Cet ouvrage pose la question de la construction de sens au cours de religion catholique de Belgique francophone, avec une proposition qui concerne plus particulièrement les élèves de la fin du secondaire et leurs enseignant·es. Trois fils rouges guident le travail, qui lui confèrent une coloration spécifique. Le premier a trait au sens, entendu dans son acception la plus large, qui va du sens du langage au sens le plus ultime, en passant par le sens tel qu'il se décline au (...) coeur d’une existence. Le suivant renvoie à l’articulation entre la construction et la transmission d’un sens, la première expression se rapportant à la pratique des communautés de recherche, la seconde s’inscrivant dans l’acception classique du terme en lien aux savoirs. Le dernier fil conducteur est relatif à l’association de deux disciplines essentielles pour le cours: la philosophie et la théologie, avec une insistance sur la philosophie comme mode de vie et quête de sagesse, à rapprocher de la quête de sens, mais également sur l’intérêt d’introduire les jeunes à une forme de silence et d’introspection. (shrink)

We study the EPR-type correlations from the perspective of the relational interpretation of quantum mechanics. We argue that these correlations do not entail any form of “non-locality”, when viewed in the context of this interpretation. The abandonment of strict Einstein realism implied by the relational stance permits to reconcile quantum mechanics, completeness, (operationally defined) separability, and locality.

We give a conceptually simple proof of nonlocality using only the perfect correlations between results of measurements on distant systems discussed by Einstein, Podolsky and Rosen—correlations that EPR thought proved the incompleteness of quantum mechanics. Our argument relies on an extension of EPR by Schrödinger. We also briefly discuss nonlocality and “hidden variables” within Bohmian mechanics.

A mathematical rigorous definition of EPR states has been introduced by Arens and Varadarajan for finite dimensional systems, and extended by Werner to general systems. In the present paper we follow a definition of EPR states due to Werner. Then we show that an EPR state for incommensurable pairs is Bell correlated, and that the set of EPR states for incommensurable pairs is norm dense between two strictly space-like separated regions in algebraic quantum field theory.

Bohr’s reply to Einstein, Podolsky, and Rosen’s argument for the incompleteness of quantum theory is notoriously difficult to unravel. It is so diffcult, in fact, that over 60 years later, there remains important work to be done understanding it. Work by Fine , Beller and Fine , and Beller goes a long way towards correcting earlier misunderstandings of Bohr’s reply. This essay is intended as a contribution to the program of getting to the truth of the matter, both historically and (...) philosophically. In a paper of this length, a full account of Bohr’s reply is impossible, and so I shall focus on one issue where it seems further clarification is required, namely, Bohr’s attempt to illustrate EPR’s argument by means of a thought experiment. In addition, I shall attempt to clarify a few other points which, however minor, have apparently contributed to misunderstandings of Bohr’s position. As the title of this paper suggests, an account of these few points does not constitute an account of Bohr’s reply, but it is an important step in that direction. (shrink)

As part of the creation-discovery interpretation of quantum mechanics Diederik Aerts presented a setting with macroscopical coincidence experiments designed to exhibit significant conceptual analogies between portions of stuff and quantum compound entities in a singlet state in Einstein—Podolsky—Rosen/Bell-experiments (EPR-experiments). One important claim of the creation-discovery view is that the singlet state describes an entity that does not have a definite position in space and thus does not exist in space. Free Process Theory is a recent proposal by Johanna Seibt of (...) an integrated ontology, i.e., of an ontology suitable for the interpretation of theories of the macrophysical and microphysical domain (quantum field theory). The framework of free process theory allows us to show systematically the relevant analogies and disanalogies between Aerts' experiment and EPR-experiments. From free process ontology it also follows quite naturally that the quantum compound entity described by the singlet state does not exist in space. (shrink)

Contemporary empiricism is closely allied with naturalism. Not only do empiricists hold that all our knowledge is based upon sensory experience, but they also tend to offer some sort of causal account of how this experience comes about. The causal ingredient in knowledge seems very plausible — after all, my knowing that there is a tea cup on my desk is based on sense impressions which are caused by the cup itself. Photons come from the cup to my eye; a (...) signal is then sent down the optic nerve into the visual part of the brain, and so on. And without that causal process, I likely wouldn't have the knowledge that I do have. (shrink)

Two EPR arguments are reviewed, for their own sake, and for the purpose of clarifying the status of "stochastic" hidden variables. The first is a streamlined version of the EPR argument for the incompleteness of quantum mechanics. The role of an anti-instrumentalist ("realist") interpretation of certain probability statements is emphasized. The second traces out one horn of a central foundational dilemma, the collapse dilemma; complex modal reasoning, similar to the original EPR, is used to derive determinateness (of all spin components (...) of two spin- 1 / 2 particles in the singlet state) from just (a form of) weak locality, result definiteness, and an assumption on propensities based on conservation. Theories meeting these conditions are therefore constrained by the Bell inequalities. Neither controversial assumptions of "strong locality" ("factorability") nor of determinism are employed in the derivation. The categories of "stochastic hidden variables" are then analyzed; one can focus on "quasi-definite" theories, without loss of generality. A means of excluding these is proposed, based on a demand that certain ideal cases be accurately treated. Theorems from quantum measurement theory, sometimes cited as showing that such cases are not physically possible, are found inapplicable. (shrink)

Delayed-choice erasure is investigated in two-photon two-slit experiments that are generalizations of the micromaser experiment of Scully et al. (Nature 351:111–116, 1991). Applying quantum mechanics to the localization detector, it is shown that erasure with delayed choice in the sense of Scully, has an analogous structure as simple erasure. The description goes beyond probabilities. The EPR-type disentanglement, consisting in two mutually incompatible distant measurements, is used as a general framework in both parts of this study. Two simple coherence cases are (...) shown to emerge naturally, and they are precisely the two experiments of Scully et al. The treatment seems to require the relative-reality-of-unitarily-evolving-state (RRUES) approach. Besides insight in the experiments, this study has also the goal of insight in quantum mechanics. The question is if the latter can be more than just a “book-keeping device” for calculating probabilities as Scully et al. modestly and cautiously claim. (shrink)

It was pointed out in the first part of this study (Herbut in Found. Phys. 38:1046–1064, 2008) that EPR-type entanglement is defined by the possibility of performing any of two mutually incompatible distant, i.e., direct-interaction-free, measurements. They go together under the term ‘EPR-type disentanglement’. In this second part, quantum-mechanical insight is gained in the real random delayed-choice erasure experiment of Kim et al. (Phys. Rev. Lett. 84:1–5, 2000) by a relative-reality-of-unitarily-evolving-state (RRUES) approach (explained in the first part). Finally, it is (...) shown that this remarkable experiment, which performs, by random choice, two incompatible measurements at the same time, is actually an EPR-type disentanglement experiment, closely related to the micromaser experiment discussed in the first part. (shrink)

Last June I was an invited speaker at the symposium “Frontiers of Time: Reverse Causation—Experiment and Theory,” part of a meeting of the American Association for the Advancement of Science (AAAS) held on the beautiful campus of the University of San Diego. (Here, reverse causation means a violation of that most mysterious law of physics, the Principle of Causality, which requires that any cause must precede its effects in all reference frames.) I had originally intended to just talk about my (...) work on the transactional interpretation of quantum mechanics and its somewhat retrocausal aspects (i.e., back-in-time handshakes of quantum waves, etc.). However, a new idea involving signaling with nonlocal quantum processes had come my way, and I decided to present it as a retrocausal quantum paradox at the symposium. It made a big splash there, but none of the experts present could identify any problem with the proposed thought experiment or resolve the paradox. In this column I want to tell you about this causality-violating communications scheme and its possible consequences. (shrink)

This paper is a critical discussion of a recent article by Bas van Fraassen in which he suggests the following view: we should admit that we have no explanation of the EPR correlations, but refuse to consider the correlations as mysterious nevertheless. We shall focus on just three of the claims made by van Fraassen in support of this view. The three claims are these:The EPR correlations cannot be explained by signals being transmitted from one component of an EPR compound (...) to the other.There is, in the EPR situation, no empirically verifiable action at a distance.The demand for an explanation of the EPR correlations is similar to the Aristotelian demand of the post-Newtonian proponents of the law of inertia to explain what keeps a body moving if there are no forces impressed on it. (shrink)

The essay revisits the puzzle of the ‘passage’ of time in relation to EPR-type measurements and asks what philosophical consequences can be drawn from them. Some argue that the lack of invariance of temporal order in the measurement of a space-like related EPR pair, under relativistic motion, casts serious doubts on the ‘reality’ of the lapse of time. Others argue thatcertain features of quantum mechanics establisha tensed theory of time – understood here as Possibilism or the growing block universe. The (...) paper analyzes the employment of frame-invariant entropic clocks in a relativistic setting and argues that tenselessness does not imply timelessness. But this conclusion does not support a tensed theory of time, which requires a preferred foliation. It is argued that the only reliable inference from the EPR example and the use of entropic clocks is an inference not just to a Leibnizian order of the succession of events but a frame-invariant order according to some selected clocks. (shrink)

The paradoxes of the EPR experiment with two particles are shown to originate in the implicit assumption that the particles are always located in the classical space. There exists a substitute for this assumption that yields a new definition of reality and offers a resolution of the paradoxes.

This paper takes up Huw Price׳s challenge to develop a retrocausal toy model of the Bell-EPR experiment. I develop three such models which show that a consistent, local, hidden-variables interpretation of the EPR experiment is indeed possible, and which give a feel for the kind of retrocausation involved. The first of the models also makes clear a problematic feature of retrocausation: it seems that we cannot interpret the hidden elements of reality in a retrocausal model as possessing determinate dispositions to (...) affect the outcome of experiments. This is a feature which Price has embraced, but Gordon Belot has argued that this feature renders retrocausal interpretations “unsuitable for formal development”, and the lack of such determinate dispositions threatens to undermine the motivation for hidden-variables interpretations in the first place. But Price and Belot are both too quick in their assessment. I show that determinate dispositions are indeed consistent with retrocausation. What is more, I show that the ontological economy allowed by retrocausation holds out the promise of a classical understanding of spin and polarization. (shrink)

I show that locality, as it occurs in EPR arguments for the incompleteness of quantum mechanics, can be construed as causal independence understood in terms of Lewis' counterfactual analysis of causation. This construal has two benefits. It supplements recent analyses, which have not treated locality in detail. And it clarifies the relation between two EPR arguments that have recently been distinguished. It shows that the simpler of the two is more complex than has been thought; and that the other argument (...) does not need 'counterfactual definiteness'. (shrink)

"Indeed I have very little idea of what this means. I do not understand in what sense the word `mechanical' is used, in characterizing the disturbances that Bohr does not contemplate, as distinct from those he does. I do not know what the italicized passage means--- `an influence on the very conditions...' . Could it mean just that different experiments on the first system give different kinds of information about the second? But this was one of the main points of (...) EPR, who observed that one could learn *either* the position *or* the momentum of the second system..... Is Bohr just rejecting the premise--- `no action at a distance'---rather than refuting the argument?". (shrink)

Recent studies have shown that Einstein did not write the EPR paper and that he was disappointed with the outcome. He thought, rightly, that his own argument for the incompleteness of quantum theory was badly presented in the paper. We reconstruct the argument of EPR, indicate the reasons Einstein was dissatisfied with it, and discuss Einstein's own argument. We show that many commentators have been misled by the obscurity of EPR into proposing interpretations of its argument that do not accurately (...) represent Einstein's own views. Finally, we evaluate Einstein's own incompleteness argument, concluding that recent experimental findings have likely shown it to be unsound. (shrink)

In this paper we discuss expected and reported effects on care provider-patient relations of the introduction of electronic patient records (EPRs) in consultation settings by reviewing exemplary studies and literature on the subject from the past decade. We argue that in order for such assessments to be meaningful, talk of effects of “the” EPR needs to be replaced by an “unpacking” of EPR systems into their constituent parts and functionalities, the effects of which need to be assessed individually. Following from (...) this principle, the paper discusses EPR systems ranging from simple data entry and retrieval systems to more sophisticated multi-user and multifunctional on-line systems. On a second level, our analysis of the literature is informed by the question which model of ideal patienthood underlies the assessment of effects of EPRs. To this end, we identify three “models of patienthood” implicit in writing about benefits and drawbacks of EPRs for patients: the autonomy, the consumer, and the holistic models, and argue that assumptions concerning these models need to be reflected upon more critically to improve understanding of what exactly EPR use does to the doctor-patient relationship. (shrink)

Dividing, Separating and Unifying. EPR Without Holism. In the standard interpretation of quantum mechanics parts of composed systems are correlated in a non-causal way, they are ontologically dependent on each other. In this paper I try to defend traditional realism giving a non-holistic interpretation of the EPR-paradox. An analysis of events in the macroscopic world shows that dividing and unifying objects is quite dif-ferent from changing (modifying) objects. In application to quantum mechanics I argue that a measurement at a given (...) single-system changes (modifies) this object, but the EPR-measurement divides the given object. Therefore this given object is an undivided and dividable One and not a composed system. If parts are produced (by EPR-measurement) correlations do not occur. (shrink)

There is no EPR-like funny business if (contrary to apparent fact)our world is as indeterministic as you wish, but is free from theEPR-like quantum mechanical phenomena such as is sometimes described interms of superluminal causation or correlation between distant events.The theory of branching space-times can be used to sharpen thetheoretical dichotomy between EPR-like funny business and noEPR-like funny business. Belnap (2002) offered two analyses of thedichotomy, and proved them equivalent. This essay adds two more, bothconnected with Reichenbachs principle of the (...) common cause, theprinciple that sends us hunting for a common-causal explanation ofdistant correlations. The two previous ideas of funny business and thetwo ideas introduced in this essay are proved to be all equivalent,which increases ones confidence in the stability of (and helpfulnessof) the BST analysis of the dichotomy between EPR-like funny businessand its absence. (shrink)

In 1935, Einstein, Podolsky and Rosen famously published a paper arguing for the incompleteness of quantum mechanics, using the example of two spatially separated but entangled particles. In his almost equally famous reply, Niels Bohr argued against EPR by providing a careful analysis of quantum measurements from the point of view of complementarity. Perhaps oddly, this analysis focuses on the example of a *single* particle passing through a slit. In this paper I argue that the disanalogy between the two examples (...) is only apparent, and does not constitute an obstacle in trying to understand Bohr's views on complementarity. (shrink)

It is still a matter of controversy whether the Principle of the Common Cause can be used as a basis for sound causal inference. It is thus to be expected that its application to quantum mechanics should be a correspondingly controversial issue. Indeed the early 90’s saw a flurry of papers addressing just this issue in connection with the EPR correlations. Yet, that debate does not seem to have caught up with the most recent literature on causal inference generally, which (...) has moved on to consider the virtues of a generalised PCC inspired condition, the so called Causal Markov Condition. In this paper we argue that the CMC is an appropriate benchmark for debating possible causal explanations of the EPR correlations. But we go on to take issue with some pronouncements on EPR by defenders of the CMC. (shrink)

We perform a frequency analysis of the EPR-Bell argumentation. One of the main consequences of our investigation is that the existence of probability distributions of the Kolmogorov-type which was supposed by some authors is a mathematical assumption which may not be supported by actual physical quantum processes. In fact, frequencies for hidden variables for quantum particles and measurement devices may fluctuate from run to run of an experiment. These fluctuations of frequencies for micro-parameters need not contradict to the stabilization of (...) frequencies for physical observables. If, nevertheless, micro-parameters are also statistically stable, then violations of Bell's inequality and its generalizations may be a consequence of dependence of collectives corresponding to two different measurement devices. Such a dependence implies the violation of the factorization rule for the simultaneous probability distribution. Formally this rule coincides with the well known BCHS locality condition (or outcome independence condition). However, the frequency approach implies totally different interpretation of dependence. It is not dependence of events, but it is dependence of collectives. Such a dependence may be induced by the same preparation procedure. (shrink)

The paper argues that on three out of eight possible hypotheses about the EPR experiment we can construct novel and realistic decision problems on which (a) Causal Decision Theory and Evidential Decision Theory conflict (b) Causal Decision Theory and the EPR statistics conflict. We infer that anyone who fully accepts any of these three hypotheses has strong reasons to reject Causal Decision Theory. Finally, we extend the original construction to show that anyone who gives any of the three hypotheses any (...) non-zero credence has strong reasons to reject Causal Decision Theory. However, we concede that no version of the Many Worlds Interpretation (Vaidman, in Zalta, E.N. (ed.), Stanford Encyclopaedia of Philosophy 2014) gives rise to the conflicts that we point out. (shrink)

The main idea of quantum mechanics, whether formulated in terms of the Planck constant or the noncommutativity of certain observables, must be tied to the recognition of the relativity and nonuniversality of the abstract concept of set (manifold) in the description of quantum systems. This entails the necessarily probabilistic description of quantum systems: since a quantum system ultimately cannot be decomposed into elements or sets, we have to describe it in terms of probabilities of only a relative selection of certain (...) elements or sets in its structure. This gives rise to the potential possibilities of quantum systems in an actual physical situation, and as a result the corresponding probabilities are ontologically real, like any other physically verifiable relationships. In this way, the quantum potential possibilities (and probabilities as their measure) are no less objectively real than the conventional reality which we identify with the physically directly verifiable elements, particles, etc. Indeed, the distribution of probabilities described by the nonfactorizable wave function is as objectively real and concrete as chairs, walls and all other physical things. In the pure quantum state the probabilities of selection of elements from the ultimately detailed state of the system are mutually coordinated and correlated by the phenomenon of wholeness of the system, and form an implicative logical structure governed by this phenomenon of wholeness. This idea of the implicative logical organization of the probabilistic structure of a quantum system in the so-called pure (non-detailable) state, and the governing role of the phenomenon of wholeness (in the redistribution of probabilities depending on the nature of the development of the real experiment), is in good agreement with the results of quantum correlation experiments (for example, the experiments of Alain Aspect, Nicolas Gisin and others). (shrink)

The main idea of quantum mechanics, whether formulated in terms of the Planck constant or the noncommutativity of certain observables, must be tied to the recognition of the relativity and nonuniversality of the abstract concept of set (manifold) in the description of quantum systems. This entails the necessarily probabilistic description of quantum systems: since a quantum system ultimately cannot be decomposed into elements or sets, we have to describe it in terms of probabilities of only a relative selection of certain (...) elements or sets in its structure. This gives rise to the potential possibilities of quantum systems in an actual physical situation, and as a result the corresponding probabilities are ontologically real, like any other physically verifiable relationships. In this way, the quantum potential possibilities (and probabilities as their measure) are no less objectively real than the conventional reality which we identify with the physically directly verifiable elements, particles, etc. Indeed, the distribution of probabilities described by the nonfactorizable wave function is as objectively real and concrete as chairs, walls and all other physical things. In the pure quantum state the probabilities of selection of elements from the ultimately detailed state of the system are mutually coordinated and correlated by the phenomenon of wholeness of the system, and form an implicative logical structure governed by this phenomenon of wholeness. This idea of the implicative logical organization of the probabilistic structure of a quantum system in the so-called pure (non-detailable) state, and the governing role of the phenomenon of wholeness (in the redistribution of probabilities depending on the nature of the development of the real experiment), is in good agreement with the results of quantum correlation experiments (for example, the experiments of Alain Aspect, Nicolas Gisin and others). (shrink)

The best case for thinking that quantum mechanics is nonlocal rests on Bell's Theorem, and later results of the same kind. However, the correlations characteristic of Einstein–Podolsky–Rosen (EPR)–Bell (EPRB) experiments also arise in familiar cases elsewhere in quantum mechanics (QM), where the two measurements involved are timelike rather than spacelike separated; and in which the correlations are usually assumed to have a local causal explanation, requiring no action-at-a-distance (AAD). It is interesting to ask how this is possible, in the light (...) of Bell's Theorem. We investigate this question, and present two options. Either (i) the new cases are nonlocal too, in which case AAD is more widespread in QM than has previously been appreciated (and does not depend on entanglement, as usually construed); or (ii) the means of avoiding AAD in the new cases extends in a natural way to EPRB, removing AAD in these cases too. There is a third option, viz., that the new cases are strongly disanalogous to EPRB. But this option requires an argument, so far missing, that the physical world breaks the symmetries which otherwise support the analogy. In the absence of such an argument, the orthodox combination of views—action-at-a-distance in EPRB, but local causality in its timelike analogue—is less well established than it is usually assumed to be. 1 Introduction1.1 Background1.2 Outline of the argument2 The Experiments2.1 Standard EPRB2.2 Sideways EPRB2.3 Comparing the experiments2.4 The need for beables3 The Symmetry Considerations3.1 The action symmetry3.2 Time-symmetry in SEPRB4 The Basic Trilemma4.1 An intuitive defence of Option III?5 Avoiding the Trilemma?6 The Classical Objection7 Defending Option III7.1 The free will argument7.2 Independence and consistency8 Entanglement and Epistemic Perspective. (shrink)

A generalized reality criterion which attributes physical properties to statistical ensembles is used in order to deduce an inequality which is violated by quantum mechanics in realistic conditions. This new form of the Einstein-Podolsky-Rosen paradox is developed exclusively from the reality criterion and from separability without any use of the previously introduced restrictive assumptions about the probabilistic scheme.

I show that locality, as it occurs in EPR arguments for the incompleteness of quantum mechanics, can be construed as causal independence understood in terms of Lewis’ counterfactual analysis of causation. This construal has two benefits. It supplements recent analyses, which have not treated locality in detail. And it clarifies the relation between two EPR arguments that have recently been distinguished. It shows that the simpler of the two is more complex than has been thought; and that the other argument (...) does not need ‘counterfactual definiteness’.I aim to show that in the EPR argument (Einstein et al. 1935) for the incompleteness of quantum mechanics (QM), locality can be taken as causal independence, understood in terms of Lewis’ counterfactual analysis of causation.Recent analyses of the EPR argument makes this construal of locality timely, for two reasons. First, these analyses typically say little about locality. (shrink)

We prove that the general scheme for physical theories that we have called semantic realism(SR) in some previous papers copes successfully with a number of EPR-like paradoxes when applied to quantum physics (QP). In particular, we consider the old arguments by Furry and Bohm- Aharonov and show that they are not valid within a SR framework. Moreover, we consider the Bell-Kochen-Specker und the Bell theorems that should prove that QP is inherently contextual and nonlocal, respectively, and show that they can (...) be invalidated in the SR approach. This removes the seeming contradiction between the basic assumptions of SR and QP, and proves that some problematic features that are usually attributed to QP, us contextuality and nonlocality, occur because of the adoption of a verificationist position, from one side, and from an insufficient adherence to the operational principles that have inspired QP itself, from the other side. (shrink)

This page contains references to the key original papers on the longstanding debate about the completeness of Quantum Mechanics (QM), particularly Bell's Theorem. It is not intended to be a definitive collection or exposition on the matter. Quite the opposite, it is limited to the 3 essential papers in the series, which were written over a nearly 50 year time span. These amazing papers lay out a complex line of reasoning involving our fundamental understanding of reality in the physical sense. (...) Each is brilliant and ground-breaking in its own right, building to a powerful conclusion regarding the matter. (shrink)

We present an exegesis of the Einstein-Podolsky-Rosen argument for the incompleteness of quantum mechanics, and defend it against the critique in Fine. (1) We contend,contra Fine, that it compares favorably with an argument reconstructed by him from a letter by Einstein to Schrödinger; and also with one given by Einstein in a letter to Popper. All three arguments turn on a dubious assumption of “separability,” which accords separate elements of reality to space-like separated systems. We discuss how this assumption figures (...) in the literature spawned by the Bell inequalities. (shrink)

For many years after Bohr's response to the EPR argument, Bohr was considered to have provided an authoritative rebuttal of the ideas of the paper, and more generally of Einstein's stance on quantum theory. More recently, however, there has been great difficulty even in achieving general agreement on Bohr's meaning. Two recent papers, by Dickson, and by Clifton and Halvorson, have sought to establish the structure of Bohr's argument. In the present paper, the papers of EPR and Bohr are re-assessed (...) in the light of these recent papers, and also in light of the development and presentation of quantum information theory. (shrink)

The paper investigates, in the framework of branching space–times, whether an infinite EPR-like correlation which does not involve finite EPR-like correlations is possible.

We study Bell inequalities and EPR states in the context of Jordan algebras. We show that the set of states violating Bell inequalities across two operator commuting nonmodular Jordan Banach algebras is norm dense in the global state space. It generalizes hitherto known results in quantum field theory in several directions. We propose new Jordan quantity for incommensurable observables in a given state, introduce the concept of EPR state for Jordan structures, and study relationship between EPR states and Bell correlated (...) states. Our analysis shows crucial role of spin factors and Pauli spin matrices for studying noncommutative properties of states and observables. (shrink)

An eight parameter family of the most general nonnegative quadruple probabilities is constructed for EPR-Bohm-Aharonov experiments when only 3 pairs of analyser settings are used. It is a simultaneous representation of 3 Bohr-incompatible experimental configurations valid for arbitrary quantum states.

I present a very general and simple argument—based on the no-signalling theorem—showing that within the framework of the unitary Schrödinger equation it is impossible to reproduce the phenomenological description of quantum mechanical measurements (in particular the collapse of the state of the measured system) by assuming a suitable mixed initial state of the apparatus. The thrust of the argument is thus similar to that of the ‘insolubility theorems’ for the measurement problem of quantum mechanics (which, however, focus on the impossibility (...) of reproducing the macroscopic measurement results). Although I believe this form of the argument is new, I argue it is essentially a variant of Einstein’s reasoning in the context of the EPR paradox—which is thereby illuminated from a new angle. (shrink)

Using three intuitive notions about causes, including Redhead's robustness condition, I formulate necessary conditions on partial causes. I then demonstrate that we cannot explain the EPR correlations in terms of partial causes unless we abandon the quantum mechanical framework and adopt a nonlocal hidden-variable theory. The argument, unlike its predecessors, does not appeal to relativity theory.

We examine possible causal structures of experiments with entangled quantum objects. Previously, these structures have been obscured by assuming a misleading probabilistic analysis of quantum non locality as 'Outcome Dependence or Parameter Dependence' and by directly associating these correlations with influences. Here we try to overcome these shortcomings: we proceed from a recent stronger Bell argument, which provides an appropriate probabilistic description, and apply the rigorous methods of causal graph theory. Against the standard view that there is only an influence (...) between the measurement outcomes, we show that there must be an influence from one setting to its distant outcome: EPR correlations can only come about if one of the outcomes is a common effect of both settings. Our discussion makes explicit under which assumptions similar conclusions from information theoretic considerations can be interpreted causally. (shrink)