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.
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.
John Stewart Bell’s famous theorem is widely regarded as one of the most important developments in the foundations of physics. Yet even as we approach the 50th anniversary of Bell’s discovery, its meaning and implications remain controversial. Many workers assert that Bell’s theorem refutes the possibility suggested by Einstein, Podolsky, and Rosen (EPR) of supplementing ordinary quantum theory with “hidden” variables that might restore determinism and/or some notion of an observer-independent reality. But Bell himself interpreted the theorem very differently—as establishing an “essential conflict” between the well-tested empirical predictions of quantum theory and relativistic local causality. Our goal is to make Bell’s own views more widely known and to explain Bell’s little-known formulation of the concept of relativistic local causality on which his theorem rests. We also show precisely how Bell’s formulation of local causality can be used to derive an empirically testable Bell-type inequality and to recapitulate the EPR argument.
In this paper, I want to present a family of results that may seem to add up to a new proof of the impossibility of hidden variables. In fact, I very much doubt that that’s really what really emerges, but I think the results are nonetheless interesting because they help to sharpen the discussion of Jon Jarrett’s very useful decompostion theorem, in particular, of the condition he calls locality. Jarrett (1984) and Ballentine and Jarrett (1987) have suggested that the so-called condition of locality is the one that provides the conceptual link between hidden variable theories and relativity: if locality is violated, so is relativity. On the other hand, a theory may violate the condition Jarrett calls completeness without running afoul of relativity. Now I agree with Jarrett and Ballentine about completeness, but I strongly suspect that we have quite a way to go before we really understand what would be involved in a violation of locality.
Many of the heated arguments about the meaning of 'Bellʼs theorem' arise because this phrase can refer to two different theorems that John Bell proved, the first in 1964 and the second in 1976.His 1964 theorem is the incompatibility of quantum phenomena with the dual assumptions of locality and determinism.His 1976 theorem is the incompatibility of quantum phenomena with the unitary property of local causality.This is contrary to Bellʼs own later assertions, that his 1964 theorem began with that single, and indivisible, assumption of local causality (even if not by that name).While there are other forms of Bellʼs theorems-which I present to explain the relation between Jarrett-completeness, 'fragile locality', and EPR-completeness-I maintain that Bellʼs two versions are the essential ones.Although the two Bellʼs theorems are logically equivalent, their assumptions are not, and the different versions of the theorem suggest quite different conclusions, which are embraced by different communities.For realists, the notion of local causality, ruled out by Bellʼs 1976 theorem, is motivated implicitly by Reichenbachʼs principle of common cause and explicitly by the principle of relativistic causality, and it is the latter which must be forgone.Operationalists pay no heed to Reichenbachʼs principle, but wish to keep the principle of relativistic causality, which, bolstered by an implicit 'principle of agent-causation', implies their notion of locality.Thus for operationalists, Bellʼs theorem is the 1964 one, and implies that it is determinism that must be forgone.I discuss why the two 'camps' are drawn to these different conclusions, and what can be done to increase mutual understanding.
Adjusting EPR (to accord with Bohr's insight), and accepting Bell's principles (but not his false inferences), we:— (i) complete the QM account of EPR correlations in a classical way; (ii) deliver Bell's hope for a simple constructive model of EPRB; (iii) justify EPR's belief that additional variables would bring locality and causality to QM's completion; (iv) refute key claims that such variables are impossible — including CHSH, Mermin's three-particle always-vs-never variant of GHZ, and this: in the context of Bell's theorem ‘it's a proven scientific fact that a violation of local realism has been demonstrated theoretically and experimentally,' (Annals of Physics Editors, 2016). In short: we refute Bell's theorem and endorse Einstein's locally-causal Lorentz-invariant worldview.
In papers published in the 25 years following his famous 1964 proof, John Bell refined and reformulated his views on locality and causality. Although his formulations of local causality were in terms of probability, he had little to say about that notion. But assumptions about probability are implicit in his arguments and conclusions. Probability does not conform to these assumptions when quantum mechanics is applied to account for the particular correlations Bell argues are locally inexplicable. This account involves no superluminal action and there is even a sense in which it is local, but it is in tension with the requirement that the direct causes and effects of events be nearby. Introduction I never met John Bell, but his writings have supplied me with a continual source of new insights as I read and reread them over 40 years. As I worked toward a rather different understanding of quantum mechanics he was foremost in my mind as a severe but honest critic of such attempts. We all would love to know what Einstein would have made of Bell's theorem. I confess that the deep regret I feel that Bell cannot respond to this paper is sometimes assuaged by a sense of relief. Locality and Local Causality In his seminal 1964 paper [1], John Bell expressed locality as the requirement that the result of a measurement on one system be unaffected by operations on a distant system with which it has interacted in the past. [2, p. 14] This seems to require that the result of a measurement would have been the same, no matter what operations had been performed on such a distant system. But suppose the result of a measurement were the outcome of an indeterministic process. Then the result of the measurement might have been different even if exactly the same operations (if any) had been performed on that distant system. So can no indeterministic theory satisfy the locality requirement? Bell felt no need to address that awkward question in his 1964 paper [1], since he took the EPR argument to establish that any additional variables needed to restore locality and causalitywould have to determine a unique result of ameasurement.
This open letter challenges Annals of Physics' Editors and Bell's supporters on this front: in the context of Bell's theorem -- after AoP (2016:67) -- ‘it's a proven scientific fact that a violation of local realism has been demonstrated theoretically and experimentally.' We show that such claims under the Bellian canon are curtailed by its foundation on a naive realism that is known to be false; ie, under Bohr's old insight (in our terms), a test may disturb the tested system. Further: (i) We define a general all-embracing local realism -- CLR, commonsense local realism -- the union of local-causality (no causal influence propagates superluminally) and physical-realism (some physical properties change interactively). (ii) Under CLR, with EPR-based variables (and without QM), a thought-experiment delivers a local-realistic account of EPRB and GHZ in 3-space. (iii) Under EPR, mixing common-sense with undergrad math/physics in the classical way so favored by Einstein, we interpret QM locally and realistically. (iv) We find the flaw in Bell's theorem: Bell's 1964:(14a) ≠ Bell's 1964:(14b) under EPRB. (v) EPR (1935) famously argue that additional variables will bring locality and causality to QM's completion; we show that they are right. (vi) Even more famously, Bell (1964) cried ‘impossible' against such variables; we give the shortest possible refutation of his claim. (vii) Using Bell's (1988:88) moot gloss on a fragment of von Neumann's work, we conclude: ‘There's nothing to Bell's theorem -- nor Bellian variants like CHSH (1969), Mermin (1990), Peres (1995); nor Bellian endorsements like those by Bricmont, du Sautoy, Goldstein et al., Maudlin, Norsen, Shimony -- it's not just flawed, it's silly; its assumptions nonsense; it's not merely false but foolish' and misleading. (viii) Our results accord with common-sense, QM, Einstein's principles, EPR's belief and Bell's hopes and expectations.