This paper is an enquiry into the logical, metaphysical, and physical possibility of time travel understood in the sense of the existence of closed worldlines that can be traced out by physical objects. We argue that none of the purported paradoxes rule out time travel either on grounds of logic or metaphysics. More relevantly, modern spacetime theories such as general relativity seem to permit models that feature closed worldlines. We discuss, in the context of Gödel's infamous argument for the ideality (...) of time based on his eponymous spacetime, what this apparent physical possibility of time travel means. Furthermore, we review the recent literature on so-called time machines, i.e., of devices that produce closed worldlines where none would have existed otherwise. Finally, we investigate what the implications of the quantum behaviour of matter for the possibility of time travel might be and explicate in what sense time travel might be possible according to leading contenders for full quantum theories of gravity such as string theory and loop quantum gravity. (shrink)

There is an old and powerful argument for the claim that divine foreknowledge is incompatible with the freedom to do otherwise. A recent response to this argument, sometimes called the “dependence response,” centers around the claim that God’s relevant past beliefs depend on the relevant agent’s current or future behavior in a certain way. This paper offers a new argument for the dependence response, one that revolves around different cases of time travel. Somewhat serendipitously, the argument also paves the way (...) for a new reply to a compelling objection to the dependence response, the challenge from prepunishment. But perhaps not so serendipitously, the argument also renders the dependence response incompatible with certain views of providence. (shrink)

This article argues that the causal loops that occur in some time-travel scenarios and in certain solutions of the theory of relativity are no more mysterious than the infinitely descending causal chains familiar from Newtonian mechanics.

There is an extensive literature on time travel in both philosophy and physics. Part of the great interest of the topic stems from the fact that reasons have been given both for thinking that time travel is physically possible—and for thinking that it is logically impossible! This entry deals primarily with philosophical issues; issues related to the physics of time travel are covered in the separate entries on time travel and modern physics and time machines. We begin with the definitional (...) question: what is time travel? We then turn to the major objection to the possibility of backwards time travel: the Grandfather paradox. Next, issues concerning causation are discussed—and then, issues in the metaphysics of time and change. We end with a discussion of the question why, if backwards time travel will ever occur, we have not been visited by time travellers from the future. (shrink)

În această lucrare analizez posibilitatea călătoriei în timp pe baza mai multor lucrări de specialitate, printre care cele ale lui Nicholas J.J. Smith ("Time Travel", The Stanford Encyclopedia of Philosophy”), William Grey (”Troubles with Time Travel”), Ulrich Meyer (”Explaining causal loops”), Simon Keller și Michael Nelson (”Presentists should believe in time-travel”), Frank Arntzenius și Tim Maudlin ("Time Travel and Modern Physics") și David Lewis (“The Paradoxes of Time Travel”). Lucrarea începe cu o Introducere în care fac o scurtă prezentare a (...) călătoriei în timp, și continuă cu o Istoria conceptului de călătorie în timp, prezentarea principalelor Aspecte fizice ale călătoriei în timp, inclusiv călătoria în timp în trecut în relativitatea generală și în fizica cuantică și călătoria în timp în viitor, apoi o prezentare a Paradoxul bunicului care este abordat în aproape toate lucrările de specialitate, urmat de o secțiune dedicată Filosofiei călătoriei în timp, și o secțiune în care analizez Buclele cauzale pentru călătoria în timp. Finalizez lucrarea cu Concluzii, în care expun opiniile personale privind călătoria în timp, și Bibliografia pe care se bazează lucrarea. (shrink)

This paper focuses on problems for time travel that specifically concern continuous time-travel to the past, problems to do with potential collisions with past obstacles such as former time-slices of the time traveler herself. These problems have not been discussed nearly as much as other questions about time travel, such as the Grandfather Paradox. Here I focus on discussions by Bernstein, Dowe, Grey and Le Poidevin. After examination, I conclude that only the problems of turning around in time have any (...) merit and present a new proposal of my own for turning around in time without collisions. I assume a Lewisian framework throughout. (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 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)

About the possibility of time traveling based on several specialized works, including those of Nicholas J. J. Smith ("Time Travel"), William Grey (”Troubles with Time Travel”), Ulrich Meyer (”Explaining causal loops”), Simon Keller and Michael Nelson (”Presentists should believe in time-travel”), Frank Arntzenius and Tim Maudlin ("Time Travel and Modern Physics"), and David Lewis (“The Paradoxes of Time Travel”). The article begins with an Introduction in which I make a short presentation of the time travel, and continues with a History (...) of the concept of time travel, main physical aspects of time travel, including backward time travel in the past in general relativity and quantum physics, and time travel in the future, then a presentation of the Grandfather paradox that is approached in almost all specialized works, followed by a section dedicated to the Philosophy of time travel, and a section in which I analyze Causal loops for time travel. I finish my work with Conclusions, in which I sustain my personal opinions on the time travel, and the Bibliography on which the work is based. -/- ISSN 978-606-033-195-7, DOI: 10.58679/TW82554. (shrink)

Extending work of Wittgenstein, Lakoff and Johnson I suggest that it is the metaphors we rely on in order to conceptualise time that provide an illusory space for time-travel-talk. For example, in the “Moving Time” spatialisation of time, “objects” move past the agent from the future to the past. The objects all move in the same direction – this is mapped to time always moving in the same direction. But then it is easy to imagine suspending this rule, and asking (...) why the objects should not start moving in the opposite direction. This is one way of generating the idea of time-travel “back” into the past. Time-travel-talk essentially involves the unaware projection of fragments of our time-talk – taken from powerful conceptual metaphors – onto the nature of reality itself. Understanding this dissolves away the charm and attractions of such talk. (shrink)

There is, among some scientists and philosophers, the idea that any theory that would allow the time travel would introduce causal issues. These types of temporal paradoxes can be avoided by the Novikov self-consistency principle or by a variation in the interpretation of many worlds with interacting worlds. The world in which we live has, according to David Lewis, a Parmenidean ontology: "a manifold of events in four dimensions," and the occupants of the world are the 4-dimensional aggregates of the (...) stages - "temporal lines". The causal loops in backwards time travel involve events that appear to "come from nowhere," paradoxical "self-existent" objects or information, resulting in a bootstrap paradox. Many believe that causality loops are not impossible or unacceptable, but only inexplicable. DOI: 10.13140/RG.2.2.28792.70407. (shrink)

À propos de la possibilité de voyager dans le temps sur la base de plusieurs ouvrages spécialisés, notamment ceux de Nicholas J. J. Smith (« Time Travel »), William Grey (« Troubles with Time Travel »), Ulrich Meyer (« Explaining causal loops »), Simon Keller and Michael Nelson (« Presentists should believe in time-travel »), Frank Arntzenius and Tim Maudlin (« Time Travel and Modern Physics »), et David Lewis (« The Paradoxes of Time Travel »). L'article commence par une (...) Introduction dans laquelle je fais une brève présentation du voyage dans le temps et poursuit par une Histoire du concept de voyage dans le temps, les principaux aspects physiques du voyage dans le temps, y compris les voyages dans le temps dans le passé dans la relativité générale et la physique quantique , et les voyages dans le temps dans le futur, puis une présentation du Paradoxe du grand-père abordé dans presque toutes les œuvres spécialisées, suivie d’une section consacrée à la Philosophie du voyage dans le temps et d’une section dans laquelle j’analyse les Boucles causales pour le voyage dans le temps. Je termine mon travail avec Conclusions, dans laquelle je maintiens mes opinions personnelles sur le voyage dans le temps et la Bibliographie sur laquelle repose le travail. -/- TABLE: -/- Abstract Introducere Istoria conceptului de călătorie în timp Paradoxul bunicului Filosofía călătoriei în timp Buclele cauzale Concluzii Note Bibliografie -/- DOI: 10.13140/RG.2.2.27116.51841. (shrink)

Orice teorie care ar permite călătoria în timp ar introduce probleme de cauzalitate. Aceste tipuri de paradoxuri temporale pot fi evitate prin principiul de consecvență Novikov sau printr-o variație a interpretării multor lumi cu lumi care interacționează. Argumentul clasic împotriva cauzalității înapoi este argumentul bilking, Dacă un eveniment A provoacă un eveniment anterior B, bilking recomandă o încercare de a decorela A și B, adică de a aduce A în cazurile în care B nu a avut loc și de a (...) preveni A în cazurile în care a avut loc B. DOI: 10.13140/RG.2.2.13245.41448. (shrink)

The philosophy of time travel is a sub-field of metaphysics – the study of what there is and what things are like – that considers questions about the possibility of time travel and what a world in which time travel is possible looks like. These questions range from whether time travel is actually possible, to how time travellers can act in the past or future. This thesis delves into a particularly interesting, yet historically undertreated theme: the abilities of time travellers (...) and relatedly their freedom as well. The abilities and freedom of time travellers has been the source of a lot of recent discussion with some polarising views. The minority (which includes Lewis (1976), but also Ted Sider (2002)) argue for the affirmative – that time travellers are free and have the same (or perhaps more) abilities as non-time travellers. The majority (which includes Kadri Vihvelin (1996), Michael Rea (2005), Stephanie Rennick (2015), Alison Fernandes (2020), amongst others) argue for the negative, that time travellers do not have exactly the same freedoms and abilities as non-time travellers. I think that it is a mistake to be so pessimistic about the abilities and freedom of time travellers. I treat concerns about the freedom of time travellers and concerns about the abilities of time travellers as two sides of the same coin. Therefore, in what follows, I argue for two related conclusions. First, I argue that time travellers have all sorts of abilities. Second, I argue that time travellers are just as free as non-time travellers. In arguing for these conclusions, I first produce a novel analysis of ability which reveals important details about how abilities track inputs rather than outputs. Second, I use this new analysis of ability to present a new compatibilist account of free will. If I am right in arguing positively for the abilities and freedoms of time travellers, then this has large implications for both the current time travel discourse and the general debate surrounding freedom. Significantly, I am arguing against some prominent views about time travel and in suggesting that these views are mistaken, I am presenting new ideas about ability and freedom: specifically, that time travellers have the ability and are free to do impossible things. (shrink)