Arguments by Sorkin (Impossible measurements on quantum fields. In: Directions in general relativity: proceedings of the 1993 International Symposium, Maryland, vol 2, pp 293–305, 1993) and Borsten et al. (Phys Rev D 104(2), 2021. https://doi.org/10.1103/PhysRevD.104.025012 ) establish that a natural extension of quantum measurement theory from non-relativistic quantum mechanics to relativistic quantum theory leads to the unacceptable consequence that expectation values in one region depend on which unitary operation is performed in a spacelike separated region. Sorkin [ 1 ] labels (...) such scenarios ‘impossible measurements’. We explicitly present these arguments as a no-go result with the logical form of a reductio argument and investigate the consequences for measurement in quantum field theory (QFT). Sorkin-type impossible measurement scenarios clearly illustrate the moral that Microcausality is not by itself sufficient to rule out superluminal signalling in relativistic quantum theories that use Lüders’ rule. We review three different approaches to formulating an account of measurement for QFT and analyze their responses to the ‘impossible measurements’ problem. Two of the approaches are: a measurement theory based on detector models proposed in Polo-Gómez et al. (Phys Rev D, 2022. https://doi.org/10.1103/physrevd.105.065003 ) and a measurement framework for algebraic QFT proposed in Fewster and Verch (Commun Math Phys 378(2):851–889, 2020). Of particular interest for foundations of QFT is that they share common features that may hold general morals about how to represent measurement in QFT. These morals are about the role that dynamics plays in eliminating ‘impossible measurements’, the abandonment of the operational interpretation of local algebras \({\mathcal {A}}(O)\) as representing possible operations carried out in region _O_, and the interpretation of state update rules. Finally, we examine the form that the ‘impossible measurements’ problem takes in histories-based approaches and we discuss the remaining challenges. (shrink)

The problem of the status of metaphysics -- what it is and what it is for, what use it is - has been with us for millennia, at least since Plato took issue with the Sophists, and continues to the present day. Here I attempt an intervention in this perennial dispute, with the aim of providing some kind of rapprochement between the factions. This intervention is based on how Charles Sanders Peirce (1839-1914) understood metaphysics and the position presented here is (...) thus called `Peircean realism'. The basic idea is that everyone has a metaphysics and has to have one, just to get by in everyday life, and this is no different for scientific inquirers in their professional work. The subject matter of metaphysics is thus presuppositions, whether it is what we rely on to go shopping or to discover the Higgs boson. We rely on these in our activities and expect them to have an effect on outcomes, so when our expectations are frustrated, doubt may be thrown on our presuppositions. We would thus like the ability to inquire into our presuppositions so as not to repeat mistakes, but our instinctive, evolved capacity for reasoning may not be up the job, since it is entwined with what we take for granted. Instead, Peirce develops a science of good reasoning that includes a theory of inquiry, which would allow us to scrutinise our presuppositions, to perform metaphysical inquiry. The starting point for this science of good reasoning is basic principles of combination and organisation, because these are involved in all activity, and these are Peirce's categories of Firstness, Secondness and Thirdness. This is also where I start in the exposition of and argument for Peircean realism as a scientific -- that is, truth-directed -- metaphysics that provides the best possible general presuppositions to the natural and human sciences, the special sciences that deal with matters in their particularity; that Peircean realism is a viable metaphysics for those sciences. This exposition and argument comprises the first part of this thesis. In the second part, the case for Peircean realism is further bolstered by turning a critical eye on positions that are deficient from the Peircean point of view, in that they lack one or other category and thus starve the special sciences of the resources they need, or that they try to ignore metaphysics entirely. All this is meant to demonstrate that metaphysics is unavoidable, that we need all three of Peirce's categories for a viable metaphysics for the special sciences, and that Peircean realism is just such a metaphysics. (shrink)

Como introducción al monográfico sobre reduccionismo y emergencia brindamos aquí un contexto teórico al debate contemporáneo. Hablaremos primero del acercamiento naturalista en filosofía (§2), así como de dos de las características más importantes de la emergencia: autonomía y universalidad (§3). Finalmente, basándonos en la literatura contemporánea (principalmente en Patricia Palacios y Jessica Wilson, además de Mario Bunge y Alicia Juarrero) presentamos algunas de las definiciones y distinciones más importantes para entender mejor el debate sobre la emergencia (§4).

In recent work, Adlam (2022b), Chen & Goldstein (2022), and Meacham (2023) have defended accounts of laws that take laws to be primitive global constraints. A major advantage of these accounts is that they’re able to accommodate the many different kinds of laws that appear in physical theories. In this paper I’ll present these three accounts, highlight their distinguishing features, and note some key differences that might lead one to favor one of these accounts over the others. I’ll conclude by (...) briefly discussing a version of a “constraint” account that I think is especially attractive. (shrink)

Several philosophers have argued that ‘constraints’ constrain (and thereby explain) by virtue of being modally stronger than ordinary laws of nature. In this way, a constraint applies to all possible systems, for a variety of possibility that is broader (that is, more inclusive) than the variety we employ when we say that the ordinary laws of nature apply to all physically possible systems. Explanations by constraint are thus more broadly unifying than ordinary causal explanations. Philosophical examples of good candidates for (...) constraints have heretofore been drawn almost exclusively from fundamental physics. This paper argues for the existence of such constraints (even multiple levels of them) in at least one human science (linguistics), not just in physics. (shrink)

One of the most intuitive views about the metaphysics of laws of nature is Tim Maudlin's idea of a Fundamental Law of Temporal Evolution. So-called FLOTEs are primitive elements of the universe that produce later states from earlier states. While FLOTEs are at home in traditional Newtonian and non-relativistic quantum mechanical theories (not to mention our pre-theoretic conception of the world), I consider here whether they can be made to work with relativity. In particular, shifting to relativistic spacetimes poses two (...) threats to FLOTEs. First, the lack of a privileged spacelike hypersurface in relativistic spacetime makes it unclear how to understand what produces what. A survey of several conceptions of the nomic production relation compatible with relativity reveals all of them to be lacking. Second, relativity motivates a four-dimensional block universe conception of time, according to which all events that will ever occur already exist. On such a view, it's unclear what work there is to be done by FLOTEs. I consider how a proponent of FLOTEs might respond, but conclude that these combined threats seriously undermine the prospects of a productive conception of laws. In short, if spacetime is relativistic, laws are not productive. (shrink)

Wallace has recently argued that a number of popular approaches to the measurement problem can’t be fully extended to relativistic quantum mechanics and quantum field theory; Wallace thus contends that as things currently stand, only the unitary-only approaches to the measurement problem are viable. However, the unitary-only approaches face serious epistemic problems which may threaten their viability as solutions, and thus we consider that it remains an urgent outstanding problem to find a viable solution to the measurement problem which can (...) be extended to relativistic quantum mechanics. In this article we seek to understand in general terms what such a thing might look like. We argue that in order to avoid serious epistemic problems, the solution must be a single-world realist approach, and we further argue that any single-world realist approach which is able to reproduce the predictions of relativistic quantum mechanics will most likely have the property that our observable reality does not supervene on dynamical, precisely-defined microscopic beables. Thus we suggest three possible routes for further exploration: observable reality could be approximate and emergent, as in relational quantum mechanics with the addition of cross-perspective links, or observable reality could supervene on beables which are not microscopically defined, as in the consistent histories approach, or observable reality could supervene on beables which are not dynamical, as in Kent’s solution to the Lorentzian classical reality problem. We conclude that once all of these issues are taken into account, the options for a viable solution to the measurement problem are significantly narrowed down. (shrink)

The path integral is not typically utilized for analyzing entanglement experiments, in part because there is no standard toolbox for converting an arbitrary experiment into a form allowing a simple sum-over-history calculation. After completing the last portion of this toolbox (a technique for implementing multi-particle measurements in an entangled basis), some interesting 4- and 6-particle experiments are analyzed with this alternate technique. While the joint probabilities of measurement outcomes are always equivalent to conventional quantum mechanics, differences in the calculations motivate (...) a number of foundational insights, concerning nonlocality, retrocausality, and the objectivity of entanglement itself. (shrink)

Mental causation, idea that it is us – via our minds – who cause bodily actions is as commonsensical as it is indispensable for our understanding of ourselves as rational agents. Somewhat less uncontroversial, but nonetheless widespread (at least among ordinary people) is the idea that the mind is non-physical, following the intuition that what is physical can neither act nor think nor judge morally. Taken together, and cast into a metaphysical thesis, the two intuitions yield interactive dualism: the view (...) that human persons and their minds are non-physical but can nonetheless interact with their bodies, most notably through their brains. This thesis has two main objectives: first, to defend interactive dualism against objections, and second, to show how it can blend in with a physical world in which laws of nature hold. The first part (chapter 1) consists in a brief motivation of interactive dualism as opposed to non-interactive dualism. I argue that non-interactive, epiphenomenalist dualism sacrifices so many crucial aspects of our human existence that interactive dualism is highly to be preferred to it, barring even stronger counterarguments against the latter. It is those putative counterarguments I address in parts II and III. Part II takes on the philosophical objections from the causal closure of the physical and from causal heterogeneity. The former takes the success of physics and physiology as basis for the doctrine of the causal closure of the physical (CCP). I argue against this that there is not only no convincing argument for CCP, but also that any science-based belief in CCP cannot be epistemically justified. As regards the causal heterogeneity objection, it is ‘weighed and found wanting’, because it relies on unwarranted assumptions about causation. In part III, I examine the objection from energy conservation. It roughly says that if interactive dualism were true, then energy would not be conserved, which physics taught us cannot be the case. My reply is that the underlying conception of energy (and momentum) conservation is wrong-headed and not the one that actual physicists use. Instead of being categorical and global, conservation laws are conditional and local, thereby making natural room for mental interaction. Some dualists, however, have sought to make interactive dualism conservation-friendly, notably by invoking quantum physics; I show that these attempts are unnecessary and create more problems than they solve. Finally, in chapter 9, I turn the tables on non-interactionists by investigating current neurophysiological literature on volitional actions, which, though not addressing the question directly, still encourages the interactive dualist picture more than a non-interactionist one. Part IV is about the interplay between interactive dualism and the laws of nature. The ultimate goal is, if possible, to come up with a theory of the laws of nature that explains the lawlike behavior of nature and at the same time makes room for interaction. I begin by pointing out that the laws of nature are or at least should be what physicalists worry about (chapter 10). I then proceed with a historical survey on the development of the notion of laws of nature (chapter 11) that sheds light on its theistic origin. This is followed by an inquiry into the question how a law of nature could possibly be broken (chapter 12) and a survey of the extant metaphysical theories of the laws of nature with special regard to their receptivity to interaction (chapter 13). Finally, in chapter 14 I develop a theory of the laws of nature both faithful to their divine origin and the possibility of mental interaction: dispositionalist divine decretalism, a synthesis of dispositionalism and Jeffrey Koperski’s divine decretalism. (shrink)

Physicists are increasingly beginning to take seriously the possibility of laws outside the traditional time-evolution paradigm; yet many popular definitions of determinism are still predicated on a time-evolution picture, making them manifestly unsuited to the diverse range of research programmes in modern physics. In this article, we use a constraint-based framework to set out a generalization of determinism which does not presuppose temporal evolution, distinguishing between strong, weak and delocalised holistic determinism. We discuss some interesting consequences of these generalized notions (...) of determinism, and we show that this approach sheds new light on the long-standing debate surrounding the nature of objective chance. (shrink)

In recent years the quantum foundations community has seen increasing interest in the possibility of using retrocausality as a route to rejecting the conclusions of Bell’s theorem and restoring locality to quantum physics. On the other hand, it has also been argued that accepting nonlocality leads to a form of retrocausality. In this article we seek to elucidate the relationship between retrocausality and locality. We begin by providing a brief schema of the various ways in which violations of Bell’s inequalities (...) might lead us to consider some form of retrocausality. We then consider some possible motivations for using retrocausality to rescue locality, arguing that none of these motivations is sufficient to show that local retrocausal theories should always be preferred to nonlocal retrocausal theories, and therefore there is no clear reason to focus research efforts entirely on seeking local retrocausal models. Next, we examine several different conceptions of retrocausality, concluding that ‘all-at-once’ retrocausality is more coherent than the alternative dynamical picture. We then argue that since the ‘all-at-once’ approach requires probabilities to be assigned to entire histories, locality is not playing any crucial role within this picture. Thus we conclude that using retrocausality as a way to rescue locality may not be the right route to retrocausality. Finally, we demonstrate that accepting the existence of nonlocality and insisting on the nonexistence of preferred reference frames leads naturally to the acceptance of a form of retrocausality, albeit one which is not mediated by physical systems travelling backwards in time. We argue that this is the more natural way to motivate retrocausal models of quantum mechanics. (shrink)

The Great Divide in metaphysical debates about laws of nature is between Humeans, who think that laws merely describe the distribution of matter, and non-Humeans, who think that laws govern it. The metaphysics can place demands on the proper formulations of physical theories. It is sometimes assumed that the governing view requires a fundamental / intrinsic direction of time: to govern, laws must be dynamical, producing later states of the world from earlier ones, in accord with the fundamental direction of (...) time in the universe. In this paper, we propose a minimal primitivism about laws of nature (MinP) according to which there is no such requirement. On our view, laws govern by constraining the physical possibilities. Our view captures the essence of the governing view without taking on extraneous commitments about the direction of time or dynamic production. Moreover, as a version of primitivism, our view requires no reduction / analysis of laws in terms of universals, powers, or dispositions. Our view accommodates several potential candidates for fundamental laws, including the principle of least action, the Past Hypothesis, the Einstein equation of general relativity, and even controversial examples found in the Wheeler-Feynman theory of electrodynamics and retrocausal theories of quantum mechanics. By understanding governing as constraining, non-Humeans who accept MinP have the same freedom to contemplate a wide variety of candidate fundamental laws as Humeans do. (shrink)

There are two metaphysical pictures of spacetime: The evolutionary picture and the all-at-once picture. According to the evolutionary picture, spacetime is nothing but the evolution of space over time. In contrast, the all-at-once picture considers spacetime as ‘a global, four-dimensional boundary value problem’ that can be solved only in an all-at-once manner, i.e. as a whole which is fundamentally four-dimensional and non-decomposable into spatial and temporal parts. The two most-known formulations of general theory of relativity, i.e. the Hamiltonian (or the (...) canonical) and the Lagrangian (or the standard) formulations, enjoy the evolutionary and all-at-once pictures of spacetime respectively. Here, we have argued that (1) the all-at-once picture is more aligned with the philosophy of relativity theory, i.e. uniting space and time into spacetime, (2) the evolutionary picture is not as general as the all-at-once, since only in special cases, such as globally hyperbolic spacetimes, is it possible to deal with spacetime as the evolution of a spatial slice over time, and (3) the all-at-once picture paves the way to better understanding _four-dimensional_ physical entities, like event horizons, which cannot be explained within an evolutionary picture without raising a paradox. Therefore, the evolutionary picture is neither the _fundamentally-true_ nor the _naturally-chosen_ picture of spacetime. Rather, we choose the evolutionary picture for practical and computational reasons. While the all-at-once picture seems a more appropriate description of the quantum and cosmological reality, the evolutionary picture can be applied occasionally and locally, or quasi-locally, and is not the proper metaphysical picture of spacetime at the fundamental level of reality. (shrink)

In this paper, it is argued that, contrary to some suggestions in the philosophical literature, dispositions cannot replace laws in the description of the physical world. If for a certain type of physical situation a well-working law-based account is available, then it is not possible to describe that situation equally well in terms of dispositions. Using an example consisting of four laws (Coulomb’s law, Newton’s law of gravitation, the rule for the composition of forces and Newton’s second law), it is (...) shown that when one attempts to replace a law-based account with a disposition-based account, the latter turns out to be either less informative or inferior with respect to theoretical virtues, such as simplicity, unification, non-triviality of predictions and explanatory power. Laws are also better suited to deal with interactions and their screening off. Using inference to the best explanation, one can conclude from this comparison that it is laws rather than dispositions that should be included in our ontological picture of nature. (shrink)