This document collects discussion and commentary on issues raised in the workshop by its participants. Contributors are: Greg Frost-Arnold, David Harker, P. D. Magnus, John Manchak, John D. Norton, J. Brian Pitts, Kyle Stanford, Dana Tulodziecki.

This exploration of the global structure of spacetime within the context of general relativity examines the causal and singular structures of spacetime, revealing some of the curious possibilities that are compatible with the theory, such as `time travel' and `holes' of various types. Investigations into the epistemic and modal structures of spacetime highlight the difficulties in ruling out such possibilities, unlikely as they may seem at first. The upshot seems to be that what counts as a `physically reasonable' spacetime structure (...) in modern physics is far from clear. (shrink)

Here, we briefly review the notion of observational indistinguishability within the context of classical general relativity. We settle a conjecture given by Malament (1977) concerning the subject and then strengthen the result considerably. The upshot is this: There seems to be a robust sense in which the global structure of every cosmological model is underdetermined.

Cosmologists often use certain global properties to exclude "physically unreasonable" cosmological models from serious consideration. But, on what grounds should these properties be regarded as "physically unreasonable" if we cannot rule out, even with a robust type of inductive reasoning, the possibility of the properties obtaining in our own universe?

In this note, we cast doubt on the requirement of spacetime inextendibility; it is not at all clear that our universe is “as large as it can be.”.

A number of models of general relativity seem to contain “holes” that are thought to be “physically unreasonable.” One seeks a condition to rule out these models. We examine a number of possibilities already in use. We then introduce a new condition: epistemic hole-freeness. Epistemic hole-freeness is not just a new condition—it is new in kind. In particular, it does not presuppose a distinction between space-times that are “physically reasonable” and those that are not.

Here, we clarify the relationship among three space-time conditions of interest: geodesic completeness, hole-freeness, and inextendibility. In addition, we introduce a related fourth condition: effective completeness.

Here, we examine hole-freeness - a condition sometimes imposed to rule out seemingly artificial spacetimes. We show that under existing definitions (and contrary to claims made in the literature) there exist inextendible, globally hyperbolic spacetimes which fail to be hole-free. We then propose an updated formulation of the condition which enables us to show the intended result. We conclude with a few general remarks on the strength of the definition and then formulate a precise question which may be interpreted as: (...) Are all physically reasonable spacetimes hole-free? (shrink)

It has been argued that spacetime must be inextendible – that it must be “as large as it can be” in some sense. Here, we register some skepticism with respect to this position.

Gödel's remarks concerning the ideality of time are examined. In the literature, some of these remarks have been somewhat neglected while others have been heavily criticized. In this note, we propose a clear and defensible sense in which Gödel's work bears on the question of whether there is an objective lapse of time in our world.

We present a counterexample to Krasnikov's much discussed time machine no-go result. In addition, we prove a positive statement: a time machine existence theorem under a modest "no holes" assumption.

Here we briefly review the concept of "prediction" within the context of classical relativity theory. We prove a theorem asserting that one may predict one's own future only in a closed universe. We then question whether prediction is possible at all (even in closed universes). We note that interest in prediction has stemmed from considering the epistemological predicament of the observer. We argue that the definitions of prediction found thus far in the literature do not fully appreciate this predicament. We (...) propose a more adequate alternative and show that, under this definition, prediction is essentially impossible in general relativity. (shrink)

Malament-Hogarth spacetimes are the sort of models within general relativity that seem to allow for the possibility of supertasks. There are various ways in which these spacetimes might be considered physically problematic. Here, we examine these criticisms and investigate the prospect of escaping them.

Within the context of general relativity, we consider one definition of a “time machine” proposed by Earman, Smeenk, and Wüthrich. They conjecture that, under their definition, the class of time machine spacetimes is not empty. Here, we prove this conjecture. †To contact the author, please write to: Department of Philosophy, University of Washington, Box 353350, Seattle, WA 98195‐3350; e‐mail: manchak@uw.edu.

There is a venerable position in the philosophy of space and time that holds that the geometry of spacetime is conventional, provided one is willing to postulate a “universal force field.” Here we ask a more focused question, inspired by this literature: in the context of our best classical theories of space and time, if one understands “force” in the standard way, can one accommodate different geometries by postulating a new force field? We argue that the answer depends on one’s (...) theory. In Newtonian gravitation the answer is yes; in relativity theory, it is no. (shrink)

The hole argument purportedly shows that spacetime substantivalism implies a pernicious form of indeterminism. We show that the argument is seductive only because it mistakes a trivial claim (viz. there are isomorphic models) for a significant claim (viz. there are hole isomorphisms). We prove that the latter claim is false -- thereby closing the debate about whether substantivalism implies indeterminism.

It has been suggested by Clark Glymour that the spatio-temporal structure of the universe might be underdetermined by all observational data that could ever, theoretically, be gathered. It is possible for two spacetimes to be observationally indistinguishable (OI) yet topologically distinct. David Malament extended the argument for the underdetermination of spacetime structure by showing that under quite general conditions (such as the absence of any closed timelike curves) a spacetime will always have an OI counterpart (at least in weak sense). (...) Because the plight of the cosmologist seemed to be so discouraging in this regard, Malament considered the relationship between global properties and OI spacetimes. This information is helpful to the cosmologist. It allows, in principle, one to reject some spacetime models based on observational evidence. In this paper, I consider the relationship between variants of geodesic incompleteness and different senses (some old and some new) of OI. In light of the findings, it seems that (for the most part) the predicament of the cosmologist is not good. Quite generally, versions of geodesic incompleteness are not conserved even under the strongest formulations of OI. (shrink)

Non-collapse theories of quantum mechanics have the peculiar characteristic that, although their measurements produce definite results, their state vectors remain in a superposition of possible outcomes. David Albert has used this fact to show that the standard uncertainty relations can be violated if self-measurements are made. Bradley Monton, however, has held that Albert has not been careful enough in his treatment of self-measurement and that being more careful (considering mental state supervenience) implies no violation of the relations. In this paper, (...) I will outline both Albert's proposal and Monton's objections. Then, I will show how the uncertainty relations can be violated after all (even after being as careful as Monton). Finally, I will discuss how finding a way around the objections allows us to learn more about what is and what is not possible in non-collapse theories of quantum mechanics. (shrink)

Here, we show that one may "time travel" in Gödel spacetime with less total acceleration than was previously known. This answers a question posed by Malament.

Here we provide a proof that there exist closed timelike curves in Gödel spacetime with total acceleration less than 2π(9 + 6√3)^1/2. This answers a question posed by David Malament.

Here, we hypothesize that a smooth nongeodesic closed timelike curve is never most efficient with respect to total acceleration if a kink is permitted at the initial point. We support our hypothesis in a variety of ways. Most notably, we show Malament's opposing conjecture concerning Gödel space-time to be false.

There does not seem to be a consistent way to ground the concept of “force” in Cartesian first principles. In this article, I first review the literature on the subject. Then, I offer an alternative interpretation of force—one that seems to be coherent and consistent with Descartes’ project. Not only does the new position avoid the problems of previous interpretations, but it does so in such a way as to support and justify those previous interpretations. *Received June 2007; revised June (...) 2009. †To contact the author, please write to: Department of Philosophy, University of Washington, Box 353350, Seattle, WA 98195; e‐mail: manchak@uw.edu. (shrink)

Focused correlation compares the degree of association within an evidence set to the degree of association in that evidence set given that some hypothesis is true. Wheeler and Scheines have shown that a difference in incremental confirmation of two evidence sets is robustly tracked by a difference in their focus correlation. In this essay, we generalize that tracking result by allowing for evidence having unequal relevance to the hypothesis. Our result is robust as well, and we retain conditions for bidirectional (...) tracking between incremental confirmation measures and focused correlation. (shrink)

Here, formal tools are used to pose and answer several philosophical questions concerning space and time. The questions involve the properties of possible worlds allowed by the general theory of relativity. In particular, attention is given to various causal properties such as “determinism” and “time travel”.

Are theories ‘underdetermined by the evidence’ in any way that should worry the scientific realist? I argue that no convincing reason has been given for thinking so. A crucial distinction is drawn between data equivalence and empirical equivalence. Duhem showed that it is always possible to produce a data equivalent rival to any accepted scientific theory. But there is no reason to regard such a rival as equally well empirically supported and hence no threat to realism. Two theories are empirically (...) equivalent if they share all consequences expressed in purely observational vocabulary. This is a much stronger requirement than has hitherto been recognised— two such ‘rival’ theories must in fact agree on many claims that are clearly theoretical in nature. Given this, it is unclear how much of an impact on realism a demonstration that there is always an empirically equivalent ‘rival’ to any accepted theory would have—even if such a demonstration could be produced. Certainly in the case of the version of realism that I defend—structural realism—such a demonstration would have precisely no impact: two empirically equivalent theories are, according to structural realism, cognitively indistinguishable. (shrink)

Wilhelm (Forthcom Synth 199:6357–6369, 2021) has recently defended a criterion for comparing structure of mathematical objects, which he calls Subgroup. He argues that Subgroup is better than SYM \(^*\), another widely adopted criterion. We argue that this is mistaken; Subgroup is strictly worse than SYM \(^*\). We then formulate a new criterion that improves on both SYM \(^*\) and Subgroup, answering Wilhelm’s criticisms of SYM \(^*\) along the way. We conclude by arguing that no criterion that looks only to the (...) automorphisms of mathematical objects to compare their structure can be fully satisfactory. (shrink)

In his preface Mr Wilson writes 'I feel that a great many adults … would do better to spend less time in simply accepting the concepts of others uncritically, and more time in learning how to analyse concepts in general'. Mr Wilson starts by describing the techniques of conceptual analysis. He then gives examples of them in action by composing answers to specific questions and by criticism of quoted passages of argument. Chapter 3 sums up the importance of this kind (...) of mental activity. Chapter 4 presents selections for the reader to analyse, followed by questions of university entrance/scholarship type. This is a book to be worked through, in a sense a text-book. (shrink)

How do we acquire thoughts and beliefs about particulars by looking at pictures? One kind of reply essentially compares depiction to perception, holding that picture-perception is a form of remote object-perception. Lopes’s theory that pictures refer by demonstrative identification, and Walton’s transparency theory for photographs, constitute such remote acquaintance theories of depiction. The main purpose of this paper is to defend an alternative conception of pictures, on which they are not suitable for acquainting us with particulars but for acquainting us (...) with certain kinds of properties. This conception is outlined in §4, where it is argued that pictures are useful devices for what Heal has called indexical predication. In §2 and §3, I explain why I believe that remote acquaintance theories are false, and why picture-perception cannot function as a form of extended or remote object-perception. The main reason is that the contents of picture-perceptions do not themselves provide the kind of numerical and contextual information required for singular thought. Picture-reference is instead secured by independent beliefs or linguistic communication about the causal history of pictures as objects. In other words, it is beliefs about the numerical identity of pictures as objects that anchors the reference of the representational contents of pictures. (shrink)

Setting the scene -- Sentience and the sentient mind -- Special senses and their interpretation Survival strategies -- Social strategies -- Animals of the waters -- Animals of the air -- Animals of the savannah and plains -- Animals of the forests -- Close neighbours -- Our duty of care.

In this philosophically sophisticated and historically significant work, John H. Zammito reconstructs Kant's composition of The Critique of Judgment and reveals that it underwent three major transformations before publication. He shows that Kant not only made his "cognitive" turn, expanding the project from a "Critique of Taste" to a Critique of Judgment but he also made an "ethical" turn. This "ethical" turn was provoked by controversies in German philosophical and religious culture, in particular the writings of Johann Herder and (...) the Sturm und Drang movement in art and science, as well as the related pantheism controversy. Such topicality made the Third Critique pivotal in creating a "Kantian" movement in the 1790s, leading directly to German Idealism and Romanticism. The austerity and grandeur of Kant's philosophical writings sometimes make it hard to recognize them as the products of a historical individual situated in the particular constellation of his time and society. Here Kant emerges as a concrete historical figure struggling to preserve the achievements of cosmopolitan Aufkl-rung against challenges in natural science, religion, and politics in the late 1780s. More specifically Zammito suggests that Kant's Third Critique was animated throughout by a fierce personal rivalry with Herder and by a strong commitment to traditional Christian ideas of God and human moral freedom. "A work of extraordinary erudition. Zammito's study is both comprehensive and novel, connecting Kant's work with the aesthetic and religious controversies of the late eighteenth century. He seems to have read everything. I know of no comparable historical study of Kant's Third Critique."-Arnulf Zweig, translator and editor of Kant's ;IPhilosophical Correspondence, 1759-1799;X "An intricate, subtle, and exciting explanation of how Kant's thinking developed and adjusted to new challenges over the decade from the first edition of the Critique of Pure Reason to the appearance of the Critique of Judgment. "--John W. Burbidge, Review of Metaphysics "There has been for a long time a serious gap in English commentary on Kant's Critique of Judgment Zammito's book finally fills it. All students and scholars of Kant will want to consult it."--Frederick Beiser, Times Literary Supplement. (shrink)

We consider various curious features of general relativity, and relativistic field theory, in two spacetime dimensions. In particular, we discuss: the vanishing of the Einstein tensor; the failure of an initial-value formulation for vacuum spacetimes; the status of singularity theorems; the non-existence of a Newtonian limit; the status of the cosmological constant; and the character of matter fields, including perfect fluids and electromagnetic fields. We conclude with a discussion of what constrains our understanding of physics in different dimensions.

Obviously medicine should be evidence-based. The issues lie in the details: what exactly counts as evidence? Do certain kinds of evidence carry more weight than others? (And if so why?) And how exactly should medicine be based on evidence? When it comes to these details, the evidence-based medicine (EBM) movement has got itself into a mess – or so it will be argued. In order to start to resolve this mess, we need to go 'back to basics'; and that means (...) turning to the philosophy of science. The theory of evidence, or rather the logic of the interrelations between theory and evidence, has always been central to the philosophy of science – sometimes under the alias of the 'theory of confirmation'. When taken together with a little philosophical commonsense, this logic can help us move towards a position on evidence in medicine that is more sophisticated and defensible than anything that EBM has been able so far to supply. (shrink)

A supertask is a task that consists in infinitely many component steps, but which in some sense is completed in a finite amount of time. Supertasks were studied by the pre-Socratics and continue to be objects of interest to modern philosophers, logicians and physicists. The term “super-task” itself was coined by J.F. Thomson (1954). Here we begin with an overview of the analysis of supertasks and their mechanics. We then discuss the possibility of supertasks from the perspective of general relativity.

This book investigates the central role of reason in Islamic intellectual life. Despite widespread characterization of Islam as a system of belief based only on revelation, John Walbridge argues that rational methods, not fundamentalism, have characterized Islamic law, philosophy and education since the medieval period. His research demonstrates that this medieval Islamic rational tradition was opposed by both modernists and fundamentalists, resulting in a general collapse of traditional Islamic intellectual life and its replacement by more modern but far shallower (...) forms of thought. However, the resources of this Islamic scholarly tradition remain an integral part of the Islamic intellectual tradition and will prove vital to its revival. The future of Islam, Walbridge argues, will be marked by a return to rationalism"--Provided by publisher. (shrink)

One usually identifies a particular collection of geometric objects with the models of general relativity. But within this standard collection lurk ‘physically unreasonable’ models of spacetime. If such models are ruled out, attention can be restricted to some sub-collection of ‘physically reasonable’ models which can be considered a variant theory of general relativity. Since we have yet to identify a privileged sub-collection of ‘physically reasonable’ models, it is helpful to think of ‘general relativity’ in a pluralistic way; we can study (...) a collection of such ‘physically reasonable’ collections of models. (shrink)

This article shows a clear sense in which general relativity allows for a type of ‘machine’ that can bring about a spacetime structure suitable for the implementation of ‘supertasks’. 1Introduction2Preliminaries3Malament–Hogarth Spacetimes4Machines5Malament–Hogarth Machines6Conclusion.

Man controls and dominates the habitat of most animals, both domestic and wild and there is a need for a pragmatic, workable approach to the problem of reconciling animal welfare with economic forces and the needs of man. It is the author's contention that much of the current philosophical discussion of animal welfare is misdirected now that it is possible to measure to some extent what animals think and feel and how much they can appreciate their quality of life. The (...) book deals with farm animals, pets, wild animals and laboratory animals and dicusses their environmental requirements, fear and stress, their response to pain, injury, disease and death, behaviour and aggression, and the implications of biotechnology and genetic engineering. Finally, the book tries to reconcile reverence for life with the inescapability of killing and reviews the prospects of preserving and enhancing quality of life for animals through legislations, education, economic and moral incentives. (shrink)

John Turri gives an example that he thinks refutes what he takes to be “G. E. Moore's view” that omissive assertions such as “It is raining but I do not believe that it is raining” are “inherently ‘absurd'”. This is that of Ellie, an eliminativist who makes such assertions. Turri thinks that these are perfectly reasonable and not even absurd. Nor does she seem irrational if the sincerity of her assertion requires her to believe its content. A commissive counterpart (...) of Ellie is Di, a dialetheist who asserts or believes that The Russell set includes itself but I believe that it is not the case that the Russell set includes itself. Since any adequate explanation of Moore's paradox must handle commissive assertions and beliefs as well as omissive ones, it must deal with Di as well as engage Ellie. I give such an explanation. I argue that neither Ellie's assertion nor her belief is irrational yet both are absurd. Likewise neither Di's assertion nor her belief is irrational yet in contrast neither is absurd. I conclude that not all Moore-paradoxical assertions or beliefs are irrational and that the syntax of Moore's examples is not sufficient for the absurdity found in them. (shrink)

A brief account of educational aims, focussing on preparation for a life of autonomous well-being.