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 (according to the theory) 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 paper 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 noncausal reading, time reversal symmetry poses no significant conceptual nor epistemological problems for causation.

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" (Russell, 1913, p. 1). 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: (1) 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 (2) 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.

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.

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 Aand 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.

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.