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 Makes Time Special? by Craig Callender, Oxford University Press, 2017. xx + 344 pp.

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’.

This paper examines various philosophical arguments to do with time travel. It argues that time travel has not been shown to be logically impossible. It then considers whether time travel would give rise to improbable strings of coincidences, or closed causal loops. Finally, it considers whether we could ever be justified in believing someone who claimed to be a time traveller, or whether we would always be more justified in believing that the claimant was either deluded or trying to deceive (...) us. For this last issue the Terry Gilliam film ‘Twelve Monkeys’ is used as an example. (shrink)

In this paper, I argue that there is an inconsistency between two presentist doctrines: that of ontological symmetry and asymmetry of fixity. The former refers to the presentist belief that the past and future are equally unreal. The latter refers to the A-Theoretic intuition that the past is closed or actual, and the future is open or potential. My position in this paper is that the presentist is unable to account for the temporal asymmetry that is so fundamentally a part (...) of her theory. In Section I, I briefly outline a recent defence of presentism due to Craig, and argue that a flaw in this defence highlights the tension between the presentist's doctrines of ontological symmetry and asymmetry of fixity. In Section II, I undertake an investigation, on the presentist's behalf, in order to determine whether she is capable of reconciling these two doctrines. In the course of the investigation, I consider different asymmetries, other than that of ontology, which might be said fundamentally to constitute temporal asymmetry, and the asymmetry of fixity in particular. In Section III, I also consider whether the presentist is able to avail herself of some of the standard B-Theoretic accounts of the asymmetry of fixity, and argue that she cannot. Finally, I conclude that temporal asymmetry cannot be accounted for (or explained) other than through the postulation of an ontological asymmetry. (shrink)

Philosophy of time, as practiced throughout the last hundred years, is both language- and existence-obsessed. It is language-obsessed in the sense that the primary venue for attacking questions about the nature of time—in sharp contrast to the primary venue for questions about space—has been philosophy of language. Although other areas of philosophy have long recognized that there is a yawning gap between language and the world, the message is spreading slowly in philosophy of time.[1] Since twentieth-century analytic philosophy as a (...) whole often drew metaphysical conclusions from arguments with linguistic premises, philosophy of time perhaps may be forgiven for this transgression. Connected to this language-saturated way of doing philosophy, however, is a hitherto unnoticed obsession, equally unhealthy; namely, an obsession with existence. Existence draws the very lines of debate in philosophy of time: “eternalists” believe past, present and future events all ‘equally’ exist, “possibilists” believe that past and present events exist, and “presentists” believe that only present events enjoy this lofty status.[2] These differences between what events exist as of some other time are supposed to explain the main puzzles surrounding time. This fixation on existence, I submit, is a lingering symptom of the language-saturated days of philosophy of time.[3] And just as linguistic issues such as the ineliminability of tense fail to elucidate time and temporal experience, so too do the “existence debates” fail to explain much of what is interesting about time. Philosophers should have more to say about such a fascinating topic. (shrink)

in Ian Jarvie, Karl Milford and David Miller (eds.): Karl Popper: A centenary assessment, Aldershot: Ashgate 2006, Chapter 45, pp. 57–70.

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)

Entropy is ubiquitous in physics, and it plays important roles in numerous other disciplines ranging from logic and statistics to biology and economics. However, a closer look reveals a complicated picture: entropy is defined differently in different contexts, and even within the same domain different notions of entropy are at work. Some of these are defined in terms of probabilities, others are not. The aim of this chapter is to arrive at an understanding of some of the most important notions (...) of entropy and to clarify the relations between them, After setting the stage by introducing the thermodynamic entropy, we discuss notions of entropy in information theory, statistical mechanics, dynamical systems theory and fractal geometry. (shrink)

Thermodynamics is the science that describes much of the time asymmetric behavior found in the world. This entry's first task, consequently, is to show how thermodynamics treats temporally ‘directed’ behavior. It then concentrates on the following two questions. (1) What is the origin of the thermodynamic asymmetry in time? In a world possibly governed by time symmetric laws, how should we understand the time asymmetric laws of thermodynamics? (2) Does the thermodynamic time asymmetry explain the other temporal asymmetries? Does it (...) account, for instance, for the fact that we know more about the past than the future? The discussion thus divides between thermodynamics being an explanandum or explanans. In the former case the answer will be found in philosophy of physics; in the latter case it will be found in metaphysics, epistemology, and other fields, though in each case there will be blurring between the disciplines. (shrink)

It is exceedingly frequent for people to speak of the ‘passing of time’. We do not, on the other hand, speak of the ‘passing of space’. There do not seem to be any common locutions concerning spatial passage analogous to those of time’s assumed passage. Further, there is a long held belief in the philosophy of time that there is no spatial analogue of the passage of time. This opinion does not take into account circumstances that cannot be noticed in (...) day-to-day existence and which indicate that there is such a spatial analogue. (shrink)

I criticize Shimony's argument from the Transient Now (Shimony 1993) that the B-series view of time is inadequate but offer a reading of that argument that is more charitable than one offered and rejected by Eilstein (1996). Shimony's argument turns on putative phenomenological features of the Now (singularity and numerical identity) but transience only arises as a logical implication of those features. Transience is thus a second order phenomenon. If these two features are accurate then the B-series cannot provide a (...) complete account of the Now and Eilstein misses the role of Shimony's Phenomenological Principle (PP) in this regard. Holding a B-theoretic view then demands giving up the numerical identity of person-slices across time. (shrink)

Or better: time asymmetry in thermodynamics. Better still: time asymmetry in thermodynamic phenomena. “Time in thermodynamics” misleadingly suggests that thermodynamics will tell us about the fundamental nature of time. But we don’t think that thermodynamics is a fundamental theory. It is a theory of macroscopic behavior, often called a “phenomenological science.” And to the extent that physics can tell us about the fundamental features of the world, including such things as the nature of time, we generally think that only fundamental (...) physics can. On its own, a science like thermodynamics won’t be able to tell us about time per se. But the theory will have much to say about everyday processes that occur in time; and in particular, the apparent asymmetry of those processes. The pressing question of time in the context of thermodynamics is about the asymmetry of things in time, not the asymmetry of time, to paraphrase Price ( , ). I use the title anyway, to underscore what is, to my mind, the centrality of thermodynamics to any discussion of the nature of time and our experience in it. The two issues—the temporal features of processes in time, and the intrinsic structure of time itself—are related. Indeed, it is in part this relation that makes the question of time asymmetry in thermodynamics so interesting. This, plus the fact that thermodynamics describes a surprisingly wide range of our ordinary experience. We’ll return to this. First, we need to get the question of time asymmetry in thermodynamics out on the table. (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)

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)

The paper tries to demonstrate that the process of the increase of entropy does not explain the asymmetry of time itself because it is unable to account for its fundamental asymmetries, that is, the asymmetry of traces (we have traces of the past and no traces of the future), the asymmetry of causation (we have an impact on future events with no possibility of having an impact on the past), and the asymmetry between the fixed past and the open future, (...) To this end, the approaches of Boltzmann, Reichenbach (and his followers), and Albert are analysed. It is argued that we should look for alternative approaches instead of this, namely we should consider a temporally asymmetrical physical theory or seek a source of the asymmetry of time in metaphysics. This second approach may even turn out to be complementary if only we accept that metaphysics can complement scientific research programmes. (shrink)

Determinism is usually understood as a commonly clear and obvious thesis. In the most of the actual literature a character of determinism is rarely enough explicitly underlined and we believe that it is the reason why common uses of the term often leads to inconsistencies and present a source of misunderstandings of different sorts. Here we will try to show that that there are many forms of determinism; that the concept of determinism has a composite character; and that conceptions of (...) determinism can be mutually discriminated and organized according to particular elements they are consisting of by applying the procedure of classification. (shrink)

The thesis proposes, defends, and applies a new model of inter-theoretic reduction, called "Neo-Nagelian" reduction. There are numerous accounts of inter-theoretic reduction in the philosophy of science literature but the most well-known and widely-discussed is the Nagelian one. In the thesis I identify various kinds of problems which the Nagelian model faces. Whilst some of these can be resolved, pressing ones remain. In lieu of the Nagelian model, other models of inter-theoretic reduction have been proposed, chief amongst which are so-called (...) "New Wave" models. I show these to be no more adequate than the original Nagelian model. I propose a new model of inter-theoretic reduction, Neo-Nagelian reduction. This model is structurally similar to the Nagelian one, but differs in substantive ways. In particular I argue that it avoids the problems pertaining to both the Nagelian and New Wave models. Multiple realizability looms large in discussions about reduction: it is claimed that multiply realizable properties frustrate the reduction of one theory to another in various ways. I consider these arguments and show that they do not undermine the Neo-Nagelian of reduction of one theory to another. Finally, I apply the model to statistical mechanics. Statistical mechanics is taken to be a reductionist enterprise: one of the aims of statistical mechanics is to reduce thermodynamics. Without an adequate model of inter-theoretic reduction one cannot assess whether it succeeds; I use the Neo-Nagelian model to critically discuss whether it does. Specifically, I consider two very recent derivations of the Second Law of thermodynamics, one from Boltzmannian classical statistical mechanics and another from quantum statistical mechanics. I argue that they are partially successful, and that each makes for a promising line of future research. (shrink)

Newton a susținut ideea timpului absolut, spre deosebire de Leibniz pentru care timpul este doar o relație între evenimente și nu poate fi exprimat în mod independent, afirmație în concordanță ci relativitatea spațiu-timpului. Eternismul susține că trecutul și viitorul există într-un sens real, mergându-se până la ideea că timpul este o dimensiune similară cu dimensiunile spațiale, că evenimentele viitoare și trecute sunt "prezente" pe axa timpului, dar această opinie este contestată. Cel mai cunoscut exemplu de imposibilitate a călătoriei în timp (...) este paradoxul bunicului sau argumentul auto-infanticidului: o persoană care călătorește în trecut și își ucide propriul bunic, împiedicând astfel existența unuia din părinți, și deci propria sa existență. DOI: 10.13140/RG.2.2.12629.47843. (shrink)

The article explores the strategy of reconciliation of the idea of objective flow of time with science. In the first part of my paper, I analyze different conceptions of the passage of time and ponder on how we should understand it. The second part is de-voted to the problem whether there is the passage of time in science.

Though there are many analogies between time and space, there appear to be three commonplace yet deeply perplexing features of time that reveal it to be quite unlike space. These can be called ‘orientation’, ‘flow’ and ‘presence’. By orientation I mean that there is a direction to time, a temporal order between events which is not merely a reflection of how they are observed (what McTaggart 1908/1968 labelled the B-series time). Assertions that objects stand in spatial relations, such as to (...) the left of, or above, or to the north of explicitly depend upon the position from which they are asserted or upon arbitrary, conventionally established spatial frameworks. There is nothing intrinsic about them; the objects involved are, so to speak, indifferent to them. Temporal relations are not like that – times are not just arranged along, as it were, a line but are successive along that imaginary line. Whether one event is before or after another is not (altogether) dependent upon how, or from where, they are viewed. Nature appears to respect temporal orientation, as enshrined in the laws of thermodynamics, though it remains a deep mystery exactly how the temporally symmetric basic laws of physics ground strongly asymmetric temporal processes (see Sklar 1993). (shrink)

On propose quelques réflexions sur le concept de temps, tout d'abord rappelant la diversité des expériences et des consciences du temps, et montrant comment le temps des sciences et de la physique est relié à cette expérience et à cette conscience qui en est prise, notamment en ce qui concerne le rapport entre l'instant et la durée. On s'efforce ensuite de tirer deux leçons des développements sur le concept de temps tel qu'il se présente en physique. La première est que (...) le concept de temps est construitpar la pensée, et ne nous est pas directement donné, soit par la nature, soit par notre «sens interne». Cela apparait, notamment, avec l'introduction du temps comme paramètre de la dynamique par Galilée, puis avec la définition du temps «absolu et mathématique » par Newton en vue de constituer le «temps instantané» de la loi fondamentale de la mécanique, et enfin avec la critique des limites de cette conception qui aboutit à la formulation de la relativité du temps et de son lien de constitution à l'espace (construction de l'espace-temps). La seconde leçon est que le temps se définit et se détermine par les phénomènes(et les objets) de la nature (qui se ramènent aux propriétés de la matière), alors qu'on a longtemps cru l'inverse. Cela apparait notamment avec la soumission du temps, dans la reconstruction du concept effectuée par Einstein, d'abord à des principes physiques(avec la relativité restreinte), ensuite avec sa détermination, conjointement à l'espace (dans l'espace-temps), par les champs de gravitation, qui sont des propriétés de la matière. Ce caractère est également confirmé par la deuxième loi de la thermodynamique et par les développements récents de la cosmologie. (shrink)

The most well-known example of the impossibility of traveling in time is the grandfather paradox or self-infanticide argument: a person who travels in the past and kills his own grandfather, thus preventing the existence of one of his parents and thus his own existence. A philosophical response to this paradox would be the impossibility of changing the past, like Novikov self-consistency principle (if an event exists that would cause a paradox or any "change" to the past whatsoever, then the probability (...) of that event is zero, thus it would be impossible to create time paradoxes). DOI: 10.13140/RG.2.2.31279.79521. (shrink)

Celem artykułu jest pokazanie, skąd się biorą nasze trudności z wyjaśnieniem, na czym polega upływ czasu, oraz przedstawienie pewnej propozycji rozwiązania tego problemu, opartej na koncepcji dynamicznego istnienia rzeczy, a rozwijającej ideę absolutnego stawania się. Rozważania oparte są na założeniu, że nasze podstawowe teorie metafizyczne – podobnie jak te stosowane w naukach przyrodniczych – powinny spełniać warunek spójności, prostoty oraz bogatej zawartości.