Necessity, but not possibility, is typically thought to be rare and suspicion-worthy. This manifests in an asymmetry in the burden of proof incurred by modal claims. In general, claims to the effect that some proposition is impossible/necessary require significant argumentative support and, in general, claims to the effect that some proposition is possible/contingent are thought to be justified freely or by default. Call this the possibility bias. In this paper, I argue that the possibility bias is not epistemically justified. We (...) should regard possibility with at least as much suspicion, that is to say as incurring at least as much of an explanatory demand, as necessity. In fact, I suggest that we might even be justified in reversing the burden of proof asymmetry and adopting a necessity bias. This has quite radical implications for philosophical methodology and hence for many first-order philosophical concerns. (shrink)

In The Context of Laws of Nature Structural Humeanism vs. Classical Humeanism -/- In the context of the laws of nature, philosophers of science have developed some views in order to adopt an attitude towards recurring events in nature. In this respect, it has been discussed whether there is any driving force underlying the regular behaviours and movements we encounter in nature, and two approaches have emerged as a result of the discussion: A view that there are certain driving forces (...) or causal relations in the ground, and an opposing view that claims that there are no causal relations in the ground, but there are regularities in nature. Views such as the latter are generally described as the Humean view. Such views are also called regularity theories. Throughout this article, the statements referred to as regularity are characterised as the Humean view. Since the article will be centred on the Humean view, views such as the first view, such as dispositional essentialism or structural realism, are not the concern of this article. The article favours the Structural Humean approach over the classical Humean approach. The classical Humean approach is centred on the views of David Lewis and is concerned with distinguishing between laws of nature seen as accidental generalisations and regularities. While it tries to make such a distinction by constructing nature through a mosaic, the Structural Humean approach is an approach that develops Lewis’s claims and tries to shape nature with the concept of structure rather than mosaic. Thus, it is seen as an approach that provides more information than the Classical Humean approach in terms of creating a philosophical infrastructure for explaining nature in terms of modern physics. Through Psillos, Structural Humeanism tried to place the concept of natural pattern into the structure in order to gain metaphysical solidity and tried to bring the Structural Humean approach closer to the Structural Realism camp. Thus, the classically epistemologically important Humean approach has made a significant progress in positioning it on the realist wing. As a result of all these studies, the Structural Humean approach has been defended as a philosophical approach that offers useful arguments for modern physics compared to the Classical Humean approach. -/- Keywords: Humeanism, Regularity, Laws of Nature, Best System Account, Structural Humeanism, Natural Patterns. (shrink)

The question of whether Everettian quantum mechanics (EQM) justifies the existence of metaphysical indeterminacy has recently come to the fore. Metaphysical indeterminacy has been argued to emerge from three sources: coherent superpositions, the indefinite number of branches in the quantum multiverse and the nature of these branches. This paper reviews the evidence and concludes that those arguments don’t rely on EQM alone and rest on metaphysical auxiliary assumptions that transcend the physics of EQM. We show how EQM can be ontologically (...) interpreted without positing metaphysical indeterminacy by adopting a deflationary attitude towards branches. Two ways of developing the deflationary view are then proposed: one where branches are eliminated, and another where they are reduced to the universal quantum state. (shrink)

One might suppose that Everettian quantum mechanics (EQM) is inhospitable to metaphysial indeterminacy (MI), given that, as A. Wilson (2020) puts it, "the central idea of EQM is to replace indeterminacy with multiplicity" (77). But as Wilson goes on to suggest, the popular decoherence-based understanding of EQM (henceforth: DEQM) appears to admit of indeterminacy in both world number and world nature, where the latter indeterminacy---our focus here---is plausibly metaphysical. After a brief presentation of DEQM (S1), we bolster the case for (...) there being MI in world nature in DEQM (S2). The remainder of the paper is devoted to a comparative assessment of the two main approaches to MI for purposes of accommodating this MI---namely, a metaphysical supervaluationist approach (as per Barnes and Williams 2011) and a determinable-based approach (as per Wilson 2013 and Calosi and Wilson 2018 and 2021). We briefly describe each approach (S3), then offer arguments in favour of a determinable-based approach to world nature MI in DEQM (S4). (shrink)

Here is a puzzling phenomenon. Moral theories are typically thought to be necessary. If act utilitarianism is true, for example, then it is necessarily true. However, scientific theories are typically thought to be contingent. If quantum field theory is true, it’s not necessarily true — the world could have been Newtonian. My aim is to explore this discrepancy between domains. -/- In particular, I explore the role of what I call `internality’ intuitions in motivating necessitism about both moral and scientific (...) domains. In effect, these internality intuitions tell against the explanatory role of certain `external’ entities – like moral or scientific principles. I’ll suggest that perhaps these internality intuitions are more compelling in the moral case than the scientific case. If so, this would rationalize the combination of moral necessitism and scientific contingentism. (shrink)

At the core of the recent debate over moral debunking arguments is a disagreement between explanationist and modalist approaches. Explanationists think that the lack of an explanatory connection between our moral beliefs and the moral truths, given a non-naturalist realist conception of morality, is a reason to reject non-naturalism. Modalists disagree. They say that, given non-naturalism, our beliefs have the appropriate modal features with respect to truth -- in particular they are safe and sensitive -- so there is no problem. (...) -/- There is something of a stand-off here. I argue, though, that by looking at the role explanatory and modal factors have to play in theory choice more generally, and, in particular, by considering the practice of theory choice in science, we can see that the explanationist is right. The lack of an explanatory connection between our moral beliefs and the moral truths is a reason to reject non-naturalist realism about morality. (shrink)

Modal dispositionalists hold that dispositions provide the foundation of metaphysical necessity and possibility. According to the kind of modal dispositionalism that can be found in the present literature, a proposition p is possible just in case some things are disposed to be such that p. In the first part of this paper I show that combining this classic form of dispositionalism with the assumptions that the laws of nature are necessary and deterministic and that all dispositions are forward-looking in time (...) leads to the unattractive conclusion that every truth is necessary. I argue that the classic dispositionalist should be troubled by this result and in the second part of the paper I suggest a novel variant of dispositionalism that avoids it. This extended form of dispositionalism allows that some propositions are only indirectly underwritten by dispositions. (shrink)

'Chains of Being' argues that there can be infinite chains of dependence or grounding. Cameron also defends the view that there can be circular relations of ontological dependence or grounding, and uses these claims to explore issues in logic and ontology.

It is sometimes argued that, given its detachment from our current most successful science, analytic metaphysics has no epistemic value because it contributes nothing to our knowledge of reality. Relatedly, it is also argued that metaphysics properly constrained by science can avoid that problem. In this paper we argue, however, that given the current understanding of the relation between science and metaphysics, metaphysics allegedly constrained by science suffers the same fate as its unconstrained sister; that is, what is currently thought (...) of as scientifically respectful metaphysics may end up also being without epistemic value. The core of our claim is that although much emphasis is put on the supposed difference between unconstrained analytic metaphysics, in opposition to scientifically constrained metaphysics, it is largely forgotten that no clear constraining relation of metaphysics by science is yet available. (shrink)

My topic in this paper is the relationships of metaphysical priority which might hold between the different alethic modal statuses—necessity, contingency, possibility and impossibility. In particular, I am interested in exploring the view that the necessity of necessities is ungrounded while the contingency of contingencies is grounded—a scenario I call ‘necessity first’. I will explicate and scrutinize the contrast between necessity first and its ‘contingency first’ contrary, and then compare both views with ‘multimodal’ and ‘amodal’ alternatives, drawing on David Lewis’s (...) modal realism and Barbara Vetter’s potentialism as example cases. I will then defend the necessity-first point of view from a reversed version of Blackburn’s classic dilemma against theories of the source of necessity. (shrink)

Carnap's conception of linguistic frameworks is widespread; however, it is not entirely clear nor consensual to pinpoint what is the influence of his stance within the traditional realist/anti-realist debate. In this paper, we place Carnap as a proponent of a scientific realist stance, by presenting what he called “linguistic realism”. Some possible criticisms are considered, and a case study is offered with wave function realism, a popular position in the philosophy of quantum mechanics.

In contemporary metaphysics, the doctrine that the fundamental facts are those which are wholly ungrounded is the received view or something near enough. Against this radical brutalism, several metaphysicians argued in favour of the existence of fundamental facts that are moderately brute or merely partially grounded. However, the arguments for moderately brute facts rely on controversial metaphysical scenarios. This paper aims to counteract the tendency in favour of radical brutalism on scientific grounds. It does so by showing that naturalistic metaphysicians (...) can appeal to plausible considerations from physical theory to establish the existence of moderately brute facts. But should the naturalistic metaphysician embrace moderate brutalism, namely the view that the fundamental facts are those which are merely partially ungrounded? Here I argue for a negative answer, recommending a more inclusive pluralism about the kinds of brute facts we can expect to find in nature. (shrink)

Priority monism is the doctrine that there is only one basic object: the entire cosmos. Priority monists often take this to be a metaphysically necessary thesis. I explore the consequences of modalizing the priority monist thesis. I argue that, modulo some assumptions, the modalized thesis entails the necessary existence of the actual cosmos. I further argue that, if the modalized thesis is true, and the actual cosmos necessarily exists, then the only possible concrete objects are the actually existing ones.

Distinctions in fundamentality between different levels of description are central to the viability of contemporary decoherence-based Everettian quantum mechanics (EQM). This approach to quantum theory characteristically combines a determinate fundamental reality (one universal wave function) with an indeterminate emergent reality (multiple decoherent worlds). In this chapter I explore how the Everettian appeal to fundamentality and emergence can be understood within existing metaphysical frameworks, identify grounding and concept fundamentality as promising theoretical tools, and use them to characterize a system of explanatory (...) levels (with associated laws of nature) for EQM. This Everettian level structure encompasses and extends the ‘classical’ levels structure. The ‘classical’ levels of physics, chemistry, biology, etc. are recovered, but they are emergent in character and potentially variable across Everett worlds. EQM invokes an additional fundamental level, not present in the classical levels picture, and a novel potential role for self-location in interlevel metaphysics. When given a modal realist interpretation, EQM also makes trouble for supervenience-based approaches to levels. (shrink)

In On the Plurality of Worlds (Lewis 1986), David Lewis imposes a condition on realist theories of modality which he calls ‘plenitude’. Lewis apparently assigns this condition considerable importance, and uses it to motivate his Humean principle of recombination, but he never says exactly what plenitude amounts to. This chapter first sets aside some obvious ways of reconstructing the plenitude criterion which do not fit with the textual evidence. An objection to modal realism due to John Divers and Joseph Melia (...) (Divers and Melia 2002) is diagnosed as equivocating between an overly-demanding plenitude constraint and a weaker constraint which fails to establish their conclusion. An alternative deflationary interpretation of the plenitude condition has it following from an application of standard theoretical virtues to a modal realist’s total theory; Lewis’ correspondence provides new evidence in support of this interpretation. The deflationary plenitude criterion also has broader application, beyond Lewisian modal realism. (shrink)

Quantum gravity’s suggestion that spacetime may be emergent and so only exist contingently would force a radical reconception of extant analyses of laws of nature. Humeanism presupposes a spatiotemporal mosaic of particular matters of fact on which laws supervene; primitivism and dispositionalism conceive of the action of primitive laws or of dispositions as a process of ‘nomic production’ unfolding over time. We show how the Humean supervenience basis of non-modal facts and primitivist or dispositionalist accounts of nomic production can be (...) reconceived, avoiding a reliance on fundamental spacetime. However, it is unclear that naturalistic forms of Humeanism can maintain their commitment to there being no necessary connections among distinct entities. Furthermore, non-temporal conceptions of production render this central concept more elusive than before. In fact, the challenges run so deep that the survival of the investigated analyses into the era of quantum gravity is questionable. (shrink)

In this review, I specify the metametaphysical background against which Alastair Wilson’s “_The Nature of Contingency_” (Oxford University Press, 2020) should be properly understood. Metaphysics, as a philosophical discipline, is standing on thin ice. The caricature of the situation is polarized, and is often presented as follows: metaphysics is either entirely extracted from science or it is entirely independent of science. There is a recent trend that focuses on the middle ground between these extremes, searching the philosophical literature for metaphysical (...) theories that can fill the gap, i.e., leaving metaphysics as a free discipline to produce spoils for the eventual needs of philosophers of science. We can appreciate it better with the following distinction between the tasks of ontology and metaphysics, as complementary disciplines. If, on the one hand, we understand ontology as dealing with what exists, we can somehow extract the entities that are existentially postulated by scientific theories. Metaphysics, on the other hand, would be located as an extra layer, in charge of investigating questions about the nature of the entities obtained in this “naturalized ontology”. As a tailor, Wilson adjusts a metaphysical theory in order to perfectly dress the physical and ontological nuances of Everettian quantum mechanics, thus creating a metaphysical theory that gives us intelligibility, with the concept of modality, in two areas: in quantum mechanics, and analytic metaphysics. (shrink)

According to the Determinable Based Account of metaphysical indeterminacy, there is MI when there is an indeterminate state of affairs, roughly a state of affairs in which a constituent object x has a determinable property but fails to have a unique determinate of that determinable. There are different ways in which x might have a determinable but no unique determinate: x has no determinate—gappy MI, or x has more than one determinate—glutty MI. Talk of determinables and determinates is usually constructed (...) as relative to levels of determination. In this paper I first provide a formal construction for determinables and determinates that pays crucial attention to intermediate levels of determination, and then explore the consequences for the DBA of introducing such intermediate levels. In particular, I argue that intermediate levels of determination highlight crucial differences between gappy and glutty cases of MI, and allow one to introduce a third way of indeterminacy, glappy MI. (shrink)

⦿ In my dissertation I introduce, motivate and take the first steps in the implementation of, the project of naturalising modal metaphysics: the transformation of the field into a chapter of the philosophy of science rather than speculative, autonomous metaphysics. -/- ⦿ In the introduction, I explain the concept of naturalisation that I apply throughout the dissertation, which I argue to be an improvement on Ladyman and Ross' proposal for naturalised metaphysics. I also object to Williamson's proposal that modal metaphysics (...) --- or some view in the area --- is already a quasi-scientific discipline. -/- ⦿ Recently, some philosophers have argued that the notion of metaphysical modality is as ill defined as to be of little theoretical utility. In the second chapter I intend to contribute to such skepticism. First, I observe that each of the proposed marks of the concept, except for factivity, is highly controversial; thus, its logical structure is deeply obscure. With the failure of the "first principles" approach, I examine the paradigmatic intended applications of the concept, and argue that each makes it a device for a very specific and controversial project: a device, therefore, for which a naturalist will find no use for. I conclude that there is no well-defined or theoretically useful notion of objective necessity other than logical or physical necessity, and I suggest that naturalising modal metaphysics can provide more stable methodological foundations. -/- ⦿ In the third chapter I answer a possible objection against the in-principle viability of the project: that the concept of metaphysical modality cannot be understood through the philosophical analysis of any scientific theory, since metaphysical necessity "transcends'' natural necessity, and science only deals with the latter. I argue that the most important arguments for this transcendence thesis fail or face problems that, as of today, remain unsolved. -/- ⦿ Call the idea that science doesn't need modality, "demodalism''. Demodalism is a first step in a naturalistic argument for modal antirealism. In the fourth chapter I examine six versions of demodalism to explain why a family of formalisms, that I call "spaces of possibility'', are (i) used in a quasi-ubiquitous way in mathematised sciences (I provide examples from theoretical computer science to microeconomics), (ii) scientifically interpreted in modal terms, and (iii) used for at least six important tasks: (1) defining laws and theories; (2) defining important concepts from different sciences (I give several examples); (3) making essential classifications; (4) providing different types of explanations; (5) providing the connection between theory and statistics, and (6) understanding the transition between a theory and its successor (as is the case with quantisation). -/- ⦿ In fifth chapter I propose and defend a naturalised modal ontology. This is a realism about modal structure: my realism about constraints. The modal structure of a system are the relationships between its possible states and between its possible states and those of other systems. It is given by the plurality of restrictions to which said system is subject. A constraint is a factor that explains the impossibility of a class of states; I explain this concept further. First, I defend my point of view by rejecting some of its main rivals: constructive empiricism, Humean conventionalism, and wave function realism, as they fail to make sense of quantum chaos. This is because the field requires the notion of objective modal structure, and the mentioned views have trouble explaining the modal facts of quantum dynamics. Then, I argue that constraint realism supersedes these views in the context of Bohm's standard theory and mechanics, and underpins the study of quantum chaos. Finally, I consider and reject two possible problems for my point of view. -/- ⦿ A central concern of modal metaphysicians has been to understand the logical system that best characterises necessity. In the sixth chapter I intend to recover the logical project applied to my naturalistic modal metaphysics. Scientists and philosophers of science accept different degrees of physical necessity, ranging from purely mathematically necessary facts that restrict physical behaviour, to kinetic principles, to particular dynamical constraints. I argue that this motivates a multimodal approach to modal logic, and that the time dependence of dynamics motivates a logic of historical necessity. I propose multimodal propositional (classical) logics for Bohmian mechanics and the Everettian theory of many divergent worlds, and I close with a criticism of Williamson's approach to the logic of state spaces of dynamic systems. (shrink)

We ponder the question whether quantum physics has had any influence on philosophy, and if not, whether it ought to have had any. Answers to these questions are provided, and they turn out to depend onwhichbranch of the tree of philosophy we sweep, sway and swing, and evenwhichtwig of the branch we touch when we sweep, sway and swing.

In many different ontological debates, anti-arbitrariness considerations push one towards two opposing extremes. For example, in debates about mereology, one may be pushed towards a maximal ontology (mereological universalism) or a minimal ontology (mereological nihilism), because any intermediate view seems objectionably arbitrary. However, it is usually thought that anti-arbitrariness considerations on their own cannot decide between these maximal or minimal views. I will argue that this is a mistake. Anti-arbitrariness arguments may be used to motivate a certain popular thesis in (...) the philosophy of mathematics that rules out the maximalist view in many different ontological debates. (shrink)

As a candidate theory of quantum gravity, the popularity of string theory has waxed and waned over the past four decades. One current source of scepticism is that the theory can be used to derive, depending upon the input geometrical assumptions that one makes, a vast range of different quantum field theories, giving rise to the so-called landscape problem. One apparent way to address the landscape problem is to posit the existence of a multiverse; this, however, has in turn drawn (...) heightened attention to questions regarding the empirical testability and predictivity of string theory. We argue first that the landscape problem relies on dubious assumptions and does not motivate a multiverse hypothesis. Nevertheless, we then show that the multiverse hypothesis is scientifically legitimate and could be coupled to string theory for other empirical reasons. Looking at various cosmological approaches, we offer an empirical criterion to assess the scientific status of multiverse hypotheses. (shrink)

Knowing Our Limits. By Ballantyne Nathan.

Fragmentalism was originally introduced as a new A-theory of time. It was further refined and discussed, and different developments of the original insight have been proposed. In a celebrated paper, Jonathan Simon contends that fragmentalism delivers a new realist account of the quantum state—which he calls conservative realism—according to which: the quantum state is a complete description of a physical system, the quantum state is grounded in its terms, and the superposition terms are themselves grounded in local goings-on about the (...) system in question. We will argue that fragmentalism, at least along the lines proposed by Simon, does not offer a new, satisfactory realistic account of the quantum state. This raises the question about whether there are some other viable forms of quantum fragmentalism. (shrink)

Anscombe's Intention: A Guide. By Schwenkler John.

Proposed derivations of the Born rule for Everettian theory are controversial. I argue that they are unnecessary but may provide justification for a simplified version of the Principal Principle. It’s also unnecessary to replace Everett’s idea that a subject splits in measurement contexts with the idea that subjects have linear histories which partition Many worlds? Everett, quantum theory, and reality, Oxford University Press, Oxford, pp 181–205, 2010; Wallace in The emergent multiverse, Oxford University Press, Oxford, 2012, Chapter 7; Wilson in (...) Br J Philos Sci 64:709–737, 2013; The nature of contingency: quantum physics as modal realism, Oxford University Press, Oxford, forthcoming). Linear histories were introduced to provide a concept of pre-measurement uncertainty and I explain why pre-measurement uncertainty for splitting subjects is after all coherent, though not necessary because Everett’s original fission interpretation of branching can arguably be rendered coherent without it, via reference to Vaidman, Tappenden, Sebens and Carroll and McQueen and Vaidman. A deterministic and probabilistic quantum mechanics can be made intelligible by replacing the standard collapse postulate with a no-collapse postulate which identifies objective probability with relative branch weight, supplemented by the simplified Principal Principle and some revisionary metaphysics. (shrink)

The Many-Worlds Interpretation (MWI) is an approach to quantum mechanics according to which, in addition to the world we are aware of directly, there are many other similar worlds which exist in parallel at the same space and time. The existence of the other worlds makes it possible to remove randomness and action at a distance from quantum theory and thus from all physics.

It is often claimed that the many worlds theory is to be preferred over other realist interpretations of quantum mechanics for its ability to avoid the kind of action at a distance that plagues both hidden variables and collapse models. The aim of this paper is address the question of whether branching should be viewed as a causal process that spreads out from a localized region as some authors (Wallace (2012), Blackshaw, Huggett, and Ladyman (manuscript)) have such suggested, or whether (...) it occurs globally across the total quantum state at an instant as others insist (Sebens and Carroll (2018), McQueen and Vaidman (2019)). An appeal of the local branching model is it that it ensures that branching never involves superluminal influences. After clarifying these two models, the paper will consider the argument in favor of local branching, and then four concerns one might have about that model, that speak in favor of regarding branching as global and instantaneous. Ultimately, although the first three concerns may be addressed by advocates of local branching, the fourth is shown to be more convincing, and speaks in favor of regarding branching as a global, instantaneous change, even if it is a change that is triggered by a local, causal process (decoherence). The last part of paper clarifies the proposed model of branching as global, and explains how it is not in tension with relativity or the many worlds interpretations’ claim to avoid spooky action at a distance. (shrink)

This paper defends an account of the laws of nature in terms of irreducibly modal properties (aka powers) from the threat posed by functional laws, conservation laws and symmetries. It thus shows how powers theorists can avoid ad hoc explanations and resist an inflated ontology of powers and governing laws. The key is to understand laws not as flowing from the essences of powers, as per Bird (2007), but as features of a description of how powers are possibly distributed, as (...) per Demarest (2017), Kimpton-Nye (2017, 2021) and Williams (2019); call this the Powers-BSA. This underappreciated powers-based account of laws is continuous with actual scientific practice and thereby quite naturally accommodates functional laws, conservation laws and symmetries. This paper thus positions the Powers-BSA as the leading anti-Humean account of the relationship between laws and properties. (shrink)

It’s generally taken to be established that no local hidden-variable theory is possible. That conclusion applies if our world is a _thread_, where a thread is a world where particles follow trajectories, as in Pilot-Wave theory. But if our world is taken to be a _set_ of threads locality can be recovered. Our world can be described by a _many-threads_ theory, as defined by Jeffrey Barrett in the opening quote. Particles don’t follow trajectories because a particle in our world is (...) a set of _elemental_ particles following different trajectories, each in a thread. The “elements” of a superposition are construed as subsets in such a way that a particle in our world only has definite position if all its set-theoretic elements are at corresponding positions in each thread. Wavefunction becomes a 3D density distribution of particles’ subset measures, the stuff of an electron’s “probability cloud”. Current Pilot-Wave theory provides a non-relativistic dynamics for the elemental particles (approximated by Many Interacting Worlds theory). EPR-Bell nonlocality doesn’t apply because the relevant measurement outcomes in the absolute elsewhere of an observer are always in superposition. (shrink)

A strongly deterministic theory of physics is one that permits exactly one possible history of the universe. In the words of Penrose (1989), "it is not just a matter of the future being determined by the past; the entire history of the universe is fixed, according to some precise mathematical scheme, for all time.” Such an extraordinary feature may appear unattainable in a world like ours. In this paper, I show that it can be achieved in a simple way and (...) discuss its implications for metaphysics and philosophy of science, including natural properties, free will, explanation, and modality. First, I propose a precise definition of strong determinism. Next, I discuss its philosophical ramifications and a toy example. Finally, I provide a realistic example of a strongly deterministic (and simple) physical theory---the Everettian Wentaculus. A surprising consequence is that whether or not our world is strongly deterministic may be empirically underdetermined. (shrink)

The Nature of Contingency: Quantum Physics as Modal Realism. By Wilson Alastair.

It has been argued that non-relativistic quantum mechanics is the best hunting ground for genuine examples of metaphysical indeterminacy. Approaches to metaphysical indeterminacy can be divided into two families: meta-level and object-level accounts. It has been shown :27–245, 2010. https://doi.org/10.1080/00048400903097786; Skow in Philosophical Quarterly 60:851–858, 2010) that the most popular version of the meta-level accounts, namely the metaphysical supervaluationism proposed by Barnes and Williams, fails to deal with quantum indeterminacy. Such a fact has been taken by many as a challenge (...) to adapt supervaluationism to quantum cases. In this paper, I will focus on the very last of these attempts, i.e. the situation semantics account proposed by Darby and Pickup. After having shown where quantum indeterminacy arises and having surveyed the assumptions endorsed by the participants of the debate, I turn to Darby and Pickup’s proposal. I argue that, despite the machinery introduced, their account still fails to account for quantum indeterminacy. After considering some possible counterarguments, I suggest in the conclusion that one can plausibly extend the argument to those meta-level approaches that treat quantum indeterminacy as worldly indecision. (shrink)

This paper argues for the following disjunction: either we do not live in a world with a branching temporal structure, or backwards time travel is nomologically impossible, given the initial state of the universe, or backwards time travel to our space-time location is impossible given large-scale facts about space and time. A fortiori, if backwards time travel to our location is possible, we do not live in a branching universe.

It is plausible that the models of our scientific theories correspond to possibilities. But exactly which models of which scientific theories stand in this correspondence? The answers to this question hinted at so far in the literature are too restrictive: they don't support the idea that the models of many of our best scientific theories correspond to physical possibilities. The paper thus provides a novel proposal for guiding belief about physical possibilities based on physics. The proposal draws on the notion (...) of an effective theory: a theory that applies very well to a particular, restricted domain. We argue that it is the models of effective theories that we should believe correspond, at least in part, to physical possibilities. It is thus effective theories that should guide modal reasoning in science. (shrink)

This thesis is composed of three essays on the perdurantist approach to persistence and identity over time. In Chapter 1, I discuss how the following papers are to be understood as parts of a unified perdurantist account of persistence over time. This chapter also outlines some of my philosophical assumptions and provides some background information about the metaphysics of persistence. In Chapter 2, I respond to the objection that the worm theory is unable to account for our intuitions about ordinary (...) counting sentences. I do this by invoking the standard linguistic phenomenon of covert quantifier domain restriction and supplementing the worm theory with situation semantics. My version of the worm theory makes our intuitive judgements come out true, and it does so well enough that there is no need to adopt the stage theory or revisionary theories of counting. Furthermore, my version of the worm theory offers a unified account of event- and object-related counting. Chapter 3 focuses on a commonly neglected difference between different kinds of perdurantism, which are differences in mereological priority. I discuss three different views: parts-first perdurantism, no-priority perdurantism, and wholes-first perdurantism. I briefly outline all three views and some of the motivations for each of them. I fend off objections from and motivations for no-priority perdurantism. I also contend that intraperdurantist debates about phenomenology ought not to be framed with respect to these forms of perdurantism. Instead, I suggest that the relativity of simultaneity presents an interesting scenario for parts-first and wholes-first perdurantists. I respond to Thomas Pashby’s arguments against the doctrine of temporal parts in Chapter 3. Pashby argues that metaphysicians ought to give an account of how quantum systems persist over time and that nonrelativistic quantum mechanics is incompatible with perdurantism. I contend that his arguments rely on controversial, non-standard assumptions about the existence and importance of time observables. I demonstrate that perdurantists have no problem giving an account of how quantum systems persist over time in reference to an external time parameter. Finally, I conclude with a summary of my arguments and some thoughts about directions for future research. (shrink)

The Everett interpretation of quantum mechanics divides naturally into two parts: first, the interpretation of the structure of the quantum state, in terms of branching, and second, the interpretation of this branching structure in terms of probability. This is the second of two reviews of the Everett interpretation, and focuses on probability. Branching processes are identified as chance processes, and the squares of branch amplitudes are chances. Since branching is emergent, physical probability is emergent as well.

Eternalism is a metaphysical view regarding the nature of time. It posits the equal existence of all times: the past, the present, and the future. Every event, from the big bang to the heat death of the universe, including our births and deaths, is equally real. -/- Under standard eternalism, temporal locations are somewhat akin to spatial locations. No place is exclusively real. When someone says that they stand ‘here’, it is clear that the term ‘here’ refers to their position. (...) ‘Back’ and ‘front’ exist as well. Eternalists stress that ‘now’ is indexical in a similar way. It is equally real with ‘past’ and ‘future’. Events are classified as past, present, or future from some perspective. -/- Eternalism is contrasted with presentism, which maintains that only present things exist and with the growing block view (also known as possibilism or no-futurism), which holds that past and present things exist but not future ones. The moving spotlight view suggests that all times exist but that the present is the only actual time. This view can be termed eternalist, but it preserves a non-perspectival difference between past, present, and future by treating tense as absolute. Additionally, the moving spotlight view retains some characteristics of presentism by maintaining that the ‘now’ is unique and privileged. -/- Broadly speaking, presentism is a common-sensical view, and so aligns with our manifest image of time. This view is, however, at odds with the scientific image of time. The primary motivation for eternalism arises from orthodox interpretations of the theories of relativity. According to them, simultaneity is relative, not absolute. This implies that there is no universal ‘now’ stretched out across the entire universe. One observer’s present can be another’s past or future. Assuming the universe is four-dimensional spacetime, then all events exist unconditionally. -/- The classical argument for eternalism was devised in the 1960s by Rietdijk in 1966 and Putnam in 1967, with subsequent follow-ups by Maxwell in 1985, Penrose in 1989, and Peterson and Silberstein in 2010. This argument and its ramifications remain the subject of ongoing debate. They shall be further explored in this entry, including their relation to other issues in the metaphysics of time and the philosophy of physics. (shrink)