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)

Cognitive science has recently made some startling discoveries about temporal experience, and these discoveries have been drafted into philosophical service. We survey recent appeals to cognitive science in the philosophical debate over whether time objectively passes. Since this research is currently in its infancy, we identify some directions for future research.

“The universe is expanding, not contracting.” Many statements of this form appear unambiguously true; after all, the discovery of the universe’s expansion is one of the great triumphs of empirical science. However, the statement is time-directed: the universe expands towards what we call the future; it contracts towards the past. If we deny that time has a direction, should we also deny that the universe is really expanding? This article draws together and discusses what I call ‘C-theories’ of time — (...) in short, philosophical positions that hold time lacks a direction — from different areas of the literature. I set out the various motivations, aims, and problems for C-theories, and outline different versions of antirealism about the direction of time. (shrink)

Experiences of motion and change are widely taken to have a ‘flow-like’ quality. Call this ‘temporal qualia’. Temporal qualia are commonly thought to be central to the question of whether time objectively passes: (1) passage realists take temporal passage to be necessary in order for us to have the temporal qualia we do; (2) passage antirealists typically concede that time appears to pass, as though our temporal qualia falsely represent time as passing. I reject both claims and make the case (...) that passage-talk plays no useful explanatory role with respect to temporal qualia, but rather obfuscates what the philosophical problem of temporal qualia is. I offer a ‘reductionist’ account of temporal qualia that makes no reference to the concept of passage and argue that it is well motivated by empirical studies in motion perception. (shrink)

Modern physics has provided a range of motivations for holding time to be fundamentally undirected. But how does a temporally adirectional metaphysics, or ‘C-theory’ of time, fit with the time of experience? In this chapter, I look at what kind of problem human time poses for C-theories. First, I ask whether there is a ‘hard problem’ of human time: whether it is in principle impossible to have the kinds of experience we do in a temporally adirectional world. Second I consider (...) the ‘easy problem’: how specific directed aspects of our temporal experience are to be explained by C-theorists. This leads to a greater issue: is there such a thing as an experience of time direction at all to even be explained? I show how the kinds of experience we have that we typically associate with the idea of time being directed can be accommodated within a directionless picture of time. (shrink)

Bertrand Russell famously argued that causation is not part of the fundamental physical description of the world, describing the notion of cause as “a relic of a bygone age”. This paper assesses one of Russell’s arguments for this conclusion: the ‘Directionality Argument’, which holds that the time symmetry of fundamental physics is inconsistent with the time asymmetry of causation. We claim that the coherence and success of the Directionality Argument crucially depends on the proper interpretation of the ‘ time symmetry’ (...) of fundamental physics as it appears in the argument, and offer two alternative interpretations. We argue that: if ‘ time symmetry’ is understood as the time -reversal invariance of physical theories, then the crucial premise of the Directionality Argument should be rejected; and if ‘ time symmetry’ is understood as the temporally bidirectional nomic dependence relations of physical laws, then the crucial premise of the Directionality Argument is far more plausible. We defend the second reading as continuous with Russell’s writings, and consider the consequences of the bidirectionality of nomic dependence relations in physics for the metaphysics of causation. (shrink)

It is often said that the world is explained by laws of nature together with initial conditions. But does that mean initial conditions don’t require further explanation? And does the explanatory role played by initial conditions entail or require that time has a preferred direction? This chapter looks at the use of the ‘initialness defence’ in physics, the idea that initial conditions are intrinsically special in that they don’t require further explanation, unlike the state of the world at other times. (...) Such defences commonly assume a primitive directionality of time to distinguish between initial and final conditions. Using the case study of the time-asymmetry of thermodynamics and the so-called ‘past hypothesis’ — the hypothesis that the early universe was in a state of very low entropy —, I outline and support a deflationary account of the initialness defence that does not pre- suppose a basic directionality of time, and argue that there is a relevant explanatory asymmetry between initial conditions and the state of systems at other times only if certain causal conditions are satisfied. Hence, the initialness defence is available to those who reject a fundamental direction of time. (shrink)

This paper assesses branching spacetime theories in light of metaphysical considerations concerning time. I present the A, B, and C series in terms of the temporal structure they impose on sets of events, and raise problems for two elements of extant branching spacetime theories—McCall’s ‘branch attrition’, and the ‘no backward branching’ feature of Belnap’s ‘branching space-time’—in terms of their respective A- and B-theoretic nature. I argue that McCall’s presentation of branch attrition can only be coherently formulated on a model with (...) at least two temporal dimensions, and that this results in severing the link between branch attrition and the flow of time. I argue that ‘no backward branching’ prohibits Belnap’s theory from capturing the modal content of indeterministic physical theories, and results in it ascribing to the world a time-asymmetric modal structure that lacks physical justification. (shrink)

In what sense is the direction of time a matter of convention? In 'The Direction of Time', Hans Reichenbach makes brief reference to parallels between his views about the status of time’s direction and his conventionalism about geometry. In this article, I: (1) provide a conventionalist account of time direction motivated by a number of Reichenbach’s claims in the book; (2) show how forwards and backwards time can give equivalent descriptions of the world despite the former being the ‘natural’ direction (...) of time; and (3) argue that this offers an important middle-ground position between existing realist and antirealist accounts of the direction of time. (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)

In the two feature articles for this volume, Gruber et al and Buonomano & Rovelli focus on what the former call the 'two-times problem', in short, the apparent lack of fit between time as described by physical science and our own temporal experience, where 'experience' involves things like memory, anticipation, and perception of change and motion. In this short note I'll make the case that the twotimes problem is less serious than it is often made out to be in the (...) specific case of features like 'passage ' and 'presentness' that are central to the 'A-theory' of time ---the theory that holds time to be composed of dynamic regions of 'past', 'present' and future', and for time to genuinely flow or pass.My contention is three-fold: (1) the two-times problem is better understood as a three-times problem: rather than a conflict between 'physical' and 'manifest' time, what we have in the case of time is differences between the time of physics, the time of experience, and the 'folk' concept of time. (2) Understanding the problem in this way helps deflate certain problems about the relationship of these three pictures; the time of experience and the time of physics are less obviously in a problematic conflict than often supposed; and the folk concept of time is what brings in problematic features of time hard to fit with either the time of physics of experience. (3) Understanding the time of experience as independent from the folk concept of time better fits the actual aims of the... (shrink)

Whatever you think of Bertrand Russell’s famous claim that the ‘law of causality’ is (at least as of 1912) redundant in the ‘advanced sciences’, it is nonethele.

It is an unresolved question in quantum mechanics whether quantum states apply to individual quantum systems, or to ensembles of quantum systems. We show by way of a thought experiment that quantum states apply only to ensembles of quantum systems. A further unresolved question is whether quantum systems possess ontic states. If a quantum state is the state of an ensemble, as we claim, the answer to this question is that quantum states are not ontic. However, a notable recent result (...) in quantum foundations shows that if there are any ontic states at all, then the quantum state must be ontic. Collectively, these two results imply that there are no ontic states. We examine the assumptions required for these results, and suggest that the retrospective effect on state preparations by entangling measurements provides good reason for relaxing the assumption of preparation independence at the ontic level. (shrink)

While science is taken to differ from non-scientific activities in virtue of its methodology, metaphysics is usually defined in terms of its subject matter. However, many traditional questions of metaphysics are addressed in a variety of ways by science, making it difficult to demarcate metaphysics from science solely in terms of their subject matter. Are the methodologies of science and metaphysics sufficiently distinct to act as criteria of demarcation between the two? In this chapter we focus on several important overlaps (...) in the methodologies used within science and metaphysics in order to argue that focusing solely on methodology is insufficient to offer a sharp demarcation between metaphysics and science, and consider the consequences of this for the wider relationship between science and metaphysics. (shrink)

Review of 'Causal Reasoning in Physics' by Mathias Frisch for British Journal for Philosophy of Science.

A review of Tim Maudlin's "Philosophy of Physics: Space and Time".