Alison Sutton Fernandes

Does time have a direction in and of itself? Using metaphysics guided by science, our reasons for thinking time might have an intrinsic direction fall into two types, demarcating two “projects”. We might posit an intrinsic direction a) to explain temporal asymmetries (the explanatory project) or b) as a precondition for temporally asymmetric fundamental dynamical laws (the precondition project). A common thought is that no direction of time is required in the explanatory project, but that we should be agnostic over whether such a direction is required in the precondition project. I’ll argue that such a position is unstable. The arguments for an intrinsic direction in the precondition project would, if they worked, apply equally to the explanatory project. Conversely, if one denies that the explanatory project supports an intrinsic direction of time, one can’t, given current arguments, accept that an intrinsic direction of time might be supported in the precondition project. I’ll suggest a shared resolution to both projects: neither temporally asymmetric laws nor boundary conditions require an intrinsic direction of time. This resolution suggests a further plausible view: there could never be scientific reason to posit an intrinsic direction of time, even though such a direction is conceptually coherent.

There are temporal asymmetries in our attitudes, including certain ways in which we seem to care more about events that happen in the future rather than the past. According to the Simple Causal Account, we care more about future events because we can (potentially) influence future events but cannot (even in principle) influence past events. This chapter defends an alternative Enriched Causal Account, according to which we care more about future events because they happen to our ‘causally later’ selves—temporal parts of ourselves that are ‘later’, given the causal ordering that underlies personal identity. This Enriched Causal Account recovers our intuitive judgements in a wider variety of cases and fits with evolutionary explanations and empirical work. Overall, it points towards the need to pay more attention to our causal connectedness through time to explain temporal asymmetries in our attitudes.

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’.

When we deliberate about what to do, we appear to be free to decide on different options. Three accounts use ordinary beliefs to explain this apparent freedom—appealing to different types of ‘epistemic freedom’. When an agent has epistemic freedom, her evidence while deliberating does not determine what decision she makes. This ‘epistemic gap’ between her evidence and decision explains why her decision appears free. The varieties of epistemic freedom appealed to might look similar. But there is an important difference. Two rely on an agent's ability to justifiably form beliefs unconstrained by evidence, and identify decisions as beliefs—either beliefs about acts or about decisions. But, when used to explain apparent freedom, these accounts face serious problems: they imply that agents have epistemic freedom over evidence-based beliefs, and rely on a faulty notion of justification. Underlying these troubles, it turns out that these accounts presuppose an unexplained apparent ability to form different beliefs. A third variety of epistemic freedom uses ignorance conditions instead (Levi and Kapitan). We appear free partly because we’re ignorant of what we’ll decide. Ignorance-based accounts avoid the above problems, and remain a promising alternative.

David Albert explains why we can typically influence the future but not the past by appealing to an initial low-entropy state of the universe. And he argues that in the rare cases where we can influence the past, we cannot use this influence to knowingly gain future rewards: so it does not constitute control. I introduce an important new case in which Albert's account implies we can not only influence the past but control it: a case where our actions in the present are reliably correlated with several events in the present and past. To deal with such cases, we need to appeal to epistemic conditions on deliberation: being agents requires our decisions being epistemically undetermined at the time we make them. In a world with the past-hypothesis, this implies that deliberation will typically come prior to decision. Once deliberation in this direction is established, correlations towards the past cannot then be exploited for control. To explain why we cannot effectively control the past, we need to appeal to deliberation, whether as part of a defence of Albert's account, or used independently to explain the asymmetry of control.

A plausible thought is that we should evaluate counterfactuals in the actual world by holding the present ‘fixed’; the state of the counterfactual world at the time of the antecedent, outside the area of the antecedent, is required to match that of the actual world. When used to evaluate counterfactuals in the actual world, this requirement may produce reasonable results. However, the requirement is deeply problematic when used in the context of explaining causal asymmetry (why causes come before their effects). The requirement plays a crucial role in certain statistical mechanical explanations of the temporal asymmetry of causation. I will use a case of backwards time travel to show how the requirement enforces certain features of counterfactual structure a priori. For this reason, the requirement cannot be part of a completely general method of evaluating counterfactuals. More importantly, the way the requirement enforces features of counterfactual structure prevents counterfactual structure being derived from more fundamental physical structure—as explanations of causal asymmetry demand. Therefore, the requirement cannot be used when explaining causal asymmetry. To explain causal asymmetry, we need more temporally neutral methods for evaluating counterfactuals—those that produce the right results in cases involving backwards time travel, as well as in the actual world.

Causes always seem to come prior to their effects. What might explain this asymmetry? Causation's temporal asymmetry isn't straightforwardly due to a temporal asymmetry in the laws of nature—the laws are, by and large, temporally symmetric. Nor does the asymmetry appear due to an asymmetry in time itself. This Element examines recent empirical attempts to explain the temporal asymmetry of causation: statistical mechanical accounts, agency accounts and fork asymmetry accounts. None of these accounts are complete yet and a full explanation of the temporal asymmetry of causation will likely require contributions from all three programs.

Do time travellers retain their normal freedom and abilities when they travel back in time? Lewis, Horwich and Sider argue that they do. Time-travelling Tim can kill his young grandfather, his younger self, or whomever else he pleases—and so, it seems can reasonably deliberate about whether to do these things. He might not succeed. But he is still just as free as a non-time traveller. I’ll disagree. The freedom of time travellers is limited by a rational constraint. Tim can’t reasonably deliberate on killing his grandfather, certain that he’ll fail. If Tim follows his evidence, and appropriately self-predicts, he will be certain he won’t kill his grandfather. So if Tim is both evidentially and deliberatively rational, he can’t deliberate on killing his grandfather. This result has consequences. Firstly, it shows how evidential limits in the actual world contribute to our conception of the future as open. Secondly, it undercuts arguments against the possibility of time travel. Thirdly, it affects how we evaluate counterfactuals in time travel worlds, as well as our own. I’ll use the constraint to motivate an evidential and temporally neutral method of evaluating counterfactuals that holds fixed what a relevant deliberating agent has evidence of, independently of her decision. Using this method, an agent’s local abilities may be affected by what happens globally at other times, including the future.

We standardly evaluate counterfactuals and abilities in temporally asymmetric terms—by keeping the past fixed and holding the future open. Only future events depend counterfactually on what happens now. Past events do not. Conversely, past events are relevant to what abilities one has now in a way that future events are not. Lewis, Sider and others continue to evaluate counterfactuals and abilities in temporally asymmetric terms, even in cases of backwards time travel. I’ll argue that we need more temporally neutral methods. The past shouldn’t always be held fixed, because backwards time travel requires backwards counterfactual dependence. Future events should sometimes be held fixed, because they’re in the causal history of the past, and agents have evidence of them independently of their decisions now. We need temporally neutral methods to maintain connections between causation, counterfactuals and evidence, and if counterfactuals are used to explain the temporal asymmetry of causation.

There are temporal asymmetries in our attitudes towards the past and future. For example, we judge that a given amount of work is worth twice as much if it is described as taking place in the future, compared to the past :796–801, 2008). Does this temporal value asymmetry support a tensed metaphysics? By getting clear on the asymmetry’s features, I’ll argue that it doesn’t. To support a tensed metaphysics, the value asymmetry would need to not vary with temporal distance, apply equally to events concerning oneself and others, and be rational and judged to be so. But evidence suggests the value asymmetry lacks these features. There are, moreover, independent arguments against its rationality. The asymmetry’s features suggest instead that it arises as an emotion-driven generalisation from a temporal bias concerning our future actions. This explanation points towards mechanisms that can play a role in explaining other instances where we generalise about the past and future, and why we’re tempted towards metaphysical pictures of time.

I introduce a novel method for evaluating counterfactuals. According to the branchpoint proposal, counterfactuals are evaluated by ‘rewinding’ the universe to a time at which the antecedent had a reasonable probability of coming about and considering the probability for the consequent, given the antecedent. This method avoids surprising dynamics, allows the time of the branchpoint to be determined by the system’s dynamics (rather than by context) and uses scientific posits to specify the relevant probabilities. I then show how the branchpoint proposal can be justified by considering an evidential role for counterfactuals: counterfactuals help us reason about the probabilistic relations that hold in a hypothetical scenario at which the antecedent is maximally unsettled. A result is that we should distinguish the use of counterfactuals in contexts of control from their use for reasoning evidentially. Standard Lewisian accounts run into trouble precisely by expecting a single relation to play both roles.

In this paper, I use the evidential function of chances and counterfactuals to develop accounts of these relations. Chances are objective worldly probabilities that allow us to reason from the state of a system at one time to the state of a system at another time. Counterfactuals are used to reason about what evidence we would have in hypothetical cases—and so, I’ll argue, are evaluated by considering ‘branch points’ where the counterfactual antecedent had a reasonable chance of coming about. An upshot is that counterfactuals play a distinct role from causal relations—and it was a mistake to look for a single set of probabilities that would determine both how we should reason about the world (counterfactuals) and how states of the world depend on others under conditions of manipulation (causal relations). These evidential accounts do better than nearby statistical-mechanical accounts in identifying the function of distinctly modal relations and justifying why we reason about the world in modal terms. They also do better at identifying the source of the temporal asymmetries in these relations—they are due to a probability gradient of the universe, rather than to a special initial state.