In this paper I defend the compossibility of presentism and time travel from two objections. One objection is that the presentist’s model of time leaves nowhere to travel to; the second objection attempts to equate presentist time travel with suicide. After targeting some misplaced scrutiny of the first objection, I show that presentists have the resources to account for the facts that make for time travel on the traditional Lewisian view. In light of this ability, I argue that both of (...) the objections fail. (shrink)

The quality of a life is typically understood as a function of the actual goods and bads in it, that is, its actual value. Likewise, the value of a population is typically taken to be a function of the actual value of the lives in it. We introduce an alternative understanding of life quality: adjusted value. A life’s adjusted value is a function of its actual value and its ideal value (the best value it could have had). The concept of (...) adjusted value is useful for at least three reasons. First, it fits our judgments about how well lives are going. Second, it allows us to avoid what we call False Equivalence, an error related to the non-identity problem. Third, when we use adjusted value as an input for calculating the value of a population, we can avoid two puzzles that Derek Parfit calls the “Repugnant Conclusion” and the “Mere Addition Paradox.”. (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)

Sometimes also called retro causation. A common feature of our world seems to be that in all cases of causation, the cause and the effect are placed in time so that the cause precedes its effect temporally. Our normal understanding of causation assumes this feature to such a degree that we intuitively have great difficulty imagining things differently. The notion of backward causation, however, stands for the idea that the temporal order of cause and effect is a mere contingent feature (...) and that there may be cases where the cause is causally prior to its effect but where the temporal order of the cause and effect is reversed with respect to normal causation, i.e. there may be cases where the effect temporally, but not causally, precedes its cause. (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)

The standard definition of an instantaneous temporal part cannot properly deal with cases involving time travel. This paper provides a new definition of an instantaneous temporal part by appealing to David Lewis's distinction between external time and personal time. The new definition avoids the problems because it does not allow more than one instantaneous temporal part of an object at each moment of its personal time. We argue that this new definition, combined with our new perdurantist semantic thesis, deals with (...) cases of time travel successfully. (shrink)

Lucy O'Brien has argued that defenders of the object-dependence of singular thought should attend to mental agency. A recent trend in action theory, towards what John Maier calls ‘agentive modality’, suggests that we conceive agency in terms of the exercise of abilities, and this is how I propose to approach O'Brien's challenge. For Gareth Evans, an early defender of object-dependence, maintained that thinking is the exercise of a complex of abilities. The debate about object-dependence gives way to the question whether (...) we have what I call dedicated singular mental abilities. In arguing that we do, I defend the thesis of object-dependence. (shrink)

Philosophy and Phenomenological Research, EarlyView.

We argue that explanations appealing to logical impossibilities are genuine explanations. Our defense is based on a certain picture of impossibility. Namely, that there are impossibilities and that the impossibilities have structure. Assuming this broad picture of impossibility we defend the genuineness of explanations that appeal to logical impossibilities against three objections. First, that such explanations are at odds with the perceived conceptual connection between explanation and counterfactual dependence. Second, that there are no genuinely contrastive why-questions that involve logical impossibilities (...) and, third, that explanations appealing to logical impossibilities rule nothing out. (shrink)

Michael Tooley’s latest argument against the possibility of divine foreknowledge trades on the idea that, whichever theory of time is true, the ontology of the future—or lack thereof—gives rise to special problems for God’s prescience. I argue that Tooley’s reasoning is predicated on two mischaracterizations and conclude that, on at least some theories of time, the possibility of divine foreknowledge appears secure.

_ Paradoxes of Time Travel _ By WassermanRyanOxford University Press, 2018. x + 250 pp.

In his paper, The Paradoxes of Time Travel, David Lewis posits a defense for the possibility of time travel by arguing that the grandfather 'paradox' is not, in fact, paradoxical at all. Two alternative solutions to the grandfather paradox are discussed in this paper. The first is a result of Paul Horwich’s reply to Lewis and aims to pit the Lewisian conception of compatibility against Horwich’s improbability defense. Proposed by Nicholas Smith and C.G. Goddu, this theory explains that any attempt (...) at backward time travel will lead to the creation of long strings of improbable coincidences. An alternative thesis of the multiverse is also discussed, wherein it was proposed that instead of traveling into his past, the time traveler enters an alternate, yet completely identical universe. The multiverse thesis did not stand up to any philosophical critique, and it was posited that the thesis changes the nature of the question entirely. It is evident that Lewis’ discussion of the grandfather paradox raises several fundamentally interesting philosophical questions regarding the logical and causal irregularities of changing the past. This paper aims to adress some of these questions through a metaphysical analysis of Lewis' view, backwards causality, and the nature of time itself. (shrink)

ABSTRACT In 'An Insoluble Problem', Storrs McCall presents an argument which he takes to reveal the real problem with backwards time travel. McCall asks us to imagine a scenario in which a renowned artist produces his famous works by copying them from reproductions brought back to him by a time-travelling art critic. The novelty of the scenario lies in its introduction of aesthetic constraints on the possibility of time travel, something which sets it apart from other time travel cases. McCall (...) states that 'The puzzle lies... in finding where artistic creativity enters the equation', and that 'Unlike the traditional "paradoxes of time travel", this problem has no solution'. We offer four responses to McCall's puzzle. Whilst we show that the puzzle is not insoluble, we also argue that it reveals something about the proper relationship between copying and creativity, which may not have been apparent without considering time travel. (shrink)

A decision theory can be useful not only as a tool for determining which action, given your desires and beliefs, is most preferable, but also as a means for analyzing the nature of rational deliberation. In this paper, I turn to two classic proposals for a causal decision theory, that of Lewis and that of Sobel :407–437, 1986. doi: 10.1080/00048408612342621). As Rabinowicz revealed, Lewis’ proposal is unable to be applied to as broad a set of decision problems as a version (...) of CDT offered by Sobel, an account of decision theory that Lewis thought was equivalent to his own. Rabinowicz argued by offering a counterexample to Lewis’ account. In this essay, I build on that approach, offering a novel counterexample, the “Faulty Signal Problem,” which proves that Lewis’ theory fails to provide a recommendation in an even broader class decision problems than Rabinowicz recognized, particularly those that exhibit what I refer to as counterfactual asymmetries. The problem for Lewis, however, is not just a technicality. Lewis and Sobel’s theories, respectively, conceptualize rational deliberation in two different ways. Lewis’ proposal, which utilized conditionalization as its form of belief revision, shares with evidential decision theory the same underlying attitude toward the agent as evidence-maker. In contrast, Sobel’s theory, based on imaging, captures the idea that deliberation requires a distinctly suppositional attitude that respects the agent’s causal views. The Faulty Signal Problem not only gives reason to favor Sobel’s proposal over Lewis’; it also provides justification for seeing imaging as necessary for a genuinely causal decision theory. (shrink)

A world in which time travel into the past occurred would seem like a most strange world. Nicholas Smith, however, in his ‘Bananas Enough for Time Travel’, argues that time travel is not so strange as we think. In particular, he argues against what he views as the main reason time travel worlds seem so strange – the claim that time travel entails unusual numbers of coincidences. I shall argue that Smith's argument for rejecting the claim is inadequate. Hence, the (...) debate over the consequences of the coincidences of time travel cannot be avoided by denying the coincidences themselves. (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)

The possibility of continuous backwards time travel—time travel for which the traveler follows a continuous path through space between departure and arrival—gives rise to the double-occupancy problem. The trouble is that the time traveler seems bound to have to travel through his or her younger self as the trip begins. Dowe and Le Poidevin agree that this problem is solved by putting the traveler in motion for a gradual trip to the past. Le Poidevin goes on to argue, however, that (...) the gradual trip gives rise to the Cheshire cat problem, a concern about whether the traveler survives the gradual trip. We address the Cheshire cat problem by proposing and considering new continuity constraints on identity over time. Along the way, we come upon an endurantist conception of temporal parts. (shrink)

The Multiverse Thesis is a proposed solution to the Grandfather Paradox. It is popular and well promulgated, found in fiction, philosophy and (most importantly) physics. I first offer a short explanation on behalf of its advocates as to why it qualifies as a theory of time travel (as opposed to mere 'universe hopping'). Then I argue that the thesis nevertheless has an unwelcome consequence: that extended objects cannot travel in time. Whilst this does not demonstrate that the Multiverse Thesis is (...) false, the consequence should give pause for concern. Even if it does not lead one to reject the thesis, I briefly detail some reasons to think it is interesting nonetheless. (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)

Endurantism, as opposed to perdurantism, is supposed to be the intuitive view. But the ‘endurantist intuition’ – roughly, that objects persist through time by being numerically identical and wholly located at all times at which they exist – is behind more than just endurantism. Indeed, it plays an important role in the motivation of some theories about the passage of time, and some theories about the nature of the subject. As we shall see, the endurantist intuition is often taken in (...) these cases to be a reason, or at least a motivation, to endorse one or the other of these metaphysical theories. Sometimes, it is even said to constitute a basis for an argument in their favour. In this article, I show that such an appeal to this ‘endurantist intuition’ is misleading and wrong. I do not deny that there is an intuition of this kind, but I deny that it can play any philosophically significant role as a reason – and even less as a basis for an argument – in defending metaphysical theories such as endurantism, dualism, or the A-theory. (shrink)

The compatibilism debate revolves around the question whether moral responsibility and free will are compatible with determinism. Prima facie, this seems to be a substantial issue. But according to the triviality objection, the disagreement is merely verbal: compatibilists and incompatibilists, it is maintained, are talking past each other, since they use the terms “free will” and “moral responsibility” in different senses. In this paper I argue, first, that the triviality objection is indeed a formidable one and that the standard replies (...) to it are unconvincing. This, however, does not mean that the objection succeeds. Starting with the debate about moral responsibility, I attempt to show that there is an account of moral responsibility which enables us to defend the compatibilism debate against the charge of triviality—namely, the normative conception of moral responsibility. If “moral responsibility” is defined in normative terms, then we cannot distinguish between a compatibilist and an incompatibilist sense of “moral responsibility”, because such a disambiguation would be inconsistent with the essential action-guiding force of normative expressions. Finally, I examine how the normative conception of moral responsibility can help us to defend the free will debate against the triviality objection and draw some general conclusions. (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 claimed that unacceptable constraints on initial data are imposed by certain responses to paradoxes that threaten time travel, closed timelike curves (CTCs) and other backwards causation hypotheses. In this paper I argue against the following claims: to say “contradictions are impossible so something must prevent the paradox” commits in general to constraints on initial data, that for fixed point dynamics so-called grey state solutions explain why contradictions do not arise, and the latter have been proved to avoid constraints (...) on initial data. †To contact the author, please write to: Philosophy, University of Queensland, Brisbane, Queensland 4072, Australia; e-mail: [email protected]. (shrink)

It is often thought that presentism is incompatible with time travel. I will argue that this common view is incorrect. Specifically, I will argue that presentism is compatible with some stories that involve closed timelike curves, and that some of these stories are time-travel stories.

Dummett and others have failed to show that an effect can precede its cause. Dummett claimed that 'backwards causation' is unproblematic in agentless worlds, and tried to show under what conditions it is rational to believe that even backwards agent-causation occurs. Relying on considerations originating in discussions of special relativity, I show that the latter conditions actually support the view that backwards agent-causation is impossible. I next show that in Dummett's agentless worlds explanation does not necessitate backwards causation. I then (...) show why even relative backwards causation is impossible in his and Tooley's scenarios of parallel processes in which causes apparently act in opposite temporal directions. We thus have good reasons for thinking that backwards causation is impossible. (shrink)

In this paper, I raise a novel objection to David Lewis’s Humean account of laws. The objection is that non-universal laws are metaphysically possible, but Lewis’s account cannot accommodate them. I then propose and defend an extension of Lewis’s view that gives us an account of Humean non-universal laws.

A plausible thought is that we should evaluate counterfactuals in the actual world by holding the present ‘fixed’; the state of the counterfactual world at the time of the antecedent, outside the area of the antecedent, is required to match that of the actual world. When used to evaluate counterfactuals in the actual world, this requirement may produce reasonable results. However, the requirement is deeply problematic when used in the context of explaining causal asymmetry. The requirement plays a crucial role (...) in certain statistical mechanical explanations of the temporal asymmetry of causation. I will use a case of backwards time travel to show how the requirement enforces certain features of counterfactual structure a priori. For this reason, the requirement cannot be part of a completely general method of evaluating counterfactuals. More importantly, the way the requirement enforces features of counterfactual structure prevents counterfactual structure being derived from more fundamental physical structure—as explanations of causal asymmetry demand. Therefore, the requirement cannot be used when explaining causal asymmetry. To explain causal asymmetry, we need more temporally neutral methods for evaluating counterfactuals—those that produce the right results in cases involving backwards time travel, as well as in the actual world. (shrink)

Time travel, it has been argued, leads to paradoxes, and in particular to a problem known as the grandfather paradox. Lewis has famously argued for the now standard view that the grandfather paradox is merely apparent. But underlying Lewis's solution is a faulty account of ability statements – one, according to which ability statements express possibility statements. I argue, contrary to Vihvelin and others, that an ameliorated view of ability statements allows for the same treatment of the seeming paradox. Hence, (...) Lewis's take on the grandfather paradox stands despite the failure of the particular view of ability statements it is built upon. (shrink)

La philosophie contemporaine du temps voit s’affronter deux conceptions du temps : celle du devenir qui identifie la réalité naturelle à un présent en constant renouvellement et celle de l’univers-bloc qui assimile la réalité naturelle à un espace-temps étendu dans quatre dimensions. Cette dernière approche implique notamment que les événements qui nous semblent passés et futurs sont tout aussi réels que les événements présents et que les êtres humains, bien que mortels, sont des êtres éternels. L’auteur défend cette théorie de (...) l’univers-bloc en montrant que le raisonnement philosophique et les avancées les plus récentes de la physique contemporaine s’accordent à montrer que ce monde quadri-dimensionnel est bel et bien le nôtre. (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)

Must space be a unity? This question, which exercised Aristotle, Descartes and Kant, is a specific instance of a more general one; namely, can the topology of physical space change with time? In this paper we show how the discussion of the unity of space has been altered but survives in contemporary research in theoretical physics. With a pedagogical review of the role played by the Euler characteristic in the mathematics of relativistic spacetimes, we explain how classical general relativity (modulo (...) considerations about energy conditions) allows virtually unrestrained spatial topology change in four dimensions. We also survey the situation in many other dimensions of interest. However, topology change comes with a cost: a famous theorem by Robert Geroch shows that, for many interesting types of such change, transitions of spatial topology imply the existence of closed timelike curves or temporal non-orientability. Ways of living with this theorem and of evading it are discussed. (shrink)

In a recent paper in this journal, McCall and Lowe (2003) argue that an understanding of Special Relativity reveals that the A theorist’s notion of temporal passage is consistent with the B theory of time. They arrive at this conclusion by considering the twins’ paradox, where one of two twins (T) travels to Alpha Centauri and back and upon her return has aged 30 years, while her earth-bound twin (S) has aged 40 years.Does this reconcile the A theoretic notion of (...) temporal passage with the B theory of time? I argue not. (shrink)

As the past-future asymmetry – that fact that we have records of the past but not the future – is still a puzzle the aim of this paper is twofold: a) to explain the asymmetry and its status in philosophy and physics and to critically review the proposed solutions to this puzzle; b) to advance a dynamic solution to the puzzle in terms of the ‘universality’ of the entropy relation in statistical mechanics.

This chapter argues for a notion of time that allows time travel. In order to time traveling to happen, in contrast to Presentism, the chapter demonstrates that we can change the past and we have some place where to travel. It shows the advantages of a non-presentist ontology that advocates for indeterminacy of future facts based not on its absence of truth-value, but on the overdetermination of future facts. The conclusion is that to break the causal chain is impossible in (...) we are placed in the same causal line. But if we rethink the time traveling as a trans-world traveling, it is possible to open a new causal line anytime that someone travel in time, to the past as well as to the future. (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)

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.

On a Molinist account of creation and providence, not only is there is a complete set of truths about what every possible person would freely do in any possible set of circumstances, but these conditional truths are part of the very explanation of our existence. Robert Adams has recently argued that the explanatory priority of these conditionals undermines libertarian freedom. In the present essay, I take at close look at Adams’ argument and at the Molinist response of Thomas Flint. After (...) showing that Flint’s response is inadequate, I develop what I believe to be a more successful Molinist response to Adams’ argument. Along the way, I seek to provide some insight into the nature of libertarian freedom and the proper interpretation of the much discussed “principle of alternate possibilities.”. (shrink)

According to many orthodox Christian theologies Jesus is not merely sinless but impeccable: he not only did not sin but could not. This is puzzling because one can only sin by doing something else and, prima face, Jesus can do actions that you or I could do by which we would sin. I suggest that appearances to the contrary, Jesus cannot do a variety of actions that a merely human duplicate could do. His doing sinful actions is compossible with a (...) range of empirical facts about his physical abilities and circumstances of the sort we ordinarily take into account in assessing what a person can do, but not with a wider range of theological facts concerning his divinity. Like Tim, Lewis’s time-traveler, who can kill Grandfather relative to facts about his immediate circumstances and abilities but not relative to a wider range of facts, Jesus ‘can’ in the ordinary sense sin, though he will not, but relative to a wider range of facts which obtain in virtue of his divinity, cannot. (shrink)

In this note, I argue that knowledge of an action’s effect undermines an agent’s reason to act. This undermining occurs in some cases of bringing about the past, but also in some cases of forwards causation. I consider the suggestion that it is not knowledge but truth that undermines reasons to act, giving rise to the spectre of fatalism. Thankfully, this spectre can be banished.

In 1987, Roy Sorensen coined the term “parahistory” to denote the hypothetical study of evidence retrieved via time travel. Parahistory would thus stand to history rather as parapsychology does to psychology; studying data (in this case artefacts) that are obtained in ways unrecognised by orthodox science. This paper considers future-derived parahistorical artefacts. Past/future asymmetries threaten irresolvable problems in calibrating future objects' periods, in dating future artefacts and insulating them from causal loops. In turn, causal loop objects at best cannot be (...) non-arbitrarily dated at all and at worst, cannot even be artefacts. Even if there can be evidence for travel from the future, any such evidence that appeals to future artefacts faces pervasive difficulties and is very unlikely to be compelling. (shrink)