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)

In a quantum universe with a strong arrow of time, it is standard to postulate that the initial wave function started in a particular macrostate---the special low-entropy macrostate selected by the Past Hypothesis. Moreover, there is an additional postulate about statistical mechanical probabilities according to which the initial wave function is a ''typical'' choice in the macrostate. Together, they support a probabilistic version of the Second Law of Thermodynamics: typical initial wave functions will increase in entropy. Hence, there are (...) two sources of randomness in such a universe: the quantum-mechanical probabilities of the Born rule and the statistical mechanical probabilities of the Statistical Postulate. I propose a new way to understand time's arrow in a quantum universe. It is based on what I call the Thermodynamic Theories of Quantum Mechanics. According to this perspective, there is a natural choice for the initial quantum state of the universe, which is given by not a wave function but by a density matrix. The density matrix plays a microscopic role: it appears in the fundamental dynamical equations of those theories. The density matrix also plays a macroscopic / thermodynamic role: it is exactly the projection operator onto the Past Hypothesis subspace. Thus, given an initial subspace, we obtain a unique choice of the initial density matrix. I call this property "the conditional uniqueness" of the initial quantum state. The conditional uniqueness provides a new and general strategy to eliminate statistical mechanical probabilities in the fundamental physical theories, by which we can reduce the two sources of randomness to only the quantum mechanical one. I also explore the idea of an absolutely unique initial quantum state, in a way that might realize Penrose's idea of a strongly deterministic universe. (shrink)

I advocate Time-Slice Rationality, the thesis that the relationship between two time-slices of the same person is not importantly different, for purposes of rational evaluation, from the relationship between time-slices of distinct persons. The locus of rationality, so to speak, is the time-slice rather than the temporally extended agent. This claim is motivated by consideration of puzzle cases for personal identity over time and by a very moderate form of internalism about rationality. Time-Slice Rationality (...) conflicts with two proposed principles of rationality, Conditionalization and Reflection. Conditionalization is a diachronic norm saying how your current degrees of belief should fit with your old ones, while Reflection is a norm enjoining you to defer to the degrees of belief that you expect to have in the future. But they are independently problematic and should be replaced by improved, time-slice-centric principles. Conditionalization should be replaced by a synchronic norm saying what degrees of belief you ought to have given your current evidence and Reflection should be replaced by a norm which instructs you to defer to the degrees of belief of agents you take to be experts. These replacement principles do all the work that the old principles were supposed to do while avoiding their problems. In this way, Time-Slice Rationality puts the theory of rationality on firmer foundations and yields better norms than alternative, non-time-slice-centric approaches. (shrink)

On one popular view, the general covariance of gravity implies that change is relational in a strong sense, such that all it is for a physical degree of freedom to change is for it to vary with regard to a second physical degree of freedom. At a quantum level, this view of change as relative variation leads to a fundamentally timeless formalism for quantum gravity. Here, we will show how one may avoid this acute ‘problem of time’. Under our (...) view, duration is still regarded as relative, but temporal succession is taken to be absolute. Following our approach, which is presented in more formal terms in, it is possible to conceive of a genuinely dynamical theory of quantum gravity within which time, in a substantive sense, remains. 1 Introduction1.1 The problem of time1.2 Our solution2 Understanding Symmetry2.1 Mechanics and representation2.2 Freedom by degrees2.3 Voluntary redundancy3 Understanding Time3.1 Change and order3.2 Quantization and succession4 Time and Gravitation4.1 The two faces of classical gravity4.2 Retaining succession in quantum gravity5 Discussion5.1 Related arguments5.2 Concluding remarks. (shrink)

Two of the most difficult problems in the foundations of physics are (1) what gives rise to the arrow of time and (2) what the ontology of quantum mechanics is. I propose a unified 'Humean' solution to the two problems. Humeanism allows us to incorporate the Past Hypothesis and the Statistical Postulate into the best system, which we then use to simplify the quantum state of the universe. This enables us to confer the nomological status to the quantum state (...) in a way that adds no significant complexity to the best system and solves the ''supervenient-kind problem'' facing the original version of the Past Hypothesis. We call the resultant theory the Humean unification. It provides a unified explanation of time asymmetry and quantum entanglement. On this theory, what gives rise to time's arrow is also responsible for quantum phenomena. The new theory has a separable mosaic, a best system that is simple and non-vague, less tension between quantum mechanics and special relativity, and a higher degree of theoretical and dynamical unity. The Humean unification leads to new insights that can be useful to Humeans and non-Humeans alike. (shrink)

The epistemology of self-locating belief concerns itself with how rational agents ought to respond to certain kinds of indexical information. I argue that those who endorse the thesis of Time-Slice Rationality ought to endorse a particular view about the epistemology of self-locating belief, according to which ‘essentially indexical’ information is never evidentially relevant to non-indexical matters. I close by offering some independent motivations for endorsing Time-Slice Rationality in the context of the epistemology of self-locating belief.

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)

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)

In "Changing the Past" (2010), Peter van Inwagen argues that a time traveler can change the past without paradox in a growing block universe. After erasing the portion of past existence that generates paradox, a new, non-paradox-generating block can be "grown" after the temporal relocation of the time traveler. -/- I articulate and explore the underlying mechanism of Van Inwagen's model: the time traveler's control over the location of the objective present. Van Inwagen's model is aimed at (...) preventing paradox by changing the past, but it achieves something broader than paradox avoidance: it gives tools for a new model of time travel. I use van Inwagen's tools to develop a new kind of time travel in which in which the location of the objective present is shifted by the time traveler. I call this type of time travel Movable Objective Present, or MOP. After defining MOP, I argue that it is compatible with any theory of time that accepts hypertime, including presentism and moving spotlight theory. (shrink)

This paper argues for the following disjunction: either we do not live in a world with a branching temporal structure, or backwards time travel is nomologically impossible, given the initial state of the universe, or backwards time travel to our space-time location is impossible given large-scale facts about space and time. A fortiori, if backwards time travel to our location is possible, we do not live in a branching universe.

This essay aims to provide a self-contained introduction to time in relativistic cosmology that clarifies both how questions about the nature of time should be posed in this setting and the extent to which they have been or can be answered empirically. The first section below recounts the loss of Newtonian absolute time with the advent of special and general relativity, and the partial recovery of absolute time in the form of cosmic time in some (...) cosmological models. Section II considers the beginning and end of time in a broader class of models in which there is not an analog of Newtonian absolute time. As we will see, reasonable physical assumptions imply that the universe is finite to the past, and Section III turns to consideration of the “beginning” itself. We critically review conventional wisdom that a “singularity” reveals flaws in general relativity and briefly assess ways of avoiding the singularity. (shrink)

It is often thought that there is little that seems more obvious from experience than that time objectively passes, and that time is, in this respect, quite unlike space. Yet nothing in the physical picture of the world seems to correspond to the idea of such an objective passage of time. In this paper, I discuss some attempts to explain this apparent conflict between appearance and reality. I argue that existing attempts to explain the conflict as the (...) result of a perceptual illusion fail, and that it is, in fact, the nature of memory, rather than perception, that explains why we are inclined to think of time as passing. I also offer a diagnosis as to why philosophers have sometimes been tempted to think that an objective passage of time seems to figure directly in perceptual experience, even though it does not. (shrink)

The idea of a moving present or ‘now’ seems to form part of our most basic beliefs about reality. Such a present, however, is not reflected in any of our theories of the physical world. I show in this article that presentism, the doctrine that only what is present exists, is in conflict with modern relativistic cosmology and recent advances in neurosciences. I argue for a tenseless view of time, where what we call ‘the present’ is just an emergent (...) secondary quality arising from the interaction of perceiving self-conscious individuals with their environment. I maintain that there is no flow of time, but just an ordered system of events. (shrink)

This article argues that existing approaches to programming ethical AI fail to resolve a serious moral-semantic trilemma, generating interpretations of ethical requirements that are either too semantically strict, too semantically flexible, or overly unpredictable. This paper then illustrates the trilemma utilizing a recently proposed ‘general ethical dilemma analyzer,’ _GenEth_. Finally, it uses empirical evidence to argue that human beings resolve the semantic trilemma using general cognitive and motivational processes involving ‘mental time-travel,’ whereby we simulate different possible pasts and futures. (...) I demonstrate how mental time-travel psychology leads us to resolve the semantic trilemma through a six-step process of interpersonal negotiation and renegotiation, and then conclude by showing how comparative advantages in processing power would plausibly cause AI to use similar processes to solve the semantic trilemma more reliably than we do, leading AI to make better moral-semantic choices than humans do by our very own lights. (shrink)

This paper suggests that time could have a much richer mathematical structure than that of the real numbers. Clark & Read (1984) argue that a hypertask (uncountably many tasks done in a finite length of time) cannot be performed. Assuming that time takes values in the real numbers, we give a trivial proof of this. If we instead take the surreal numbers as a model of time, then not only are hypertasks possible but so is an (...) ultratask (a sequence which includes one task done for each ordinal number—thus a proper class of them). We argue that the surreal numbers are in some respects a better model of the temporal continuum than the real numbers as defined in mainstream mathematics, and that surreal time and hypertasks are mathematically possible. (shrink)

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)

What would it be for a process to happen backwards in time? Would such a process involve different causal relations? It is common to understand the time-reversal invariance of a physical theory in causal terms, such that whatever can happen forwards in time can also happen backwards in time. This has led many to hold that time-reversal symmetry is incompatible with the asymmetry of cause and effect. This article critiques the causal reading of time (...) reversal. First, I argue that the causal reading requires time-reversal-related models to be understood as representing distinct possible worlds and, on such a reading, causal relations are compatible with time-reversal symmetry. Second, I argue that the former approach does, however, raise serious sceptical problems regarding the causal relations of paradigm causal processes and as a consequence there are overwhelming reasons to prefer a non-causal reading of time reversal, whereby time reversal leaves causal relations invariant. On the non-causal reading, time-reversal symmetry poses no significant conceptual nor epistemological problems for causation. _1_ Introduction _1.1_ The directionality argument _1.2_ Time reversal _2_ What Does Time Reversal Reverse? _2.1_ The B- and C-theory of time _2.2_ Time reversal on the C-theory _2.3_ Answers _3_ Does Time Reversal Reverse Causal Relations? _3.1_ Causation, billiards, and snooker _3.2_ The epistemology of causal direction _3.3_ Answers _4_ Is Time-Reversal Symmetry Compatible with Causation? _4.1_ Incompatibilism _4.2_ Compatibilism _4.3_ Answers _5_ Outlook. (shrink)

I argue that the following theses are both popular among evidentialists but also jointly inconsistent with evidentialism: 1) Time-Slice Mentalism: one’s justificational properties at t are grounded only by one’s mental properties at t; 2) Experience Ultimacy: all ultimate evidence is experiential; and 3) Sleep Justification: we have justified beliefs while we have dreamless, nonexperiential sleep. Although I intend for this paper to be a polemic against evidentialists, it can also be viewed as an opportunity for them to clarify (...) their views. Furthermore, the paper is not only relevant to evidentialists. For example, the arguments of this paper could give Time-Slice Mentalists a reason to deny evidentialism. (shrink)

In English, discourse reference to time involves grammatical tenses interpreted as temporal anaphors. Recently, it has been argued that conditionals involve modal discourse anaphora expressed by a parallel grammatical system of anaphoric modals. Based on evidence from Kalaallisut, this paper argues that temporal and modal anaphora can be just as precise in a language that does not have either grammatical category. Instead, temporal anaphora directly targets eventualities of verbs, without mediating tenses, while modal anaphora involves anaphoric moods and/or attitudinal (...) verbs. (shrink)

Argues that standard interpretations of Merleau-Ponty's criticisms of Sartrean freedom fail and presents an alternative interpretation that argues that the fundamental issue concerns their different theories of time.

It is often assumed that believing that p for a normative reason consists in nothing more than (i) believing that p for a reason and (ii) that reason’s corresponding to a normative reason to believe that p, where (i) and (ii) are independent factors. This is the Composite View. In this paper, we argue against the Composite View on extensional and theoretical grounds. We advocate an alternative that we call the Prime View. On this view, believing for a normative reason (...) is a distinctive achievement that isn’t exhausted by the mere conjunction of (i) and (ii). Its being an achievement entails that (i) and (ii) are not independent when one believes for a normative reason: minimally, (i) must hold because (ii) holds. Apart from its intrinsic interest, our discussion has important upshots for central issues in epistemology, including the analysis of doxastic justification, the epistemology of perception, and the place of competence in epistemology. (shrink)

Time has multiple aspects and is difficult to define as one unique entity, which therefore led to multiple interpretations in physics and philosophy. However, if the perception of time is considered as a composite time concept, it can be decomposed into basic invariable components for the perception of progressive and support-fixed time and into secondary components with possible association to unit-defined time or tense. Progressive time corresponds to Bergson’s definition of duration without boundaries, which (...) cannot be divided for measurements. Time periods are already lying in the past and fixed on different kinds of support. The human memory is the first automatic support, but any other support suitable for time registration can also be considered. The true reproduction of original time from any support requires conditions identical to the initial conditions, if not time reproduction becomes artificially modified as can be seen with a film. Time reproduction can be artificially accelerated, slowed down, extended or diminished, and also inverted from the present to the past, which only depends on the manipulation of the support, to which time is firmly linked. Tense associated to progressive and support fixed time is a psychological property directly dependent on an observer, who judges his present as immediate, his past as finished and his future as uncertain. Events can be secondarily associated to the tenses of an observer. Unit-defined time is essential for physics and normal live and is obtained by comparison of support-fixed time to systems with regular motions, like clocks. The association of time perception to time units can also be broken. Einstein’s time units became relative, in quantum mechanics, some physicist eliminated time units, others maintained them. Nevertheless, even the complete elimination of time units is not identical to timelessness, since the psychological perception of progressive and support-fixed time still remains and cannot be ignored. It is not seizable by physical methods, but experienced by everybody in everyday life. Contemporary physics can only abandon the association of time units or tenses to the basic components in perceived time. (shrink)

According to the No Alternate Possibilities argument, if time passes then the rate at which it passes could be different. Thus, time cannot pass, since if time passes, then necessarily it passes at a rate of 1 second per second. One response to this argument is to posit hypertime, and to argue that at different worlds, time passes at different rates when measured against hypertime. Since many A-theorists think we can make sense of temporal passage without (...) positing hypertime, we pursue a different response. We describe several worlds that do not contain hypertime, but do contain differential passage: worlds where time passes at different rates in different subregions within the same world. Hence we argue that even if we focus just on the set of worlds that do not contain hypertime (whether this is all, or only some of the worlds) we find that not all these worlds are such that time passes at a rate of 1 second per second. Thus the No Alternate Possibilities argument fails even when restricted to just this set of worlds. (shrink)

Several areas of welfare economics seek to evaluate states of affairs as a function of interpersonally comparable individual utilities. The aim is to map each state of affairs onto a vector of individual utilities, and then to produce an ordering of these vectors that can be represented by a mathematical function assigning a real number to each. When this approach is used in intertemporal contexts, a central theoretical question concerns the evaluative weight to be applied to utility coming at different (...) times. This question concerns the rate of pure time preference, which is one key determinant of the social discount rate. This article argues that the standard philosophical account of pure time preference is mistaken, because it ascribes to economists a methodological commitment they need not, and often do not, accept. This in turn undercuts the most common philosophical objection to pure time preference, which traces at least to Rawls’s A Theory of Justice. The article then evaluates three further objections to pure time preference, concluding that it might still be defensible under certain circumstances. The article closes by articulating a final argument that is suggested by the “Social, Economic and Ethical Concepts and Methods” chapter of the most recent Intergovernmental Panel on Climate Change report. If this further argument is sound, it would constitute a decisive objection to pure time preference as it currently figures in much intertemporal welfare economics. (shrink)

Metaphysics is the part of philosophy that asks questions about the nature of reality – about what there is, and what it is like. The metaphysics of time is the part of the philosophy of time that asks questions about the nature of temporal reality. One central such question is that of whether time passes or flows, or whether it has a dynamic aspect.

It is a remarkable fact that all processes occurring in the observable universe are irre- versible, whereas the equations through which the fundamental laws of physics are formu- lated are invariant under time reversal. The emergence of irreversibility from the funda- mental laws has been a topic of consideration by physicists, astronomers and philosophers since Boltzmann's formulation of his famous \H" theorem. In this paper we shall discuss some aspects of this problem and its connection with the dynamics of (...) space-time, within the framework of modern cosmology. We conclude that the existence of cosmological horizons allows a coupling of the global state of the universe with the local events deter- mined through electromagnetic processes. (shrink)

According to a widespread view, Einstein’s definition of time in his special relativity is founded on the positivist verification principle. The present paper challenges this received outlook. It shall be argued that Einstein’s position on the concept of time, to wit, simultaneity, is best understood as a mitigated version of concept empiricism. He contrasts his position to Newton’s absolutist and Kant’s transcendental arguments, and in part sides with Hume’s and Mach’s empiricist arguments. Nevertheless, Einstein worked out a concept (...) empiricism that is considerably more moderate than what we find in the preceding empiricist tradition and early logical positivism. He did not think that the origin of concepts is in observations, but in conventions, and he also maintained a realist ontology of physical events, which he thought is necessary for his theory. Consequently, his philosophy of time in special relativity is not couched in terms of an anti-metaphysical verificationism. (shrink)

In a quantum universe with a strong arrow of time, we postulate a low-entropy boundary condition to account for the temporal asymmetry. In this paper, I show that the Past Hypothesis also contains enough information to simplify the quantum ontology and define a unique initial condition in such a world. First, I introduce Density Matrix Realism, the thesis that the quantum universe is described by a fundamental density matrix that represents something objective. This stands in sharp contrast to Wave (...) Function Realism, the thesis that the quantum universe is described by a wave function that represents something objective. Second, I suggest that the Past Hypothesis is sufficient to determine a unique and simple density matrix. This is achieved by what I call the Initial Projection Hypothesis: the initial density matrix of the universe is the normalized projection onto the special low-dimensional Hilbert space. Third, because the initial quantum state is unique and simple, we have a strong case for the \emph{Nomological Thesis}: the initial quantum state of the universe is on a par with laws of nature. This new package of ideas has several interesting implications, including on the harmony between statistical mechanics and quantum mechanics, the dynamic unity of the universe and the subsystems, and the alleged conflict between Humean supervenience and quantum entanglement. (shrink)

Continuists maintain that, aside from their distinct temporal orientations, episodic memory and future-oriented mental time travel (FMTT) are qualitatively continuous. Discontinuists deny this, arguing that, in addition to their distinct temporal orientations, there are qualitative metaphysical or epistemological differences between episodic memory and FMTT. This chapter defends continuism by responding both to arguments for metaphysical discontinuism, based on alleged discontinuities between episodic memory and FMTT at the causal, intentional, and phenomenological levels, and to arguments for epistemological discontinuism, based on (...) alleged discontinuities with respect to the epistemic openness of the past and future, the directness or indirectness of our knowledge of past and future, and immunity to error through misidentification. The chapter concludes by sketching a positive argument for continuism. (shrink)

This paper proffers an account of why interdisciplinary research on, inter alia, the nature of time can be fruitful even if the disciplines in question have different explanatory pro-jects. We suggest that the special sciences perform a subject setting role for lower-level disciplines such as physics. In essence, they tell us where, amongst a theory of the physical world, we should expect to locate phenomena such as temporality; they tell us what it would take for there to be (...) class='Hi'>time. Physical theory tells us whether there is anything like that in the world and what its hidden nature is. Only working in tandem can physics and the special sciences locate and describe the phenomenon that is time. (shrink)

According to the B-theory, the passage of time is an illusion. The B-theory therefore requires an explanation of this illusion before it can be regarded as fullysatisfactory; yet very few B-theorists have taken up the challenge of trying to provide one. In this paper I take some first steps toward such an explanation by first making a methodological proposal, then a hypothesis about a key element in the phenomenology of temporal passage. The methodological proposal focuses onthe representational content of (...) the element of experience by virtue of which time seems to pass. The hypothesis involves the claim that the experience of changeinvolves the representation of something enduring, rather than perduring, through any change. (shrink)

It has sometimes been suggested that backwards time travel always incurs causal loops. I show that this is mistaken, by describing worlds where backwards time travel occurs and yet no causal loops occur. Arguments that backwards time travel can occur without causal loops have been given before in the literature, but I show that those arguments are unconvincing.

Mathematically, gauge theories are extraordinarily rich --- so rich, in fact, that it can become all too easy to lose track of the connections between results, and become lost in a mass of beautiful theorems and properties: indeterminism, constraints, Noether identities, local and global symmetries, and so on. -/- One purpose of this short article is to provide some sort of a guide through the mathematics, to the conceptual core of what is actually going on. Its focus is on the (...) Lagrangian, variational-problem description of classical mechanics, from which the link between gauge symmetry and the apparent violation of determinism is easy to understand; only towards the end will the Hamiltonian description be considered. -/- The other purpose is to warn against adopting too unified a perspective on gauge theories. It will be argued that the meaning of the gauge freedom in a theory like general relativity is (at least from the Lagrangian viewpoint) significantly different from its meaning in theories like electromagnetism. The Hamiltonian framework blurs this distinction, and orthodox methods of quantization obliterate it; this may, in fact, be genuine progress, but it is dangerous to be guided by mathematics into conflating two conceptually distinct notions without appreciating the physical consequences. (shrink)

The theorist who denies the objective reality of non-relational temporal properties, or ‘A-series’ determinations, must explain our experience of the passage of time. D.H. Mellor, a prominent denier of the objective reality of temporal passage, draws, in part, on Kant in offering a theory according to which the experience of temporal passage is the result of the projection of change in belief. But Mellor has missed some important points Kant has to make about time-awareness. It turns out that (...) Kant's theory of time-awareness also involves projection – but for him, the projection of temporal passage is necessary to any coherent experience at all, and for this reason events in the world cannot be represented except as exhibiting real tensed change. Consequently we cannot intelligibly suppose the world we know to be without the passage of time. This fact would permit a modest transcendental argument the conclusion of which is that we are entitled to describe the world in terms of temporal passage. (shrink)

The issue of time-awareness presents a critical challenge for empiricism: if temporal properties are not directly perceived, how do we become aware of them? A unique empiricist account of time-awareness suggested by Hume's comments on time in the Treatise avoids the problems characteristic of other empiricist accounts. Hume's theory, however, has some counter-intuitive consequences. The failure of empiricists to come up with a defensible theory of time-awareness lends prima facie support to a non-empiricist theory of ideas.

Much debate in contemporary metaphysics of time has centred on whether or not tense is essential to the understanding of a temporal reality. The rival positions in this debate are associated with two very different pictures of the relationship between time and existence. Those who argue for the dispensability of tense see the phenomenon of tense as an epistemological accretion which infects our perception of the world but is in no way essential to a complete description of reality. (...) With respect to existence, things past and future are supposed to be on an equal footing with things present. Thus the Quinean ‘time slice’ ontology, which sees the world as a four-dimensional entity in space-time, repudiates any ontological significance to the differences between past, present and future. For the Quinean, what differences we see between past, present and future existents pertain to our limited mode of access to reality. In a perception which grasped the world as it really is tense differences would have no place. In this respect the Quinean position resembles Spinoza's claim in the Ethics that in so far as the mind conceives a thing under the dictates of reason it is affected equally, whether the idea be of a thing future, past or present. (shrink)

The thesis revolves around the following questions. What is time? Is time tensed or tenseless? Do things endure or perdure, i.e. do things persist by being wholly present at many times, or do they persist by having temporal parts? Do causes bring their effects into existence, or are they only correlated with each other? Within a realist approach to metaphysics, the author claims that the tensed view of time, the endurance view of persistence, and the production view (...) of causality naturally combine into what is called the dynamic view of temporal reality, and that the tenseless view of time, the perdurance view of persistence, and the correlation view of causality naturally combine into what is called the static view of temporal reality. The author argues in favour of a dynamic view. During the discussion a number of metaphysical problems are addressed. First, it is argued that the charges that the dynamic view is contradictory, made by J.M.E. McTaggart and David Lewis, are viciously circular. Secondly, it is argued that the static view cannot account for change, and deprives metaphysics of essential means to provide natural explanations to empirical phenomena. Thirdly, the author presents a novel account of the nature of necessary causal production. He suggests that the traditional conception of causes as essentially being external to the effects should be abandoned, and that causal production instead should be explicated in terms of reciprocal interactions between coexistent substances. (shrink)

This paper proposes a view of time that takes passage to be the most basic temporal notion, instead of the usual A-theoretic and B-theoretic notions, and explores how we should think of a world that exhibits such a genuine temporal passage. It will be argued that an objective passage of time can only be made sense of from an atemporal point of view and only when it is able to constitute a genuine change of objects across time. (...) This requires that passage can flip one fact into a contrary fact, even though neither side of the temporal passage is privileged over the other. We can make sense of this if the world is inherently perspectival. Such an inherently perspectival world is characterized by fragmentalism, a view that has been introduced by Fine in his ‘Tense and Reality’ (2005). Unlike Fine's tense-theoretic fragmentalism though, the proposed view will be a fragmentalist view based in a primitive notion of passage. (shrink)

There seems to be a "what it is like" to the experience of the flow of time in any conscious activity of ours. In this paper, I argue that the feeling that time passes should be understood as a phenomenal modifier of our mental life, in roughly the same way as the blurred or vivid nature of a visual experience can be seen as an element of the experience that modifies the way it feels, without representing the world (...) as being in a certain way. I defend my positions against the deflationary view according to which the passing of time does not have a specific phenomenal character, and the representationalist view according to which the feeling of time passing is a feature of the representational content of our experience, like being red or yellow. (shrink)

I present a new problem for the tense realist concerning the evaluation of cross-temporal claims, such as ‘John is now taller than Michael was in 1984’. Time can play two different roles in the evaluation of an utterance of a sentence: either as an element that completes the content expressed by the utterance (the completion role), or as part of the circumstances against which the content is evaluated (the evaluation role). It is this latter role that time plays (...) in the realist view of tenses. I argue that if the content of a cross-temporal sentence is taken at face value (as an ascription of a crosstemporally instantiated relation), time does not play the evaluation role. Therefore, the world of the tense realist seems to leave no room for cross-temporality. (shrink)

We develop a theory about the metaphysics of time and modality that combines the conceptual resources devised in recent sympathetic work on ontological pluralism (the thesis that there are fundamentally distinct kinds of being) with the thought that what is past, future, and merely possible is less real than what is present and actual (albeit real enough to serve as truthmakers for statements about the past, future, and merely possible). However, we also show that despite being a coherent, distinctive, (...) and prima facie appealing position, the theory succumbs to what we call the “problem of mixed ontological status”. We conclude that the proponents of the theory can only evade these problems by developing ontological pluralism in a radically different way than it has been by its recent sympathizers. (shrink)

This paper explores the relation of the theory of time and the theory of truth in Deleuze’s philosophy. According to Deleuze, a mutation in our conception of time occurred with Kant. In antiquity, time had been subordinated to movement, it was the measure or the “number of movement” (Aristotle). In Kant, this relation is inverted: time is no longer subordinated to movement but assumes an independence and autonomy of its own for the first time. In (...) Deleuze’s phrasing, time becomes the pure and empty form of everything that moves and changes — not an eternal form (as in Plato), but precisely the form of what is not eternal. In turn, the theory of time is inextricably linked to the concept of truth, since to say that a proposition is true means that it is true “in all times and in all places.” Truth, in other words, is timeless, eternal, non-temporal. When the form of the true is confronted with the form of time, the concept of truth is necessarily put into crisis, and Deleuze’s argument is that time allows the power of the false to assume an autonomy of its own. The analysis will attempt to show how the liberation of time from movement (the pure and empty form of time) leads to a liberation of the false from the true (the power of the false). (shrink)

This is a comprehensive book on the philosophy of time. Leading philosophers discuss the metaphysics of time, our experience and representation of time, the role of time in ethics and action, and philosophical issues in the sciences of time, especially quantum mechanics and relativity theory.

Sceptics about substantial disputes in ontology often argue that when two philosophers seem to disagree on a quantified claim, they are actually equivocating on the notion of existence that they are using. When temporal elements play a central role, as in the debate between presentists and eternalists, the hypothesis of an equivocation with respect to existence acquires more plausibility. However, the anti-sceptic can still argue that this hypothesis is unjustified.

I argue that truth is relative (in the sense recently defended by some prominent analytical philosophers) by focusing on some semantic issues raised by Einstein's theory of relativity together with our ordinary attributions of truth.

Both Martin Heidegger and Harry Frankfurt have argued that the fundamental feature of human identity is care. Both contend that caring is bound up with the fact that we are finite beings related to our own impending death, and both argue that caring has a distinctive, circular and non-instantaneous, temporal structure. In this paper, I explore the way Heidegger and Frankfurt each understand the relations among care, death, and time, and I argue for the superiority of Heideggerian version of (...) this nest of claims. Frankfurt claims that we should conceive of the most basic commitments which practically orient a person in the world and define his identity (“volitional necessities”) as naturalistic facts, foundational for and located completely without the normative space of reasons. In support of this he appeals to the supposedly foundational role played in human life by the instinct for self-preservation, what Frankfurt calls the “love of living.” The claim is that in questions of practical identity there is a definite priority of the factual over the normative. Frankfurt’s naturalistic model of volitional necessity is motivated by a misunderstanding of the temporal structure of care, a misunderstanding that helps lead him to an implausible conception of the basic structures of human identity. Heidegger advances an anti-naturalistic conception of caring, one bound up with his way of understanding how human beings relate to their own future. I argue that the existential, temporal, and normative significance that Frankfurt attributes to the naturalized “love of living” is better captured by the Heideggerian claim that human identity is defined by being “for-the-sake-of” certain projects and commitments, a way of being lived out in the way Heidegger calls “being-towards-death.”. (shrink)

The Whorfian hypothesis has received support from recent findings in psychology, linguistics, and anthropology. This evidence has been interpreted as supporting the view that language modulates all stages of perception and cognition, in accordance with Whorf’s original proposal. In light of a much broader body of evidence on time perception, I propose to evaluate these findings with respect to their scope. When assessed collectively, the entire body of evidence on time perception shows that the Whorfian hypothesis has a (...) limited scope and that it does not affect early stages of time perception. In particular, all the available evidence shows that the scope of language modulation is limited in the case of time perception, and that the most important mechanisms for time perception are cognitive clocks and simultaneity windows, which we use to perceive the temporal properties of events. Language modulation has distorting effects, but only at later stages of processing or with respect to specific categorization tasks. The paper explains what is the role of these effects in the context of all the available evidence on time cognition and perception. (shrink)