativity theory. Yet many physicists continue to accept, usually on the reports of textbook writers and other commentators, that Bell’s own view was wrong, and that, in fact, the theorem only brings out a conflict with determinism or the hidden-variables program or realism or some other such principle that (unlike (...) local causality), allegedly, nobody should have believed anyway. Moreover, typically such beliefs arise without the person in question even being aware that the view they are accepting differs so radically from Bell’s own. Here we try to shed some light on the situation by focusing on the concept of local causality that is the heart of Bell’s theorem, and, in particular, by contrasting Bell’s own understanding with the analysis of Jon Jarrett which has been the most influential source, in recent decades, for the kinds of claims mentioned previously. We point out a crucial difference between Jarrett’s and Bell’s own understanding of Bell’s formulation of local causality, which turns out to be the basis for the erroneous claim, made by Jarrett and many others, that Bell misunderstood the implications of his own theorem. (shrink)

Most philosophers of physics are eliminativists about causation. Following Bertrand Russell’s lead, they think that causation is a folk concept that cannot be rationally reconstructed within a worldview informed by contemporary physics. Against this thesis, I argue that physics contributes to shaping the concept of causation, in two ways. 1. Special Relativity is a physical theory that expresses causal constraints. 2. The physical concept of a conserved quantity can be used in the functional reduction of the notion of causation. The (...) empirical part of this reduction makes the hypothesis that the transference of an amount of a conserved quantity is a necessary and sufficient condition for causation. This hypothesis is defended against several objections from physics: that amounts of energy do not possess the appropriate identity conditions required for being able to be transmitted, that there is no universal principle of the conservation of energy in General Relativity, and that there are at least two types of physical systems in which causation does not involve any transference: entangled systems in quantum mechanics and the Aharanov-Bohm effect. In order to show that physics provides means to elaborate the concept of causation it is important to avoid certain misunderstandings. In particular, the claim that there is causation in a physical world does not mean that causation is an additional ingredient of the "furniture" of the world, over and above the ingredients identified by physics. (shrink)

Most philosophers of physics are eliminativists about causation. Following Bertrand Russell’s lead, they think that causation is a folk concept that cannot be rationally reconstructed within a worldview informed by contemporary physics. Against this thesis, I argue that physics contributes to shaping the concept of causation, in two ways. (1) Special Relativity is a physical theory that expresses causal constraints. (2) The physical concept of a conserved quantity can be used in the functional reduction of the notion of causation. The (...) empirical part of this reduction makes the hypothesis that the transference of an amount of a conserved quantity is a necessary and sufficient condition for causation. This hypothesis is defended against several objections from physics: that amounts of energy do not possess the appropriate identity conditions required for being able to be transmitted, that there is no universal principle of the conservation of energy in General Relativity, and that there are at least two types of physical systems in which causation does not involve any transference: entangled systems in quantum mechanics and the Aharonov–Bohm effect. In order to show that physics provides means to elaborate the concept of causation it is important to avoid certain misunderstandings. In particular, the claim that there is causation in a physical world does not mean that causation is an additional ingredient of the “furniture” of the world, over and above the ingredients identified by physics. (shrink)

In previous works, an ontology of properties for quantum mechanics has been proposed, according to which quantum systems are bundles of properties with no principle of individuality. The aim of the present article is to show that, since quasi-set theory is particularly suited for dealing with aggregates of items that do not belong to the traditional category of individual, it supplies an adequate meta-language to speak of the proposed ontology of properties and its structure.

It is argued that while quantum mechanics contains nonlocal or entangled states, the instantaneous or nonlocal influences sometimes thought to be present due to violations of Bell inequalities in fact arise from mistaken attempts to apply classical concepts and introduce probabilities in a manner inconsistent with the Hilbert space structure of standard quantum mechanics. Instead, Einstein locality is a valid quantum principle: objective properties of individual quantum systems do not change when something is done to another noninteracting system. There is (...) no reason to suspect any conflict between quantum theory and special relativity. (shrink)

Experiments involving delayed-choice entanglement swapping seem to suggest that particles can become entangled after they’ve already been detected. This astonishing result is taken by some to undermine realism about entanglement. In this paper, I argue that one can offer a fully realist explanation of delayed-choice entanglement swapping by countenancing timelike entanglement relations. I argue that such an explanation—radical though it may be—isn’t incoherent and doesn’t invite paradox. I compare this approach to the antirealist alternative and a more deflationary realist strategy (...) defended by Egg, each of which face certain challenges. The upshot is that we should take seriously the possibility of timelike entanglement and seek to develop a framework for quantum theory which allows for it. (shrink)

The existence of natural laws, whether deterministic or indeterministic, and whether exceptionless or ceteris paribus, seems puzzling because it implies that mindless bits of matter behave in a consistent and co-ordinated way. I explain this puzzle by showing that a number of attempted solutions fail. The puzzle could be resolved if it were assumed that natural laws are a manifestation of God’s activity. This argument from natural law to God’s existence differs from its traditional counterparts in that, whereas the latter (...) seek to explain the fact of natural laws, the former seeks to explain their possibility. The customary objections to the traditional arguments cannot be successfully adapted to counter this new argument, with one exception which has only limited effect. I rebut four claims that the theistic solution to the puzzle about natural laws is paradoxical, though I concede that one of these claims has merit. I consider four objections to the new argument but find three of them more or less unsatisfactory. The fourth, if successful, would undermine our claims to know the truth about the world. (shrink)

According to the Gottesman–Knill theorem, quantum algorithms that utilize only the operations belonging to a certain restricted set are efficiently simulable classically. Since some of the operations in this set generate entangled states, it is commonly concluded that entanglement is insufficient to enable quantum computers to outperform classical computers. I argue in this article that this conclusion is misleading. First, the statement of the theorem is, on reflection, already evident when we consider Bell’s and related inequalities in the context of (...) a discussion of computational machines. This, in turn, helps us to understand that the appropriate conclusion to draw from the Gottesman–Knill theorem is not that entanglement is insufficient to enable a quantum performance advantage, but rather that if we limit ourselves to the operations referred to in the Gottesman–Knill theorem, we will not have used the resources provided by an entangled quantum system to their full potential. (shrink)

I argue that difference-making should be a crucial element for evaluating the quality of evidence for mechanisms, especially with respect to the robustness of mechanisms, and that it should take central stage when it comes to the general role played by mechanisms in establishing causal claims in medicine. The difference- making of mechanisms should provide additional compelling reasons to accept the gist of Russo-Williamson thesis and include mechanisms in the protocols for Evidence- Based Medicine, as the EBM+ research group has (...) been advocating. (shrink)

I discuss various formulations of stochastic Einstein locality (SEL), which is a version of the idea of relativistic causality, that is, the idea that influences propagate at most as fast as light. SEL is similar to Reichenbach's Principle of the Common Cause (PCC), and Bell's Local Causality. My main aim is to discuss formulations of SEL for a fixed background spacetime. I previously argued that SEL is violated by the outcome dependence shown by Bell correlations, both in quantum mechanics and (...) in quantum field theory. Here I reassess those verdicts in the light of some recent literature which argues that outcome dependence does not violate the PCC. I argue that the verdicts about SEL still stand. Finally, I briefly discuss how to formulate relativistic causality if there is no fixed background spacetime. (shrink)

In this paper we derive a theorem which proves that the physical interpretation implied by the first postulate of quantum mechanics is inconsistent with the orthodox formalism. In order to expose this inconsistency we will analyze how the concept of ‘physical system’ is built within classical theories through the notion of invariance and explain in what sense a vector in Hilbert space is not capable of fulfilling these same mathematical conditions. Through an analysis of the mathematical formalism we derive a (...) No Dynamical Invariance theorem which proves that, contrary to what is claimed in the first postulate, a vector in Hilbert space cannot be interpreted coherently as the state of a physical system. We conclude the paper by analyzing the consequences of the NDI theorem with respect to several ongoing debates in QM. (shrink)

In this paper we attempt to discuss what has Kochen-Specker theorem to say about physical invariance and quantum individuality. In particular, we will discuss the impossibility of making reference to objective physical properties within the orthodox formalism of quantum mechanics. Through an analysis of the meaning of physical invariance and quantum contextuality we will derive a Corollary to KS theorem that proves that a vector in Hilbert space cannot be interpreted coherently as an object possessing physical properties. As a consequence, (...) the notion of quantum object can be only defined in terms of nomological properties. We conclude the paper by analyzing the consequences of this Corollary to KS theorem for the ongoing debate about quantum individuality. (shrink)

Suppose one has a system, the infinite set of positive integers, P, and one wants to study the characteristics of a subset (or subsystem) of that system, the infinite subset of odd positives, O, relative to the overall system. In mathematics, this is done by pairing off each odd with a positive, using a function such as O=2P+1. This puts the odds in a one-to-one correspondence with the positives, thereby, showing that the subset of odds and the original set of (...) positives are the same size, or have the same cardinality. This counter-intuitive result ignores the “natural” relationship of one odd for every two positives in the sequence of positive integers, which would suggest that O is one-half the size of P. However, in the set of axioms that constitute mathematics, it is considered valid. Fair enough. In the physical universe (i.e., the starting system), though, relationships between entities matter. In biochemistry, if you start with an organism, say a rat, and you want to study its heart, you can do this by removing some heart cells and studying them in isolation in a cell culture system. But, the results often differ compared to what occurs in the intact animal because studying the isolated cultured cells ignores the relationships in the intact body between the cells, the rest of the heart tissue and the rest of the rat. In chemistry, if a copper atom were studied in isolation, it would never be known that copper atoms in bulk can conduct electricity because the atoms share their electrons. In physics, the relationships between inertial reference frames in relativity, and observer and observed in quantum physics can't be ignored. Relationships matter in the physical world, but the mathematics of infinite sets is still used to describe it. Does this matter? It seems to, at least in physics. Infinities cause numerous problems in theoretical physics such as non-renormalizability and problems in unifying quantum mehanics and general relativity . This suggests that the pairing off method and the mathematics of infinite sets based on it are analogous to a cell culture system or studying a copper atom in isolation if they are used in studying the physical universe because they ignore the inherent relationships between entities. In the real, physical world, the natural, inherent, relationships between entities can't be ignored. Said another way, the set of axioms that constitute abstract mathematics may be similar but not identical to the set of physical axioms by which the real, physical universe runs. This suggests that the results from abstract mathematics about infinities may not apply to or should be modified for use in physics. (shrink)

Mental causation between the material and the immaterial has been problematic for interactionist substance dualism ever since its first major proponent René Descartes. The contemporary philosopher Jaegwon Kim believes he has found an argument that shows exactly why an immaterial event cannot be said to cause a material event; he calls this the pairing problem argument. This thesis will argue that there is actually sufficient empirical evidence to suggest that Kim’s argument is unsuccessful due to one of its premises being (...) false. Furthermore, this thesis will also argue that interactionist substance dualism is actually a philosophically viable alternative, and lastly ways are sketched of how one might go about constructing such a view responsibly. (shrink)

Experiments demonstrating entanglement swapping have been alleged to challenge realism about entanglement. Seevinck claims that entangle- ment “cannot be considered ontologically robust” while Healey claims that entanglement swapping “undermines the idea that ascribing an entangled state to quantum systems is a way of representing some new, non-classical, physical relation between them.” My aim in this paper is to show that realism is not threatened by the possibility of entanglement swapping, but rather, it should be informed by the phenomenon. I argue—expanding (...) the argument of Timpson and Brown —that ordinary entanglement swapping cases present no new challenges for the realist. With respect to the delayed-choice variant discussed by Healey, I claim that there are two options available to the realist: deny these are cases of genuine swapping ) or allow for existence of entanglement between timelike separated regions. This latter option, while radical, is not incoherent and has been suggested in quite different contexts. While I stop short of claiming that the realist must take this option, doing so allows one to avoid certain costs associated with Egg’s “orthodox” account. I conclude by noting several important implication of entanglement swapping for how one thinks of entanglement generally. (shrink)

This paper develops a Fragmentalist theory of Presentism and shows how it can help to develop a interpretation of quantum mechanics. There are several fragmental interpretations of physics. In the interpretation of this paper, each quantum system forms a fragment, and fragment f1 makes a measurement on fragment f2 if and only if f2 makes a corresponding measurement on f1. The main idea is then that each fragment has its own present (or ‘now’) until a mutual quantum measurement—at which time (...) they come (‘become’) to share the same ‘now’. The theory of time developed here will make use of both McTaggart’s A-series (in the form of future-present-past) and B-series (earlier-times to later-times). An example of an application is that a Bell pair of electrons does not take on definite spin values until measurement because the measuring system and the Bell pair do not share the same present (‘now’) until mutual quantum measurement, i.e. until they ‘become’ to share the same A-series. Before that point the ‘now’ of the opposing system is not in the reference system’s fragment. Relativistic no-signaling is preserved within each fragment, which will turn out to be sufficient for the general case. Several issues in the foundations of quantum mechanics are canvassed, including Schrodinger’s cat, the Born rule, modifications to Minkowski space that accommodate both the A-series and the B-series, and entropy. (shrink)

This paper presents a novel theory of what it is that makes vision a representational affair. Vision is a process of representation; a fact that does not depend on it being "contentfull" or "indirect". Even if it turns out that vision is direct and/or intrinsically "contentless", it is nevertheless defined by features that decisively make it count as a process or representation. The phenomenology of vision is key here: as we see, we are directly presented with aspects of the environment (...) that are at various distances away from us. Through the process of vision, aspects of the environment that would otherwise still be unavailable or “absent”, are made (quasi-)available, or (quasi-)present. This already by itself makes vision deserving of the name ‘representational’, even if those distant aspects of the world are presented to us directly and contentless. In part I, I provide a bit of an overview of the relevant theoretical landscape, and I give my own take on how we may frame and approach some of the issues with respect to mental representation. Then, in part II, I argue that the representational features of vision must primarily be sought at the level of conscious experience. In part III, I elaborate on the two most common theories that are associated with the view that vision is ‘representational’, and proceed to show that there is in fact a third, more direct, way in which vision can be considered as essentially a process of representation. Finally, in part IV, I show that the kind of interaction problems that arise with the more traditional notions of representation also arise with this newer, more direct, notion. (shrink)

This commentary discusses the major claims and arguments presented by Field and Hineline (2008) against the general use of dispositional causal explanations in science and psychology and in favor of an alternative account that applies to cases in which causes and behavioral effects are separated over time. We conclude that their central claims and arguments are weak or implausible, and that the dispositional explanatory strategy emerges unscathed.

This white paper aims to identify an open problem in 'Quantum Physics and the Nature of Reality' -namely whether quantum theory and special relativity are formally compatible-, to indicate what the underlying issues are, and put forward ideas about how the problem might be addressed.