This book is an attempt to get to the bottom of an acute and perennial tension between our best scientific pictures of the fundamental physical structure of the world and our everyday empirical experience of it. The trouble is about the direction of time. The situation (very briefly) is that it is a consequence of almost every one of those fundamental scientific pictures--and that it is at the same time radically at odds with our common sense--that whatever can happen can (...) just as naturally happen backwards. Albert provides an unprecedentedly clear, lively, and systematic new account--in the context of a Newtonian-Mechanical picture of the world--of the ultimate origins of the statistical regularities we see around us, of the temporal irreversibility of the Second Law of Thermodynamics, of the asymmetries in our epistemic access to the past and the future, and of our conviction that by acting now we can affect the future but not the past. Then, in the final section of the book, he generalizes the Newtonian picture to the quantum-mechanical case and (most interestingly) suggests a very deep potential connection between the problem of the direction of time and the quantum-mechanical measurement problem. The book aims to be both an original contribution to the present scientific and philosophical understanding of these matters at the most advanced level, and something in the nature of an elementary textbook on the subject accessible to interested high-school students. Table of Contents: Preface 1. Time-Reversal Invariance 2. Thermodynamics 3. Statistical Mechanics 4. The Reversibility Objections and the Past-Hypothesis 5. The Scope of Thermodynamics 6. The Asymmetries of Knowledge and Intervention 7. Quantum Mechanics Appendix: Gedankenexperiments with Heat Engines Index Reviews of this book: The foundations of statistical mechanisms are often presented in physics textbooks in a rather obscure and confused way. By challenging common ways of thinking about this subject, Time and Chance can do quite a lot to improve this situation. --Jean Bricmont, Science Albert is perfecting a style of foundational analysis that is uniquely his own...It has a surgical precision...and it is ruthless with pretensions. The foundations of thermodynamics is a topic that has accumulated a good deal of dead wood; this is a fire that will burn and burn. --Simon W. Saunders, Oxford University As usual with Albert's work, the exposition is brisk and to the point, and exceptionally clear...The book will be an extremely valuable contribution to the literature on the subject of philosophical issues in thermodynamics and statistical mechanics, a literature which has been thin on the ground but is now growing as it deserves to. --Lawrence Sklar, University of Michigan. (shrink)

Philosophers of physics have long debated whether the Past State of low entropy of our universe calls for explanation. What is meant by “calls for explanation”? In this article we analyze this notion, distinguishing between several possible meanings that may be attached to it. Taking the debate around the Past State as a case study, we show how our analysis of what “calling for explanation” might mean can contribute to clarifying the debate and perhaps to settling it, thus demonstrating the (...) fruitfulness of this analysis. Applying our analysis, we show that two main opponents in this debate, Huw Price and Craig Callender, are, for the most part, talking past each other rather than disagreeing, as they employ different notions of “calling for explanation”. We then proceed to show how answering the different questions that arise out of the different meanings of “calling for explanation” can result in clarifying the problems at hand and thus, hopefully, to solving them. (shrink)

1. Of what use is the concept of causation? Bertrand Russell [1912-13] argued that it is not useful: it is “a relic of a bygone age, surviving, like the monarchy, only because it is erroneously supposed to do no harm.” His argument for this was that the kind of physical theories that we have come to regard as fundamental leave no place for the notion of causation: not only does the word ‘cause’ not appear in the advanced sciences, but the (...) laws that these sciences state are incompatible with causation as we normally understand it. But Nancy Cartwright has argued [1979] that abandoning the concept of causation would cripple science; her conclusion was based not on fundamental physics, but on more ordinary science such as the search for the causes of cancer. She argues that Russell was right that the fundamental theories of modern physics say nothing, even implicitly, about causation, and concludes on this basis that such theories are incomplete. It is with this cluster of issues that I will begin my discussion. (shrink)

Elsewhere I have suggested that the B-theory includes a notion of passage, by virtue of including succession. Here, I provide further support for that claim by showing that uncontroversial elements of the B-theory straightforwardly ground a veridical sense of passage. First, I argue that the B-theory predicts that subjects of experience have a sense of passivity with respect to time that they do not have with respect to space, which they are right to have, even according to the B-theory. I (...) then ask what else might be involved in our experience of time as passing that is not yet vindicated by the B-theoretic conception. I examine a recent B-theoretic explanation of our ‘illusory’ sense of passage, by Robin Le Poidevin, and argue that it explains away too much: our perception of succession poses no more of a problem on the B-theory than it does on other theories of time. Finally, I respond to an objection by Oreste Fiocco that a causal account of our sense of passage cannot succeed, because it leaves out the ‘phenomenological novelty’ of each moment. (shrink)

In his recent article On Relativity Theory and Openness of the Future (1991), Howard Stein proves not only that one can define an objective becoming relation in Minkowski spacetime, but that there is only one possible definition available if one accepts certain natural assumptions about what it is for becoming to occur and for it to be objective. Stein uses the definition supplied by his proof to refute an argument due to Rietdijk (1966, 1976), Putnam (1967) and Maxwell (1985, 1988) (...) that Minkowski spacetime leaves no room for objective becoming whatsoever. However, Stein's proof does not seem to go far enough. By considering only what events have become from the standpoint of any given event, Stein's uniqueness proof fails from the outset to allow for a more general kind of becoming whereby it is understood to occur from the standpoint of events on the particular worldlines followed by observers. This suggests that there may, after all, be more than one way to define objective becoming in Minkowski spacetime once each observer's worldline is allowed to figure in the definition. This suspicion is further aroused by two recent proposals for objective, worldline-dependent becoming due to Peacock (1992) and Muller (1992) who advocate ways of defining becoming that are not equivalent to the definition Stein's uniqueness proof delivers. Nevertheless, we show that Stein's uniqueness proofcan be extended in a natural way to cover this more general kind of becoming, provided one does not enrich standard Minkowski spacetime by privileging certain sets of worldlines over others in an unwarranted manner. Thus we aim to reinforce Stein's point that standard Minkowski spacetime does make room for objective becoming, but in essentially only one way, despite arguments and proposals to the contrary. (shrink)

John Carroll undertakes a careful philosophical examination of laws of nature, causation, and other related topics. He argues that laws of nature are not susceptible to the sort of philosophical treatment preferred by empiricists. Indeed he shows that emperically pure matters of fact need not even determine what the laws are. Similar, even stronger, conclusions are drawn about causation. Replacing the traditional view of laws and causation requiring some kind of foundational legitimacy, the author argues that these phenomena are inextricably (...) intertwined with everything else. This distinctively clear and detailed discussion of what it is to be a law will be valuable to a broad swathe of philosophers in metaphysics, the philosophy of mind, and the philosophy of science. (shrink)

In a classical mechanical world, the fundamental laws of nature are reversible. The laws of nature treat the past and future as mirror images of each other. Temporally asymmetric phenomena are ultimately said to arise from initial conditions. But are the laws of nature also reversible in a quantum world? This paper argues that they are not, that time in a quantum world prefers a particular 'hand' or ordering. I argue, first, that the probabilistic algorithm used in the theory picks (...) out a preferred direction of time for almost all interpretations of the theory, and second, that contrary to the received wisdom the Schr?dinger evolution is also irreversible. The status of Wigner reversal invariance is then discussed. I conclude that the quantum world is fundamentally irreversible, but manages to appear (thanks to Wigner reversal invariance) reversible at the classical level. (shrink)

In a classical mechanical world, the fundamental laws of nature are reversible. The laws of nature treat the past and future as mirror images of each other. Temporally asymmetric phenomena are ultimately said to arise from initial conditions. But are the laws of nature also reversible in a quantum world? This paper argues that they are not, that time in a quantum world prefers a particular 'hand' or ordering. I argue, first, that the probabilistic algorithm used in the theory picks (...) out a preferred direction of time for almost all interpretations of the theory, and second, that contrary to the received wisdom the Schr?dinger evolution is also irreversible. The status of Wigner reversal invariance is then discussed. I conclude that the quantum world is fundamentally irreversible, but manages to appear reversible at the classical level. (shrink)

For the generalizations of thermodynamics to obtain, it appears that a very ‘special’ initial condition of the universe is required. Is this initial condition itself in need of explanation? I argue that it is not. In so doing, I offer a framework in which to think about ‘special’ initial conditions in all areas of science, though I concentrate on the case of thermodynamics. I urge the view that it is not always a serious mark against a theory that it must (...) posit an ‘improbable’ initial condition. (shrink)

This paper considers the possibility that nonrelativistic quantum mechanics tells us that Nature cares about time reversal. In a classical world we have a fundamentally reversible world that appears irreversible at higher levels, e.g., the thermodynamic level. But in a quantum world we see, if I am correct, a fundamentally irreversible world that appears reversible at higher levels, e.g., the level of classical mechanics. I consider two related symmetries, time reversal invariance and what I call ‘Wigner reversal invariance.’ Violation of (...) the first is interesting, for not only would it fly in the face of the usual story about temporal symmetry, but it also appears to imply (as I’ll explain) that time is ‘handed’, or as some have misleadingly said in the literature, ‘anisotropic’. Violation of the second is, as I hope to show, even more interesting. The paper also contains a discussion of two mostly neglected topics: what it means to say time is handed and what warrants such an attribution to time. (shrink)

More than a century ago, Russell launched a forceful attack on causation, arguing not only that modern physics has no need for causal notions but also that our belief in causation is a relic of a pre-scientific view of the world. He thereby initiated a debate about the relations between physics and causation that remains very much alive today. While virtually everybody nowadays rejects Russell's causal eliminativism, many philosophers have been convinced by Russell that the fundamental physical structure of our (...) world doesn't contain causal relations. This raises the question of how to reconcile the central role of causal concepts in the special sciences and in common sense with the putative absence of causation in fundamental physics. (shrink)

Author Max Black argues that language should conform to the discovered regularities of experience it is radically mistaken to assume that the conception of language is a mirror of reality.

Author Max Black argues that language should conform to the discovered regularities of experience it is radically mistaken to assume that the conception of language is a mirror of reality.

Richard Feynman has claimed that anti-particles are nothing but particles `propagating backwards in time'; that time reversing a particle state always turns it into the corresponding anti-particle state. According to standard quantum field theory textbooks this is not so: time reversal does not turn particles into anti-particles. Feynman's view is interesting because, in particular, it suggests a nonstandard, and possibly illuminating, interpretation of the CPT theorem. In this paper, we explore a classical analog of Feynman's view, in the context of (...) the recent debate between David Albert and David Malament over time reversal in classical electromagnetism. (shrink)

A theory is usually said to be time reversible if whenever a sequence of states S 1 , S 2 , S 3 is possible according to that theory, then the reverse sequence of time reversed states S 3 T , S 2 T , S 1 T is also possible according to that theory; i.e., one normally not only inverts the sequence of states, but also operates on the states with a time reversal operator T . David Albert and (...) Paul Horwich have suggested that one should not allow such time reversal operations T on states. I will argue that time reversal operations on fundamental states should be allowed. I will furthermore argue that the form that time reversal operations take is determined by the type of fundamental geometric quantities that occur in nature and that we have good reason to believe that the fundamental geometric quantities that occur in nature correspond to irreducible representations of the Lorentz transformations. Finally, I will argue that we have good reason to believe that space-time has a temporal orientation. (shrink)

A theory is usually said to be time reversible if whenever a sequence of states S 1, S 2, S 3 is possible according to that theory, then the reverse sequence of time reversed states S 3 T, S 2 T, S 1 T is also possible according to that theory; i.e., one normally not only inverts the sequence of states, but also operates on the states with a time reversal operator T. David Albert and Paul Horwich have suggested that (...) one should not allow such time reversal operations T on states. I will argue that time reversal operations on fundamental states should be allowed. I will furthermore argue that the form that time reversal operations take is determined by the type of fundamental geometric quantities that occur in nature and that we have good reason to believe that the fundamental geometric quantities that occur in nature correspond to irreducible representations of the Lorentz transformations. Finally, I will argue that we have good reason to believe that space-time has a temporal orientation. (shrink)

The general claims of this paper are as follows. As a result of chaotic dynamics we can usually not know what the deterministic causes of events are. There will, however, be invariant forwards transition chances from earlier types of events, which we typically call the causes, to later types of events, which we typically call the effects. There will be no invariant backwards transition chances between these types of events. This asymmetry has the same origin and explanation as the arrow (...) of time of thermodynamics. (shrink)

The frequencies with which photons pass through half-silvered mirrors in the forward direction of time is always approximately 1/2, whereas the frequencies with which photons pass through mirrors in the backward direction in time can be highly time-dependent. I argue that whether one should infer from this time-asymmetric phenomenon that time has an objective direction will depend on one's interpretation of quantum mechanics.

Many phenomena in the world display a striking time-asymmetry: the forwards transition frequencies are approximately invariant while the backwards ones are not. I argue in this paper that theories of such phenomena will entail that time has a direction, and that quantum mechanics in particular entails that the future is objectively different from the past.

It is argued that certain recent advances in the construction of a theory of the collapses of Quantum Mechanical wave functions suggest the possibility of new and improved foundations for statistical mechanics, foundations in which epistemic considerations play no role.

This book is an attempt to get to the bottom of an acute and perennial tension between our best scientific pictures of the fundamental physical structure of the ...

Concepts employed in folk descriptions of the world often turn out to be more perspectival than they seem at first sight, involving previously unrecognised sensitivity to the viewpoint or 'situation' of the user of the concept in question. Often, it is progress in science that reveals such perspectivity, and the deciding factor is that we realise that other creatures would apply the same concepts with different extension, in virtue of differences between their circumstances and ours. In this paper I argue (...) that causal concepts are perspectival in this way, and describe the 'situation' on which they depend in terms of an abstract characterisation of the viewpoint of a deliberating agent. I argue that this approach makes better sense than rivals of the apparent asymmetry and temporal orientation of the causal relation. (shrink)

Why is the future so different from the past? Why does the past affect the future and not the other way round? The universe began with the Big Bang - will it end with a `Big Crunch'? Now in paperback, this book presents an innovative and controversial view of time and contemporary physics. Price urges physicists, philosophers, and anyone who has ever pondered the paradoxes of time to look at the world from a fresh perspective, and throws fascinating new light (...) on some of the great mysteries of the universe. (shrink)

A modest proposal concerning laws, counterfactuals, and explanations - - Why be Humean? -- Suggestions from physics for deep metaphysics -- On the passing of time -- Causation, counterfactuals, and the third factor -- The whole ball of wax -- Epilogue : a remark on the method of metaphysics.

As we navigate through life, we model time as flowing, the present as special, and the past as “dead.” This model of time—manifest time—develops in childhood and later thoroughly infiltrates our language, thought, and behavior. It is part of what makes a human life recognizably human. Yet if physics is correct, this model of the world is deeply mistaken. This book is about this conflict between manifest and physical time. The first half dives into the physics and philosophy to establish (...) the conflict’s existence; but it also argues that the claim that physics “spatializes” time is overstated. Rather, even relativity theory makes time special in deep and significant ways. The second half turns to psychology, biology, and more, seeking to understand why creatures like us develop manifest time. The novel picture that results is that manifest time is a natural reaction to the many cognitive and evolutionary challenges that we face. For subjects embedded in our circumstances, it makes sense to develop—even if fundamentally wrong. (shrink)

David Albert and Barry Loewer have argued that the temporal asymmetry of our concept of causal influence or control is grounded in the statistical mechanical assumption of a low-entropy past. In this paper I critically examine Albert's and Loewer 's accounts.

Huw Price has argued that on an interventionist account of cause the distinction is perspectival, and the claim prompted some interesting responses from interventionists and in particular an exchange with Woodward that raises questions about what it means to say that one or another structure is perspectival. I’ll introduce his reasons for claiming that the distinction between cause and effect on an interventionist account is perspectival. Then I’ll introduce a distinction between different ways in which a class of concepts can (...) be said to depend on facts about their users. Three importantly different forms of dependence will emerge from the discussion: Pragmatic dependence on us: truth conditions for x-beliefs can be given by a function f \ of more fundamental physical structures making no explicit reference to human agents. But there are any other number of functions ) ontologically on a par with x and what explains the distinguished role f plays in our practical and epistemic lives are facts about us. Implicit relativization: truth conditions for x-beliefs are relative to agent or context; the context supplies the value of a hidden parameter that determines the truth of x-beliefs. Indexicals: like implicit relativization except that the surface syntax contains a term whose semantic value is context-dependent. I suggest that Price’s insights are best understood in the first way. This will draw a crucial disanalogy with his central examples of perspectival concepts, but it will refine the thesis in a way that is more faithful to what his arguments show. The refined thesis will also support generalization to other concepts, and clarify the foundations of the quite distinctive research program that Price has been developing for a number of years. (shrink)

This article deals with the question of what time reversal means. It begins with a presentation of the standard account of time reversal, with plenty of examples, followed by a popular non-standard account. I argue that, in spite of recent commentary to the contrary, the standard approach to the meaning of time reversal is the only one that is philosophically and physically viable. The article concludes with a few open research problems about time reversal.

The final work of a distinguished physicist, this remarkable volume examines the emotive significance of time, the time order of mechanics, the time direction of thermodynamics and microstatistics, the time direction of macrostatistics, and the time of quantum physics. Coherent discussions include accounts of analytic methods of scientific philosophy in the investigation of probability, quantum mechanics, the theory of relativity, and causality. "[Reichenbach’s] best by a good deal."—Physics Today. 1971 ed.

Time is woven into the fabric of our lives. Everything we do, we do in and across time. It is not just that our lives are stretched out in time, from the moment of birth to the moment of our death. It is that our lives are stories. We make sense of ourselves, today, by understanding who we were yesterday, and the day before, and the day before that; by understanding what we did and why we did it. Our memories (...) shape our present selves, since we are the product of who we were, and who we remember being. Yet who we are lasts for but a moment. It is who we will be that demands attention. We are forever projecting ourselves into the future. We painstakingly plan for the needs of our future selves, all the while knowing that while what we do will make those future selves who they are, still, our future selves are elusive. So it is not simply that we happen to live our lives in time, the way, say, one might happen to live in Australia, or Singapore. It is hard to fathom how things could be otherwise. What would it be to live a life without time? Yet time itself is intangible. Though we are keenly aware of what has been ‒ of pain and loss, regret and pride ‒ and of what might be ‒ of anticipation, and dread, and longing ‒ time itself seems unaffected by anything we do. Though we can anticipate a future birthday cake, time itself cannot be tasted. Though we can dread a future dentist’s appointment, time itself cannot be touched. Though we remember the crunching of leaves this past autumn, time itself cannot be heard. How can it be that something so central to each of us, to who we are, and what we care about, can be so spectral? What, in the end, is time? Is time real, like a substance in which each of us, like insects in amber, finds ourselves trapped? Is time a dimension through which we can move? Is time not a thing at all, but some connection between events? If time is real, what is it like? Does it flow like a river, taking each of us prisoner in its current, washing us ever closer to the end of our lives? Is time like a cresting wave, coming ever closer to each of us from the future, engulfing us, and then receding into the past? Or is time static? Like a one-way road that each of us might wander, with no chance to turn back? Or perhaps time is like none of these things. Perhaps time is more like space; something we can navigate freely, so that we can visit different times just like we visit different places. Perhaps we can we travel in time the way we can travel in space. These questions, and many more, are the focus of this book. Now, you might wonder what philosophers are doing writing a book about time. Surely that’s a job for physicists! It is true: a great deal of what we know about time stems from our understanding of physics. However, even in physics we find that there are questions about time that go unanswered. Moreover, increasingly, physicists are turning to philosophers for help in understanding the role that time plays in current physical theories. Our goal is to get the reader up to speed on some of the central issues that influence our understanding of time so that they too may play a role in this ongoing discussion between science and philosophy. We hope that in doing so it will become clear what philosophy can bring to the study of time. There is a natural narrative in philosophy regarding the study of time, and we have chosen to organise this book according to that narrative. However, the book may also be approached in a ‘choose-your-own adventure’ spirit. While later chapters build on material introduced in earlier chapters, you can skip around, reading the book in any order you choose. For the instructor, this means that she can design her course around this book in any number of ways, depending on the particular topic she wishes to focus on. (shrink)

The paper has two parts: First, I describe a relatively popular thesis in the philosophy of propositional attitudes, worthy of the name ‘taking tense seriously’; and I distinguish it from a family of views in the metaphysics of time, namely, the A-theories (or what are sometimes called ‘tensed theories of time’). Once the distinction is in focus, a skeptical worry arises. Some A-theorists maintain that the difference between past, present, and future, is to be drawn in terms of what exists: (...) growing-block theorists eschew ontological commitment to future entities; presentists, to future and past entities. Others think of themselves as A-theorists but exclude no past or future things from their ontology. The metaphysical skeptic suspects that their attempt to articulate an ‘eternalist’ version of the A-theory collapses into merely ‘taking tense seriously’– a thesis that does not imply the A-theory. The second half of the paper is the search for a stable eternalist A-theory. It includes discussion of temporary intrinsics, temporal parts, and truth. (shrink)

A time-symmetric formulation of nonrelativistic quantum mechanics is developed by applying two consecutive boundary conditions onto solutions of a time- symmetrized wave equation. From known probabilities in ordinary quantum mechanics, a time-symmetric parameter P0 is then derived that properly weights the likelihood of any complete sequence of measurement outcomes on a quantum system. The results appear to match standard quantum mechanics, but do so without requiring a time-asymmetric collapse of the wavefunction upon measurement, thereby realigning quantum mechanics with an important (...) fundamental symmetry. (shrink)

The aim of this article is to analyse the relation between the second law of thermodynamics and the so-called arrow of time. For this purpose, a number of different aspects in this arrow of time are distinguished, in particular those of time-reversal (non-)invariance and of (ir)reversibility. Next I review versions of the second law in the work of Carnot, Clausius, Kelvin, Planck, Gibbs, Caratheodory and Lieb and Yngvason, and investigate their connection with these aspects of the arrow of time. It (...) is shown that this connection varies a great deal along with these formulations of the second law. According to the famous formulation by Planck, the second law expresses the irreversibility of natural processes. But in many other formulations irreversibility or even time-reversal non-invariance plays no role. I therefore argue for the view that the second law has nothing to do with the arrow of time. (shrink)

The aim of this paper is to construct a version of Bohm’s model that also includes the existence of backwards-in-time influences in addition to the usual forwards causation. The motivation for this extension is to remove the need in the existing model for a preferred reference frame. As is well known, Bohm’s explanation for the nonlocality of Bell’s theorem necessarily involves instantaneous changes being produced at space-like separations, in conflict with the “spirit” of special relativity even though these changes are (...) not directly observable. While this mechanism is quite adequate from a purely empirical perspective, the overwhelming experimental success of special relativity (together with the theory’s natural attractiveness), makes one reluctant to abandon it even at a “hidden” level. There are, of course, trade-offs to be made in formulating an alternative model and it is ultimately a matter of taste as to which is preferred. However, constructing an explicit example of a causally symmetric formalism allows the pros and cons of each version to be compared and highlights the consequences of imposing such symmetry. In particular, in addition to providing a natural explanation for Bell nonlocality, the new model allows us to define and work with a mathematical description in 3-dimensional space, rather than configuration space, even in the correlated many-particle case. (shrink)

A system whose expected state changes with time cannot have both a forward-directed translationally invariant probabilistic law and a backward-directed translationally invariant law. When faced with this choice, science seems to favor the former. An asymmetry between cause and effect may help to explain why temporally oriented laws are usually forward-directed.

We articulate the problems posed by the quantum liar experiment (QLE) for backwards causation interpretations of quantum mechanics, time-symmetric accounts and other dynamically oriented local hidden variable theories. We show that such accounts cannot save locality in the case of QLE merely by giving up “lambda-independence.” In contrast, we show that QLE poses no problems for our acausal Relational Blockworld interpretation of quantum mechanics, which invokes instead adynamical global constraints to explain Einstein–Podolsky–Rosen (EPR) correlations and QLE. We make the case (...) that the acausal and adynamical perspective is more fundamental and that dynamical entities obeying dynamical laws are emergent features grounded therein. (shrink)

This paper is a tour of how the laws of nature can distinguish between the past and the future, or be T-violating. I argue that, in terms of the basic argumentative structure, there are basically just three approaches currently being explored. The first is an application of Curie's Principle, together with the CPT theorem. The second route makes use of a principle due to Pasha Kabir which allows for a direct detection. The third route makes use of a Non-degeneracy Principle, (...) and is related to the energy spectrum of elementary particles. I show how each provides a general template for detecting T-violation, illustrate each with an example, and discuss their prospects in extensions of particle physics beyond the standard model. (shrink)

The nature of experience has been held to be a major reason for accepting the A-theory of time. I argue, however, that experience does not favour the A-theory over the B-theory; and that even if the A-theory were true it would not be possible to perceive the passage of time. The main argument for this draws on the constraint that a satisfactory theory of perception must explain why phenomenal characters map uniquely onto perceived worldly features. Thus, if passage is perceived, (...) it must be explained what makes one phenomenal character rather than another a perception of passage; and it must also be explained why that phenomenal character is a perception of passage rather than of some other feature of the world. I argue that no such explanation can be given, and consequently that passage cannot be perceived. I conclude that the A-theory is rendered unintelligible, and should therefore be rejected. (shrink)

Physics takes for granted that interacting physical systems with no common history are independent, before their interaction. This principle is time-asymmetric, for no such restriction applies to systems with no common future, after an interaction. The time-asymmetry is normally attributed to boundary conditions. I argue that there are two distinct independence principles of this kind at work in contemporary physics, one of which cannot be attributed to boundary conditions, and therefore conflicts with the assumed T (or CPT) symmetry of microphysics. (...) I note that this may have interesting ramifications in quantum mechanics. (shrink)