The Great Divide in metaphysical debates about laws of nature is between Humeans, who think that laws merely describe the distribution of matter, and non-Humeans, who think that laws govern it. The metaphysics can place demands on the proper formulations of physical theories. It is sometimes assumed that the governing view requires a fundamental / intrinsic direction of time: to govern, laws must be dynamical, producing later states of the world from earlier ones, in accord with the fundamental (...) direction of time in the universe. In this paper, we propose a minimal primitivism about laws of nature (MinP) according to which there is no such requirement. On our view, laws govern by constraining the physical possibilities. Our view captures the essence of the governing view without taking on extraneous commitments about the direction of time or dynamic production. Moreover, as a version of primitivism, our view requires no reduction / analysis of laws in terms of universals, powers, or dispositions. Our view accommodates several potential candidates for fundamental laws, including the principle of least action, the Past Hypothesis, the Einstein equation of general relativity, and even controversial examples found in the Wheeler-Feynman theory of electrodynamics and retrocausal theories of quantum mechanics. By understanding governing as constraining, non-Humeans who accept MinP have the same freedom to contemplate a wide variety of candidate fundamental laws as Humeans do. (shrink)

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.

The aim of this essay is to introduce philosophers of science to some recent philosophical discussions of the nature and origin of the direction of time. The essay is organized around books by Hans Reichenbach, Paul Horwich, and Huw Price. I outline their major arguments and treat certain critical points in detail. I speculate at the end about the ways in which the subject may continue to develop and in which it may connect with other areas of philosophy.

The problem of the direction of time is reconsidered in the light of a generalized version of the theory of abstract deterministic dynamical systems, thanks to which the mathematical model of time can be provided with an internal dynamics, solely depending on its algebraic structure. This result calls for a reinterpretation of the directional properties of physical time, which have been typically understood in a strictly topological sense, as well as for a reexamination of the theoretical (...) meaning of the widespread time-reversal invariance of classical physical processes. (shrink)

The meaning of the phrase “the direction of time” and the physical problems involved are considered. These problems are discussed and plausibility arguments are given to show that all clocks run in the same direction (almost always), that the most probable development of the Universe during the early stages of the expansion would result in the introduction of some internal organization, and that the expansion of the Universe and the increase in entropy define time directions that (...) have the same sense. The question of what properties of the laws governing the Universe lead to these results is studied. (shrink)

Macroscopic irreversible processes emerge from fundamental physical laws of reversible character. The source of the local irreversibility seems to be not in the laws themselves but in the initial and boundary conditions of the equations that represent the laws. In this work we propose that the screening of currents by black hole event horizons determines, locally, a preferred direction for the flux of electromagnetic energy. We study the growth of black hole event horizons due to the cosmological expansion and (...) accretion of cosmic microwave background radiation, for different cosmological models. We propose generalized McVittie co-moving metrics and integrate the rate of accretion of cosmic microwave background radiation onto a supermassive black hole over cosmic time. We find that for flat, open, and closed Friedmann cosmological models, the ratio of the total area of the black hole event horizons with respect to the area of a radial co-moving space-like hypersurface always increases. Since accretion of cosmic radiation sets an absolute lower limit to the total matter accreted by black holes, this implies that the causal past and future are not mirror symmetric for any spacetime event. The asymmetry causes a net Poynting flux in the global future direction; the latter is in turn related to the ever increasing thermodynamic entropy. Thus, we expose a connection between four different “time arrows”: cosmological, electromagnetic, gravitational, and thermodynamic. (shrink)

The question why natural processes tend to flow along a preferred direction has always been considered from within the perspective of the Second Law of Thermodynamics, especially its statistical formulation due to Maxwell and Boltzmann. In this article, we re-examine the subject from the perspective of a new historico-philosophical formulation based on the careful use of selected theoretical elements taken from three key modern thinkers: Hans Reichenbach, Ilya Prigogine, and Roger Penrose, who are seldom considered together in the literature. (...) We emphasize in our analysis how the entropy concept was introduced in response to the desire to extend the applicability of the Second Law to the cosmos at large (Reichenbach and Penrose), and to examine whether intrinsic irreversibility is a fundamental universal characteristics of nature (Prigogine). While the three thinkers operate with vastly different technical proposals and belong to quite distinct intellectual backgrounds, some similarities are detected in their thinking. We philosophically examine these similarities but also bring into focus the uniqueness of each approach. Our purpose is not providing an exhaustive derivations of logical concepts identified in one thinker in terms of ideas found in the others. Instead, the main objective of this work is to stimulate historico-philosophical investigations and inquiries into the problem of the direction of time in nature by way of crossdisciplinary examinations of previous theories commonly treated in literature as disparate domains. (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.

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)

Reichenbach explains temporally asymmetric phenomena by appeal to entropy and ‘branch structure’. He explains why the entropic gradients of isolated subsystems are oriented towards the future and not the past, and why we have records of the past and not the future, by appeal to the fact that the universe is currently on a long entropic upgrade with subsystems that branch off and become quasi-isolated. Reichenbach’s approach has been criticised for relying too closely on entropy. The more popular approach nowadays (...) is to appeal instead to a particular low-entropy initial state—Albert’s ‘Past Hypothesis’. I’ll argue that this neglect of Reichenbach’s approach is unwarranted. A Reichenbachian account has important advantages over Albert’s: it correctly identifies the minimal temporally asymmetric posit needed to derive key temporally asymmetries and it offers a more adequate account of the record asymmetry. While a Reichenbachian account needs to be supplemented, it provides the right foundations for explaining temporally asymmetric phenomena and what we might ultimately mean by ‘the direction of time’. (shrink)

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 seems that time has direction which points ahead from the past to the future. Traditionally, the main efforts to explain the arrow of time were carried out within the domain of physics, primarily utilizing statistical mechanics laws. Here, I attempt to explain how the forward direction of time is configured from the viewpoint of the mind. At first impression the concept of forward direction stems from the meeting of subjectivity with space and as (...) such it is applied to time. However, I show that the forward direction of time has a unique temporal sense not derived from space. Later I relate phenomenological explanations of the flow of time to the direction of time. (shrink)

The impression is frequently given that the static description of the 4-dimensional world given by a tenseless theory of time adequately accounts for the world and that a tensed theory of time has nothing to offer. In fact, the tenseless theory of time leaves us incapable of specifying the direction of time, whereas a tensed theory of time enables us to do so. Thus, the tensed theory enjoys a considerable advantage over the tenseless view.

A detailed attempt to ground the topological properties of time in the laws of micro- and macro-physical processes. The reversible processes of mechanics are used to define an order among temporally separated events, which is invariant under reversals of time direction. So long as consideration is limited to a single isolated system, a time ensemble, the transfer of the reversibility of the constituent processes of such a system to the system as a whole makes it impossible (...) to define time direction by means of the entropy curve. The directionality of time, accordingly, can only be defined as the direction of the entropy increase of multiple systems, of a space ensemble. A macrostatistical definition of time direction is then based upon the causal relation. The author's view of causation is non-deterministic: the conjunction of two events is caused if they occur together more frequently than can be expected from their chance coincidence. Reichenbach's analyses and arguments are careful and thorough; the book as a whole is a solid achievement. -- M. F. (shrink)

In recent papers the authors have discussed the dynamical properties of “large Poincaré systems” (LPS), that is, nonintegrable systems with a continuous spectrum (both classical and quantum). An interesting example of LPS is given by the Friedrichs model of field theory. As is well known, perturbation methods analytic in the coupling constant diverge because of resonant denominators. We show that this Poincaré “catastrophe” can be eliminated by a natural time ordering of the dynamical states. We obtain then a dynamical (...) theory which incorporates a privileged direction of time (and therefore the second law of thermodynamics). However, it is only in very simple situations that this time ordering can be performed in an “extended” Hilbert space. In general, we need to go to the Liouville space (superspace) and introduce a time ordering of dynamical states according to the number of particles involved in correlations. This leads then to a generalization of quantum mechanics in which the usual Heisenberg's eigenvalue problem is replaced by a complex eigenvalue problem in the Liouville space. (shrink)

I argue that in the many worlds interpretation of quantum mechanics time has no fundamental direction. I further discuss a way to recover thermodynamics in this interpretation using decoherence theory (Zurek and Paz 1994). Albert's proposal to recover thermodynamics from the collapse theory of Ghirardi et al. (1986) is also considered.

It is argued that the main problem with "the problem of the direction of time" is to figure out what the problem is or is supposed to be. Towards this end, an attempt is made to disentangle and to classify some of the many issues which have been discussed under the label of 'the direction of time'. Secondly, some technical apparatus is introduced in the hope of producing a sharper formulation of the issues than they have (...) received in the philosophical literature. Finally, some tentative suggestions about the central issues are offered. In particular, it is suggested that entropy and irreversibility are much less crucial to the central issues than most philosophers would have us believe. This suggestion is not made because of any firm conviction of its correctness but rather because it helps to focus the discussion on some basic but long neglected assumptions which underlie traditional approaches. (shrink)

While experience tells us that time flows from the past to the present and into the future, a number of philosophical and physical objections exist to this commonsense view of dynamic time. In an attempt to make sense of this conundrum, philosophers and physicists are forced to confront fascinating questions, such as: Can effects precede causes? Can one travel in time? Can the expansion of the Universe or the process of measurement in quantum mechanics define a (...) class='Hi'>direction in time? In this book, researchers from both physics and philosophy attempt to answer these issues in an interesting, yet rigorous way. This fascinating book will be of interest to physicists and philosophers of science and educated general readers interested in the direction of time. (shrink)

In lieu of an abstract, here is a brief excerpt of the content:Convention for Protection of Human Rights and Dignity of the Human Being with Regard to the Application of Biology and Biomedicine: Convention on Human Rights and BiomedicineCouncil of EuropePreambleThe Member States of the Council of Europe, the other States and the European Community signatories hereto,Bearing in mind the Universal Declaration of Human Rights proclaimed by the General Assembly of the United Nations on 10 December 1948;Bearing in mind the (...) Convention for the Protection of Human Rights and Fundamental Freedoms of 4 November 1950;Bearing in mind the European Social Charter of 18 October 1961;Bearing in mind the International Covenant on Civil and Political Rights and the International Covenant on Economic, Social and Cultural Rights of 16 December 1966;Bearing in mind the Convention for the Protection of Individuals with Regard to Automatic Processing of Personal Data of 28 January 1981;Bearing also in mind the Convention on the Rights of the Child of 20 November 1989;Considering that the aim of the Council of Europe is the achievement of a greater unity between its members and that one of the methods by which that aim is to be pursued is the maintenance and further realisation of human rights and fundamental freedoms;Conscious of the accelerating developments in biology and medicine;Convinced of the need to respect the human being both as an individual and as a member of the human species and recognising the importance of ensuring the dignity of the human being; [End Page 277]Conscious that the misuse of biology and medicine may lead to acts endangering human dignity;Affirming that progress in biology and medicine should be used for the benefit of present and future generations;Stressing the need for international co-operation so that all humanity may enjoy the benefits of biology and medicine;Recognising the importance of promoting a public debate on the questions posed by the application of biology and medicine and the responses to be given thereto;Wishing to remind all members of society of their rights and responsibilities;Taking account of the work of the Parliamentary Assembly in this field, including Recommendation 1160 (1991) on the preparation of a Convention on bioethics;Resolving to take such measures as are necessary to safeguard human dignity and the fundamental rights and freedoms of the individual with regard to the application of biology and medicine;Have agreed as follows:Chapter IGeneral provisionsArticle 1. (Purpose and object)Parties to this Convention shall protect the dignity and identity of all human beings and guarantee everyone, without discrimination, respect for their integrity and other rights and fundamental freedoms with regard to the application of biology and medicine.Each Party shall take in its internal law the necessary measures to give effect to the provisions of this Convention.Article 2. (Primacy of the human being)The interests and welfare of the human being shall prevail over the sole interest of society or science.Article 3. (Equitable access to health care)Parties, taking into account health needs and available resources, shall take appropriate measures with a view to providing, within their jurisdiction, equitable access to health care of appropriate quality. [End Page 278]Article 4. (Professional standards)Any intervention in the health field, including research, must be carried out in accordance with relevant professional obligations and standards.Chapter IIConsentArticle 5. (General rule)An intervention in the health field may only be carried out after the person concerned has given free and informed consent to it.This person shall beforehand be given appropriate information as to the purpose and nature of the intervention as well as on its consequences and risks.The person concerned may freely withdraw consent at any time.Article 6. (Protection of persons not able to consent)1. Subject to Articles 17 and 20 below, an intervention may only be carried out on a person who does not have the capacity to consent, for his or her direct benefit.2. Where, according to law, a minor does not have the capacity to consent to an intervention, the intervention may only be carried out with the authorisation of his or her representative or an authority or a person or... (shrink)

This paper searches for an explicit expression of the so-called problem of the direction of time. I argue that the traditional version of the problem is an artifact of a mistaken view in the foundations of statistical mechanics, and that to the degree it is a problem, it is really one general to all the special sciences. I then search the residue of the traditional problem for any remaining difficulty particular to time's arrow and find that there (...) is a special puzzle for some types of scientific realist. (shrink)

This paper defends Aristotle’s project of deriving the order of time from the order of change in Physics 4.11, against the objection that it contains a vicious circularity arising from the assumption that we cannot specify the direction of a change without invoking the temporal relations of its stages. It considers and rejects a solution to this objection proposed by Ursula Coope, and proposes an alternative solution. It also considers the related problem of how the temporal orders and (...) directions derived from individual changes can together constitute a single, globally consistent order and direction of time. (shrink)

The social sciences playa variety of multifaceted roles in the policymaking process. So varied are these roles, indeed, that it is futile to talk in the singular about the use of social science in policymaking, as if there were one constant relationship between two fixed and stable entities. Instead, to address this issue sensibly one must talk in the plural about uses of dif ferent modes of social scientific inquiry for different kinds of policies under various circumstances. In some cases, (...) the influence of social scientific research is direct and tangible, and the connection between the find ings and the policy is easy to see. In other cases, perhaps most, its influence is indirect-one small piece in a larger mosaic of politics, bargaining, and compromise. Occasionally the findings of social scientific studies are explicitly drawn upon by policymakers in the formation, implementation, or evaluation of particular policies. More often, the categories and theoretical models of social science provide a general background orientation within which policymakers concep tualize problems and frame policy options. At times, the in fluence of social scientific work is cognitive and informational in nature; in other instances, policymakers use social science primarily for symbolic and political purposes in order to le gitimate preestablished goals and strategies. Nonetheless, amid this diversity and variety, troubling general questions persistently arise. (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)

One of the questions that is addressed, from various perspectives, is the origin of time-asymmetry. Given the time-symmetry of the dynamical laws, all inferences about the future that are derivable from a dynamical theory are matched by inferences about the past. For Huw Price, who discusses the origins of cosmological time asymmetry, this is reason to treat all time-asymmetric cosmological theories with caution. He dismisses both the inflationary model and Stephen Hawking’s proposal to account for (...) class='Hi'>time-asymmetry with his famous “no boundary condition.” Instead, on the basis of the fact that we have no a priori reasons to distinguish between initial and final conditions, he advocates Gold’s time-symmetric model for the universe, in which the thermodynamical arrow of time is tied to the expansion of the universe, so that in the contracting phase towards the big crunch, entropy decreases. (shrink)

A probabilistic theory of causation is a theory which holds that the central feature of causation is that causes raise the probability of their effects. In this dissertation, I defend Hans Reichenbach's original version of the probabilistic theory of causation, which analyses causal relations in terms of a three place statistical betweenness relation. Unlike most discussions of this theory, I hold that the statistical relation should be taken as a sufficient, but not as a necessary , condition for causal betweenness. (...) With this difference in interpretation, Reichenbach's theory is shown to be immune to all of the criticisms which have been raised against it in the last fifty years. ;Reichenbach's main purpose in defending a probabilistic theory of causation was to use it in giving an analysis of the direction of time. I defend this view, arguing that the arrow of causation is more basic than any of the other arrows of time---metaphysical, psychological or physical. In particular, I argue against the popular view that the direction of time is given by the physical fact that entropy only increases in one direction. I further show that the probabilistic theory of causation is particularly suited to the task of analysing the various arrows of time. In my final chapter, I also suggest that the probabilistic theory of causation may be fruitfully applied to the analysis of some important puzzles in the interpretation of quantum mechanics. (shrink)

This thesis introduces and defends a ‘C theory’ of time. The metaphysics of time literature is primarily concerned with the distinction between the A and B theories of time, with the disagreement concerning whether the passage of time is an objective feature of reality. I argue that the distinction between the B and C theories—in terms of whether time has a ‘privileged’ direction—is of more obvious relevance to the philosophy of physics than is the (...) distinction between the A and B theories. The thesis has three main contentions. (1) In order to maintain a substantial metaphysical dispute between the different theories of time, they must be defined in terms of structural properties, and the naturalistic metaphysics of time direction involves the assessment of these structures in light of contemporary physics. (2) The A theory of time requires a model with two temporal dimensions, and although such a model provides a resolution to a number of problems faced by standard A theories, it is not motivated by physical theory. (3) The dispute between the B and C theories of time is of direct relevance to the philosophy of physics: the B theorist’s assumption of the existence of a privileged temporal direction is of explanatory relevance to physics; and a comparison between unidirectional and adirectional explanations in physics can in principle shed light on whether time is B- or C-theoretic. (shrink)