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Higher-order evidence is evidence about what is rational to think in light of your evidence. Many have argued that it is special – falling into its own evidential category, or leading to deviations from standard rational norms. But it is not. Given standard assumptions, almost all evidence is (in part) higher-order evidence.

I defend counterfactual decision theory, which says that you should evaluate an action in terms of which outcomes would likely obtain were you to perform it. Counterfactual decision theory has traditionally been subsumed under causal decision theory as a particular formulation of the latter. This is a mistake. Counterfactual decision theory is importantly different from, and superior to, causal decision theory, properly so called. Causation and counterfactuals come apart in three kinds of cases. In cases of overdetermination, an action can cause a good outcome without the latter counterfactually depending on the former. In cases of constitution, an action can constitute a good outcome rather than causing it. And in cases of determinism, either the laws or the past counterfactually depend on your action, even though your action cannot cause the laws or the past to be different. In each of these cases, it is counterfactual decision theory which gives the right verdict, and for the right reasons.

Many consequentialists argue that you ought to do your part in collective action problems like climate change mitigation because (i) all such problems are triggering cases and (ii) doing your part in a triggering case maximizes expected value. I show that both (i) and (ii) are false: Some triggering cases cannot be solved by appeal to expected value, since they involve infinities, and some collective action problems are not triggering cases, since they involve parity. Nonetheless, consequentialism will still prohibit failure to do your part in many collective action problems where we believe that so acting would be impermissible.

Many requirements of rationality rely for their application on facts about identity at a time. Take the requirement not to have contradictory beliefs. It is irrational if a single agent believes P and believes ¬P, but it is not irrational if one agent believes P and another believes ¬P. There are puzzle cases, however, in which it is unclear whether we have a single agent, or instead two or more. I consider and reject possible criteria of identity at a time before proposing a pluralist alternative on which there are vastly more agents than we might have thought. This pluralist thesis is analogous to mereological universalism, on which there are all sorts of strange disconnected objects we don’t usually take note of. I conclude by giving a pragmatic account of which of these rational agents it makes sense to attend to by appealing the purposes we have in employing rationally evaluative language.

If groups can have beliefs and other attitudes of their own, what determines which such attitudes the group rationally ought to have? A widespread presupposition is that group-level beliefs should be a function of the beliefs of the group’s members, and similarly for other attitudes. But a host of impossibility theorems show that no such aggregation function can satisfy intuitively attractive constraints while ensuring coherent group-level attitudes. I argue that this presupposition is false. Group-level attitudes should be a function of group-level reasons (evidence, in the epistemic case), not individual-level attitudes. This allows for a theory of group rationality that (i) bypasses a host of pessimistic results in the literature on judgment aggregation and (ii) treats rational individual-level attitudes and rational group-level attitudes in parallel.

In their contributions to this symposium, D¨oring and Eker, Snedegar, and Lenman advance a variety of objections to the time-slice-centric theory of rationality I defend in Reasons without Persons. I am grateful for their thoughtful and incisive comments. I consider their arguments in turn.

What form should jury decision-making take? In particular, should juries be permitted—even encouraged or required—to make their decisions by means of free, unstructured deliberation? In this paper, I argue that juries should not engage in such deliberations on the way to reaching a verdict. In particular, I argue that jury deliberation is problematic on both theoretical and empirical grounds. On the theoretical front, deliberation destroys the independence of jurors’ judgments that is needed for certain theoretical results (in particular, the Condorcet Jury Theorem) to be applicable. On the empirical front, there is evidence from both legal and non-legal contexts that unstructured group deliberation leads to group judgments that are worse in a number of respects than judgments generated by non-deliberative methods of judgment aggregation. Finally, I examine some possible alternatives to unstructured deliberation, including the constrained, structured deliberation embodied in the DELPHI method, voting (without deliberation), and averaging of probabilistic judgments

I have advocated a time-slice-centric model of rationality, according to which there are no diachronic requirements of rationality. Podgorski (2016) challenges this picture on the grounds that temporally extended mental processes are epistemically important, rationally evaluable, and governed by diachronic requirements. I argue that the particular cases that Podgorski marshals to make his case are unconvincing, but that his general challenge might motivate countenancing rational requirements on processes like reasoning. However, so long as such diachronic requirements are merely derivative of more fundamental synchronic requirements, so that a pattern of reasoning counts as rational or irrational only in so far as it tends to lead one to better satisfy these fundamental synchronic requirements, we can meet Podgorski’s challenge without significantly deviating from a time-slice-centric approach to epistemology.

Objectivism about evidential support is the thesis that facts about the degree to which a body of evidence supports a hypothesis are objective rather than depending on subjective factors like one’s own language or epistemic values. Objectivism about evidential support is key to defending a synchronic, time-slice-centric conception of epistemic rationality, on which what you ought to believe at a time depends only on what evidence you have at that time, and not on how you were at previous times. Here, I defend a version of objectivism about evidential support on which facts about evidential support are grounded in facts about explanatoriness.

I advocate Time-Slice Rationality, the thesis that the relationship between two time-slices of the same person is not importantly different, for purposes of rational evaluation, from the relationship between time-slices of distinct persons. The locus of rationality, so to speak, is the time-slice rather than the temporally extended agent. This claim is motivated by consideration of puzzle cases for personal identity over time and by a very moderate form of internalism about rationality. Time-Slice Rationality conflicts with two proposed principles of rationality, Conditionalization and Reflection. Conditionalization is a diachronic norm saying how your current degrees of belief should fit with your old ones, while Reflection is a norm enjoining you to defer to the degrees of belief that you expect to have in the future. But they are independently problematic and should be replaced by improved, time-slice-centric principles. Conditionalization should be replaced by a synchronic norm saying what degrees of belief you ought to have given your current evidence and Reflection should be replaced by a norm which instructs you to defer to the degrees of belief of agents you take to be experts. These replacement principles do all the work that the old principles were supposed to do while avoiding their problems. In this way, Time-Slice Rationality puts the theory of rationality on firmer foundations and yields better norms than alternative, non-time-slice-centric approaches.

Reasons without Persons is a defense of a time-slice-centric conception of rationality, on which the locus of rationality, to speak metaphorically, is the time-slice rather than the temporally extended person. On this view, the relationship between two time-slices of a single agent (your earlier self and your later self, say) is not different in kind, as far as rational evaluation is concerned, from the relationship between two distinct agents. How you are, or how you believe you are, at other times plays no special role in determining what rationality requires of you right now.

Determing what you ought to do can be broken down into two stages. The first stage is determining what your options are, and the second stage is ranking those options. While the second stage has been widely explored by philosophers of all stripes, from ethicists to decision theorists to epistemologists to action theorists, the first stage has gone largely unaddressed. And yet, without a theory of how to conceive of your options, the theory of practical rationality of how you ought to act will be incomplete. I will argue that the fact that what you ought to do depends on your uncertainty about the world ultimately forces us to conceive of your options as consisting of all and only the decisions you are presently able to make. In this way, oughts apply only to decisions, and not to the non-mental acts that we ordinarily evaluate for moral and rational permissibility. This change in our conception of your options is not of mere bookkeeping interest; it has substantive implications for first-order normative theorizing. First, it directly takes into account the potential costs and benefits of the decision itself in determining what you ought to do. Second, it provides a principled solution to Chisholm’s Paradox, in which your doubts about your own self-control seem to give rise to conflicting claims