Philosophy and Phenomenological Research, Volume 104, Issue 1, Page 66-77, January 2022.

David Lewis famously defends a counterfactual theory of causation and a non-causal, similarity-based theory of counterfactuals. Lewis also famously defends the possibility of backward causation. I argue that this combination of views is untenable—given the possibility of backward causation, one ought to reject Lewis's theories of causation and counterfactuals.

The idea that some of God's past beliefs depend on our future actions has a long history, going back to Origen in the third century CE. However, it is not always clear what this idea amounts to, since it is not always clear what kind of dependence is at issue. This paper surveys five different interpretations of dependence and, in each case, considers the implications for the debate over theological fatalism. Along the way, we discuss a number of related issues, (...) including the nature of explanation, the scope of metaphysical grounding, and the possibility of backward causation. (shrink)

Kadri Vihvelin, in "What time travelers cannot do" (Philos Stud 81: 315-330, 1996), argued that "no time traveler can kill the baby who in fact is her younger self, because (V1) "if someone would fail to do something, no matter how hard or how many times she tried, then she cannot do it", and (V2) if a time traveler tried to kill her baby self, she would always fail. Theodore Sider (Philos Stud 110: 115-138, 2002) criticized Vihvelin's argument, and Ira (...) Kiourti (Philos Stud 139: 343-352, 2008) criticized both Vihvelin's argument and Sider's critique. I present a critique of Vihvelin's argument different from both Sider's and Kiourti's critiques: I argue in a novel way that both V1 and V2 are false. Since Vihvelin's argument might be understood as providing a challenge to the possibility of time travel, if my critique succeeds then time travel survives such a challenge unscathed. (shrink)

If time travel is possible, presumably so is my shooting my younger self ; then apparently I can kill him – I can commit retrosuicide. But if I were to kill him I would not exist to shoot him, so how can I kill him? The standard solution to this paradox understands ability as compossibility with the relevant facts and points to an equivocation about which facts are relevant: my killing YS is compossible with his proximity but not with his (...) survival, so I can kill him if facts like his survival are irrelevant but I cannot if they are relevant. I identify a lacuna in this solution, namely its reliance without argument on the hidden assumption that my killing YS is possible: if it is impossible, it is not compossible with anything. I argue that this lacuna is important, and I sketch a different solution to the paradox. (shrink)

A philosophical position may be characterized in different ways. Here we try to say how the naturalist answers certain . The questions come from very different areas; the spectrum of subjects is therefore quite mixed. There are, however, aspects of order: We start with (questions about) abstract subjects like logic, mathematics, metaphysics, then turn to problems of realism. And since in general naturalists are realists, the following questions on truth, laws of nature, origin of the universe, cosmology, evolution, body-mind-problem, freedom (...) of the will, religion, moral, and pseudoscience, are answered against a realistic background. German Eine philosophische Haltung kann man auf verschiedene Weisen charakterisieren. Hier versuchen wir zu sagen, wie der Naturalist auf bestimmte Kernfragen antwortet. Die Fragen stammen aus sehr verschiedenen Gebieten; das Themenspektrum ist deshalb recht bunt. Es gibt aber durchaus Ordnungsgesichtspunkte: Wir beginnen mit (Fragen zu) eher abstrakten Gegenständen wie Logik, Mathematik, Metaphysik, kommen dann zu Problemen des Realismus. Und da Naturalisten im Allgemeinen Realisten sind, werden die anschließenden Fragen über Wahrheit, Naturgesetze, Weltentstehung, Kosmologie, Evolution, Leib-Seele-Problem, Willensfreiheit, Religion, Moral und Pseudowissenschaften vor einem realistischen Hintergrund beantwortet. (shrink)

The traditional debate between compatibilists and incompatibilists was based on the assumption that if determinism deprives us of free will and moral responsibility, it does so by making it true that we can never do other than what we actually do. All parties to the debate took for granted the truth of a claim now widely known as "the principle of alternate possibilities": someone is morally responsible only if he could have done otherwise. In a famous paper, Harry Frankfurt argued (...) that the principle of alternate possibilities is false. I argue that Frankfurt's argument rests on a modal fallacy. (shrink)

I have argued that even if time travel is metaphysically possible, there are some things a time traveler would not be able to do. I reply here to critics who have argued that my account entails fatalism about the past or entails that the time traveler is unfree or that she is bound by “strange shackles.” My argument does not entail any sort of fatalism. The time traveler is able to do many of the things that everyone else can do (...) and is as free as any non-time-traveler. The time traveler is constrained only as we all are by the laws of nature. My argument shows only how strangely those constraints must operate if those laws permit time travel. (shrink)

Memories often come with a feeling of pastness. The events we remember strike us as having occurred in our past. What accounts for this feeling of pastness? In his recent book, Memory: A self-referential account, Jordi Fernández argues that the feeling of pastness cannot be grounded in an explicit representation of the pastness of the remembered event. Instead, he argues that the feeling of pastness is grounded in the self-referential causal content of memory. In this paper, I argue that this (...) account falls short. The representation of causal origin does not by itself ground a feeling of pastness. Instead, I argue that we can salvage the temporal localization account of the feeling of pastness by describing a form of egocentric temporal representation that avoids Fernández’s criticisms. (shrink)

Williamsonian modal epistemology is characterized by two commitments: realism about modality, and anti-exceptionalism about our modal knowledge. Williamson’s own counterfactual-based modal epistemology is the best known implementation of WME, but not the only option that is available. I sketch and defend an alternative implementation which takes our knowledge of metaphysical modality to arise, not from knowledge of counterfactuals, but from our knowledge of ordinary possibility statements of the form ‘x can F’. I defend this view against a criticism indicated in (...) Williamson’s own work, and argue that it is better connected to the semantics of modal language. (shrink)

Dispositions are modal properties. The standard conception of dispositions holds that each disposition is individuated by its stimulus condition(s) and its manifestation(s), and that their modality is best captured by some conditional construction that relates stimulus to manifestation as antecedent to consequent. I propose an alternative conception of dispositions: each disposition is individuated by its manifestation alone, and its modality is closest to that of possibility — a fragile vase, for instance, is one that can break easily. The view is (...) expounded in some detail and defended against the major objections. (shrink)

David Lewis’s counterpart theory is often seen as involving a radical departure from the standard, Kripke-style semantics for modal logic, suggesting that we are dealing with deeply divergent accounts of our modal talk. However, CT captures but one version of the relevant semantic intuition, and does so on the basis of metaphysical assumptions that are ostensibly discretionary. Just as ML can be translated into a language that quantifies explicitly over worlds, CT may be formulated as a semantic theory in which (...) world quantification is purely metalinguistic. And just as Kripke-style semantics is formally compatible with the doctrine of world-boundedness, a counterpart-based semantics may in principle allow for cases of trans-world identity. In fact, one may welcome a framework that is general enough to include both Lewis’s counterpart-based account and Kripke’s identity-based account as distinguished special cases. There are several ways of doing so. The purpose of this paper is to outline a fully general option and to illustrate its philosophical significance, showing how the large variety of intermediate relations that lie between Lewisian counterparthood and Kripkean identity yield a corresponding variety of modal theories that would otherwise remain uncharted. (shrink)

David Lewis’s analysis of “can” in “The Paradoxes of Time Travel” has been widely accepted both as a definitive analysis of “can” and as a successful resolution of the Grandfather Paradox for time travel. I argue that the central feature of his analysis puts it on all fours with a fallacy frequently imputed to fatalists such as Richard Taylor. I go on to consider two moves that might be made to avoid the fallacy, arguing that one of them leads to (...) the unavailability of an all-things-considered “can” and the other to a new primitive modality, not analyzable in Lewis’s way. (shrink)

This paper aims first, to introduce and elaborate upon a certain principle about being (existence), roughly, that once something exists or has being, it cannot lose it: what is cannot, in this sense, unbe; and second, to apply this principle to a well-known issue in the philosophy of time, viz., that of whether future events, like past events, though of course not now occurring, nonetheless have being.

This article is about time. It is about time, or more precisely, about the absence of time in law’s digital future. It is also about time travelling and the seemingly ever-popular BBC science fiction television series Doctor Who. Further, it is about law’s timefullness; about law’s pictorial past and the ‘visual baroque’ of its chronological fused future. Ultimately, it is about a time paradox of seeing time run to a time when time runs ‘No More!’ This ‘timey-wimey’ article is in (...) three parts. The first part looks to a hazy remembered past of the legal emblem tradition as presented in Peter Goodrich’s Legal Emblems and the Art of Law to learn visual literacy and also to glimpse the essential elements of modern legality with authority, decision and violence. The second part maps how these images and icons of modern legality are manifest in the Doctor Who fiftieth year anniversary special ‘The Day of the Doctor.’ The third stage looks beyond these first order meanings to understand the chronological chaos of ‘The Day of the Doctor.’ The technicity of the image as a portal through time and space that the narrative revolves around charts the implications for the digital end of time for law. (shrink)

I argue that, contrary to an idea to be found in popularizations of time travel, one cannot more easily multiply oneself by taking younger versions of oneself back in time than by travelling back in time on one’s own. The reason is that the suggested multiplication of the traveller is, from a global perspective, only apparent.

I criticize Lockwood’s solution to the “paradoxes” of time travel, thus endorsing Lewis’s more conservative position. Lockwood argues that only in the context of a 5D space-time-actuality manifold is the possibility of time travel compatible with the Autonomy Principle (according to which global constraints cannot override what is physically possible locally). I argue that shifting from 4D space-time to 5D space-time-actuality does not change the situation with respect to the Autonomy Principle, since the shift does not allow us to have (...) a coincidence-free local dynamical theory. (shrink)

In this essay, my goal is, first, to describe the most important contemporary philosophical approaches to the nature of time, and then, secondly, to discuss the ways in which those different accounts bear upon the question of the possibility of divine foreknowledge. I shall argue that different accounts of the nature of time give rise to different objections to the idea of divine foreknowledge, but that, in addition, there is a general argument for the impossibility of divine foreknowledge that is (...) independent of one’s account of the nature of time. (shrink)

There is a longstanding argument that purports to show that divine foreknowledge is inconsistent with human freedom to do otherwise. Proponents of this argument, however, have for some time been met with the following reply: the argument posits what would have to be a mysterious non-causal constraint on freedom. In this paper, I argue that this objection is misguided – not because after all there can indeed be non-causal constraints on freedom (as in Pike, Fischer, and Hunt), but because the (...) success of the incompatibilist's argument does not require the real possibility of non-causal constraints on freedom. I contend that the incompatibilist's argument is best seen as showing that, given divine foreknowledge, something makes one unfree – and that this something is most plausibly identified, not with the foreknowledge itself, but with the causally deterministic factors that would have to be in place in order for there to be infallible foreknowledge in the first place. (shrink)

Nonreductive physicalism faces serious problems regarding causal exclusion, causal heterogeneity, and the nature of realization. In this paper I advance solutions to each of those problems. The proposed solutions all depend crucially on embracing modal counterpart theory. Hence, the paper’s thesis: counterpart theory saves nonreductive physicalism. I take as my inspiration the view that mental tokens are constituted by physical tokens in the same way statues are constituted by lumps of clay. I break from other philosophers who have pursued this (...) line, however, in that I hold that constitution is identity. Much of the value of the comparison to statues and lumps is that it calls to mind the resources used to defend constitution-as-identity, most notably that of counterpart theory. Along the way, I discuss the virtues of a trope ontology, modal objections to token identity theories, the prospects of conditional analyses of causal powers, the subset account of realization, and the grounding problem. I also endorse a novel, empirical argument in favor of counterpart theory. (shrink)

Many philosophers maintain that the ability to do otherwise is compatible with comprehensive divine foreknowledge but incompatible with the truth of causal determinism. But the Fixity of the Past principle underlying the rejection of compatibilism about the ability to do otherwise and determinism appears to generate an argument also for the incompatibility of the ability to do otherwise and divine foreknowledge. By developing an account of ability that appeals to the notion of explanatory dependence, we can replace the Fixity of (...) the Past with a principle that does not generate this difficulty. I develop such an account and defend it from objections. I also explore some of the account's implications, including whether the account is consistent with presentism. (shrink)

It is widely assumed that sense perception cannot deliver knowledge of nonactual (metaphysical) possibilities. We are not supposed to be able to know that a proposition p is necessary or that p is possible (if p is false) by sense perception. This paper aims to establish that the role of sense perception is not so limited. It argues that we can know lots of modal facts by perception. While the most straightforward examples concern possibility and contingency, others concern necessity and (...) impossibility. The possibility of a perceptual route to some modal knowledge is not as radical as it may at first sound. On the contrary, acknowledging it has benefits. (shrink)

Personal identity theory has become increasingly sensitive to the importance of the first-person perspective. However, certain ways of speaking about that perspective do not allow the full temporal aspects of first-person perspectives on the self to come into view. In this paper I consider two recent phenomenologically-informed discussions of personal identity that end up yielding metaphysically divergent views of the self: those of Barry Dainton and Galen Strawson. I argue that when we take a properly temporally indexical view of the (...) first-person perspective, and thereby resist the assumption that phenomenally-figured and theoretically-figured identity claims must have a common object, the metaphysically awkward accommodations each of these authors is compelled to make cease to be necessary. (shrink)

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. (shrink)

The Principle of Alternative Possibilities is the intuitive idea that someone is morally responsible for an action only if she could have done otherwise. Harry Frankfurt has famously presented putative counterexamples to this intuitive principle. In this paper, I formulate a simple version of the Principle of Alternative Possibilities that invokes a course-grained notion of actions. After warming up with a Frankfurt-Style Counterexample to this principle, I introduce a new kind of counterexample based on the possibility of time travel. At (...) the end of the paper, I formulate a more sophisticated version of the Principle of Alternative Possibilities that invokes a certain fine grained notion of actions. I then explain how this new kind of counterexample can be augmented to show that even the more sophisticated principle is false. (shrink)

According to a widely held principle—the poss-ability principle—an agent, S, is able to only if it is metaphysically possible for S to. I argue against the poss-ability principle by developing a novel class of counterexamples. I then argue that the consequences of rejecting the poss-ability principle are interesting and far-reaching.

The concepts of philosophy and imaginative literature have unclear boundaries and blurred edges; they can hardly be defined essentially in any fruitful manner. But we can talk of indicators of a text being philosophical or literary. The concepts of philosophy and literature are contestable. Further, there are no clear‐cut signs of cognitive progress in philosophy and literature. It is also far from certain that there are any philosophical or literary truths. Actually, works of philosophy and literature deal more in possibilities (...) than in actualities. In addition, fictional narratives play an important role in both philosophical and literary texts. Moreover, philosophy and literature share a tendency to thematize themselves, reflect on themselves. If, however, argumentation were to disappear entirely from all philosophical texts, while every literary text is dominated by argumentative discourse, then the concepts of literature and philosophy would become almost devoid of content. Despite this, there is no gap between philosophy and imaginative literature. (shrink)

My task here is the first one. I do present a consistent formal system and claim that it provides a perfect model of natural languages such as English, but this system involves no surprises. It is none other than the standard framework of classical logic and model theory. The real weight of the argument lies in the claim that the classical framework—without alteration or addition—contains the resources to model what happens when we say in English ‘This sentence is not true’.

This paper addresses a worry about backwards time travel. The worry is that there is something mysteriously inexplicable about the combination of commonplace events that will inevitably conspire to prevent the time traveler from doing something impossible such as killing her younger self. The worry is first distinguished from other problems for backwards time travel concerning its alleged impossibility or improbability. It is then shown that the worry is misplaced: there is in fact no real problem here. Yet the worry (...) has been widely expressed—so a suggestion is also made as to why it is so easy to get into the position of thinking that there is a genuine problem here, when in fact there is not. Finally, in light of the resolution of the inexplicability worry, a new way of dealing with the other two problems for backwards time travel—concerning its alleged impossibility and improbability—is proposed. (shrink)

This paper argues that the most famous objection to backward time travel can carry no weight. In its classic form, the objection is that backward time travel entails the occurrence of impossible things, such as auto-infanticide—and hence is itself impossible. David Lewis has rebutted the classic version of the objection: auto-infanticide is prevented by coincidences, such as time travellers slipping on banana peels as they attempt to murder their younger selves. I focus on Paul Horwich‘s more recent version of the (...) objection, according to which backward time travel entails not impossible things, but improbable ones—such as the string of slips on banana peels that would be required to stop a determined auto-infanticidal maniac from murdering her younger self—and hence is itself highly improbable. I argue that backward time travel does not entail unusual numbers of coincidences; and that, even if it did, that would not render its occurrence unlikely. (shrink)

Though everyday life accords a great deal of significance to practical abilities—such as the ability to walk, to speak French, to play the piano—philosophers of action pay surprisingly little attention to them. By contrast, abilities are discussed in various other philosophical projects. From these discussions, a partial theory of abilities emerges. If the partial theory—which is at best adequate only to a few examples of practical abilities—were correct, then philosophers of action would be right to ignore practical abilities, because they (...) could play no fundamental role in an account of human agency. For the idea that practical abilities *do* play a fundamental role in human agency to be worth considering, an alternative conception of them is needed. As a first step, I attempt some of the necessary ground-clearing work. (shrink)

The doctrine of the immaculate conception, which is a dogma binding on all Roman Catholics and also held by members of some other Christian denominations, holds that Mary the mother of Jesus Christ was conceived without the stain of original sin as a result of the redeeming effects of Christ’s later life, passion, death, and resurrection. In this paper I argue first that, even on an orthodox reading of this doctrine, the immaculate conception seems to result in a kind of (...) causal time loop. I then consider several common philosophical objections to causal time loops, showing how each is either not a serious problem for causal time loops in general or is not a serious problem for the immaculate conception time loop in particular because of some particular features of that particular loop. The upshot of this discussion is that it shows that anyone who is committed to the dogma of the immaculate conception is also committed to the possibility, and, indeed, the actuality, of at least one causal time loop, but also that this is no reason to reject the dogma, since all of the major worries for causal time loops can be resolved in one way or another. (shrink)

[Significantly updated in Chapter 7 of Awareness and the Substructure of Knowledge] Many have found it plausible that knowledge is a constitutively normative state, i.e. a state that is grounded in the possession of reasons. Many have also found it plausible that certain cases of proprioceptive knowledge, memorial knowledge, and self-evident knowledge are cases of knowledge that are not grounded in the possession of reasons. I refer to these as cases of basic knowledge. The existence of basic knowledge forms a (...) primary objection to the idea that knowledge is a constitutively normative state. In what follows I offer a way through the apparent dilemma of having to choose between either basic knowledge or the normativity of knowledge. The solution involves homing in on a state of awareness (≈non-accidental true representation) that is distinct from knowledge and which in turn grounds the normativity of knowledge in a way that is fully consistent with the existence of basic knowledge. An upshot of this is that externalist theories of knowledge turn out to be fully compatible with the thesis that knowledgeable beliefs are always beliefs that are justified by the reasons one possesses. (shrink)

In no possible world does a time traveler succeed in killing herearlier self before she ever enters a time machine. So if many,many time travelers went back in time trying to kill theirunprotected former selves, the time travelers would fail inmany strange, coincidental ways, slipping on bananapeels, killing the wrong victim, and so on. Such cases producedoubts about time travel. How could ``coincidences'' beguaranteed to happen? And wouldn't the certainty of coincidentalfailure imply that time travelers are not free to killtheir (...) earlier selves? But if so, what would inhibit theirfreedom? Despite initial appearances, these and other doubtsmay be answered: the possibility of time travel survives yetanother challenge. (shrink)

Some say that presentism precludes time travel into the past since it implies that the past does not exist, but this is a bad argument. Presentism says that only currently existing entities exist, and that the only properties and relations those entities instantiate are those that they currently instantiate. This does in a sense imply that the past does not exist. But if that precluded time travel into the past, it would also preclude the one-second-per-second “time travel” into the future (...) that is ordinary persistence, for presentism accords the future the same ontological status as the past. Instead of quantifying over past and future objects and events, presentists speak a tensed language, regimented with primitive sentential tense operators. For a presentist, a persisting person is one who did exist, and who will exist. Regimented, these claims become: it was the case that she exists, and it will be the case that she exists. The presentist may then apply the same strategy to time travel proper. Suppose Katy travels back to the time of the dinosaurs. The presentist can say that it was the case two hundred million years ago that Katy exists. This claim, which consists of a present-tense statement “Katy exists” embedded within the past tense operator it was the case two hundred million years ago that, is exactly the sort of statement about time that a presentist is free to accept. This has all been made clear by Simon Keller and Michael Nelson ( ). In addition to rebutting the bad argument against the consistency of presentism and time travel, Keller and Nelson argue positively in favor of consistency by showing how to translate David Lewis’s ( ) account of time travel into the presentist’s tensed language. The appearance of con ict between presentism and time travel, they argue, is due only to the fact that most defenders of time travel (for example Lewis) have tended to phrase their defenses in nonpresentist terms. As much as I applaud their rebuttal of the bad argument, I wish to sound a note of caution.. (shrink)

I thank my commentators for their kind words, and for their close reading and challenging criticisms of my book. I have chosen selective and substantive replies. Those criticisms I ignore, I ignore because I have little more to say, not because they are unworthy of discussion.

Analytic Philosophy, Volume 62, Issue 3, Page 275-294, September 2021.

How should rational beliefs change over time? The standard Bayesian answer is: by conditionalization (a.k.a. Bayes’ Rule). But conditionalization is not an adequate rule for updating beliefs in “centred” propositions whose truth-value may itself change over time. In response, some have suggested that the objects of belief must be uncentred; others have suggested that beliefs in centred propositions are not subject to diachronic norms. Iargue that these views do not offer a satisfactory account of self-locating beliefs and their dynamics. A (...) third response is to replace conditionalization by a new norm that can deal with centred propositions. I critically survey anumber of new norms that have been proposed, and defend one particular approach. (shrink)

A famous puzzle called “Grandmother Paradox” is used to argue against the feasibility of traveling backward in time because of the logical and nomological problems such travel involves, and not only because we don’t have the technology to make it reality. The same kind of problems would be encountered in leaping forward in time and then returning to the time of departure. We argue that a similar family of problems also arise in our having foreknowledge of the future without making (...) any time travel. We point to the mysterious consequences of having access to a being, say a machine or a psychic, that can have infallible knowledge of the future and conveys this foreknowledge to human beings truthfully, without any lies or distortions. The cause of these mysterious consequences is the fact that such machines or psychics will raise logical and nomological complications reminiscent of the ones we encounter in time travel scenarios, and that is a strong reason why infallible foretellers cannot exist. We conclude that we can have foreknowledge of the future, in principle, only within certain narrow limits, if at all. (shrink)

It is sometimes argued that there is an analogy between time and modality: What is true of time, mutatis mutandis, should be true of modality, and vice versa. However, I think that the importance of this analogy has not been truly appreciated in the literature. In this paper, I try to offer a plausible account of the relationship between time and modality based on what is known as presentist ersatzism. If the attempt succeeds, it will be shown that ersatzists about (...) time are better able to explain what possible worlds are. (shrink)

In a series of recent papers, Saul Smilansky has argued that compatibilists have no principled way of resisting the view that prepunishment is at least sometimes appropriate, thus revealing compatibilism to be a radical position, out of keeping with our ordinary moral judgments. Recent attempts to resist this conclusion seem to have overlooked the biggest problem with Smilansky’s argument, which is this: Smilanksy argues that the most obvious objection to prepunishment—namely, that it is inappropriate because it involves punishing the innocent (...) for crimes they have not committed—is unavailable to compatibilists. If compatibilism is true, he says, then if it is causally determined that someone is going to commit a crime, the fact that one has not yet done so is a mere temporal matter bearing no moral significance. I argue that there is no reason for compatibilists to accept this point. Compatibilists can (and should) resist Smilansky's claim that one’s not yet having committed a crime is morally insignificant and so resist the temptation to prepunish. (shrink)

It is not uncommon in time travel stories to find that the mechanism by which the time travel is achieved is not invented. A time traveller could journey to his/her own past and give the designs of the time travel machine to his/her earlier self as s/he was given the designs as a younger person. These designs never get thought up by anyone. Such a situation would conflict with the usual conception of the acquisition of knowledge. This situation is called (...) the Temporal Epistemic Anomaly and would arise if knowledge is gained at a time prior to the information in question being transmitted but is not discovered or invented at any time. This article examines the implications of information propagating around a causal chain that is closed in time (which is required to create the Anomaly) and whether this information need have a specific origin point. (shrink)

In 1987, Roy Sorensen coined the term 'parahistory' to denote the study of genuinely anachronistic artefacts delivered by time travel.¹ 'Parahistory' would thus stand to history rather as parapsychology is claimed to stand to psychology, i.e. the parahistorian would study historical data that were obtained through channels that orthodox science does not recognise. How might one establish credentials as a time traveller? What sort of evidence could a time-traveller point to in support of claims that would presumably command a great (...) deal of scepticism? While successful predictions might be one confirmatory tool, supporting evidence needn't take the form of predictions. (Although Sorensen offers an intriguing argument that a Humean about miracle-testimony would be obliged to reject any testimony to the occurrence of time travel.) Perhaps artefacts that time travellers retrieve from other times (past or future) could usefully supplement testimonial or predictive evidence for the parahistorian. However, this paper will argue, any appeal to past-artefactual evidence for parahistorical claims faces a dilemma that threatens to undermine its value: appeals to past-artefact evidence must either collapse into appeals to predictive evidence or see their value diminished by such past artefacts' necessarily exhibiting contradictory indicators of age and period. (shrink)