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.

In this paper, I argue that the thesis that time travel is logically possible, is inconsistent with the necessary truth of any of the usual ‘open futureobjective present’ models of the universe. It has been relatively uncontroversial until recently to hold that presentism is inconsistent with the possibility of time travel. I argue that recent arguments to the contrary do not show that presentism is consistent with time travel. Moreover, the necessary truth of other open future-objective present models which we (...) might, prima facie, have supposed to be more amenable to the possibility of time travel, turn out also to be inconsistent with this possibility. (shrink)

The possibility of changing the past by means of time-travel appears to depend on the possibility of distinguishing the past as it is ‘before’ and ‘after’ the time-travel. So far, all the metaphysical models that have been proposed to account for the possibility of past-changing time-travels operate this distinction by conceiving of time as multi-dimensional, and thus by significantly inflating our metaphysics of time. The aim of this article is to argue that there is an intuitive sense in which past-changing (...) time-travels are metaphysically possible also in one-dimensional time. (shrink)

Many defenders of the possibility of time travel into the past also hold that such time travel places no restrictions on what said time travelers can do. Some hold that it places at least a few restrictions on what time travelers can do. In attempting to resolve this dispute, I reached a contrary conclusion. Time travelers to the past cannot do other than what they in fact do. Using a very weak notion of can, I shall argue that the correspondingly (...) strong cannot do otherwise applies in the case of backwards time travel. I defend this result from objections. (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)

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)

What's the point of time travel? Not to change the past; no matter how carefully a time traveler plans, all of her attempts to change the past end in failure. Paul Horwich has argued that the implausibility of such failures gives us reason to doubt that there will be frequent time travel to the local past. I defend a modified version of Horwich's argument and show how we might gain evidence about the chance of there being frequent time travel in (...) the future without having any information that explains why that chance value obtains. (shrink)

This article discusses the possibility of some outlandish tropes from time travel fiction, such as people reversing in age as they time travel or the universe being destroyed because a time traveler kills their ancestor. First, I discuss what type of possibility we might have in mind, detailing ‘close possibility’ as one such candidate. Secondly, I argue that—with only little exception—these more outlandish tropes fail to be closely possible. Thirdly, I discuss whether these outlandish tropes may nevertheless be more broadly (...) possible (e.g., metaphysically or logically possible), arguing that whether they are or not depends upon your favored metaphysics of the laws of nature. (shrink)

In some stories, time travellers cannot change the past. It is widely accepted that this is metaphysically possible. In some stories, time travellers can change the past. Many philosophers have explained how that, too, is metaphysically possible. This paper considers narratives where sometimes the past can change and sometimes it cannot, arguing that this is also something that is possible. Further, I argue that we can make sense of stories where some events appear to be ‘fixed points in time’.

The four principal competing substance ontologies are substratum theory, bundle theory, primitive substance theory, and hylomorphism. Both historically and in the recent literature, most arguments pertaining to these four theories have been developed under the assumption that only one of them can be true. However there is room in this debate for various forms of pluralism: mild pluralism here refers to the view that while only one of these four theories is true of our world, there is at least one (...) other possible world in which a different substance ontology obtains; moderate pluralism refers to the view that while only one of these four theories is true of our world, there is at least one other possible world in which multiple substance ontologies obtain ; and extreme pluralism refers to the view that our own actual world contains substances belonging to different substance ontologies. In this paper I lay out a novel argument for a version of extreme pluralism. (shrink)

Kenneth Silver has recently argued that backwards causation is common in the context of social institutions. I consider this claim in detail and conclude that backwards causation is not the most plausible interpretation of what is going on in the cases Silver considers. Nonetheless, I show that these cases can teach us some interesting lessons about institutional facts. In particular, I argue that in order to avoid contradiction due to conflicting declarations in these cases, we must conclude that the properties (...) involved in institutional facts are relational properties. (shrink)

Tim travels back in time and tries to kill his grandfather before his father was born. Tim fails. But why? Lewis's response was to cite "coincidences": Tim is the unlucky subject of gun jammings, banana peels, sudden changes of heart, and so on. A number of challenges have been raised against Lewis's response. The latest of these focuses on explanation. This paper diagnoses the source of this new disgruntlement and offers an alternative explanation for Tim's failure, one that Lewis would (...) not have liked. The explanation is an obvious one but controversial, so it is defended against all the objections that can be mustered. (shrink)

The standard philosophical view of time travel has it that time travelers cannot change the past. It has been argued by some that the standard view is false, and that this can be shown using a two-dimensional model of time. I defend the standard view against this attack. I show, first, that the addition of a second temporal dimension does not provide a model of changing the past and, second, that neither does the addition of n temporal dimensions for any (...) n > 1. (shrink)

The goal of this paper is to defend the general tenet that time travelers cannot change the past within B-theoretical models of time, independently of how many temporal dimensions there are. Baron Pacific Philosophical Quarterly, 98, 129–147 offered a strong argument intended to reach this general conclusion. However, his argument does not cover a peculiar case, i.e. a B-theoretical one-dimensional model of time that allows for the presence of internal times. Loss Pacific Philosophical Quarterly, 96, 1–11 used the latter model (...) to argue that time travelers can change the past within such model. We show a way to debunk Loss’s argument, so that the general tenet about the impossibility of changing the past within B-theoretical models is maintained. (shrink)

This paper explores mutable futurism, the view according to which the future can literally change—that is, it can happen that a future time t changes from containing an event E to lacking it. Mutable futurism has received little attention so far, and the details and implications of the view are underexplored in the literature. For instance, it currently lacks a precise metaphysical model and a formal semantics. Although we do not endorse mutable futurism, our goal here is to strengthen the (...) case for mutable futurism and help establish it as a worthy contender in the debate on the philosophy of time. To attain this goal, we try to make mutable futurism, along with its metaphysical and inferential commitments, as clear as possible, by providing it with a coherent metaphysical model and a plausible semantics, and we show that it can be backed by theoretical reasons. (shrink)