My main research falls under several overlapping categories in the metaphysics of causation:
1. Redundant Causation. According to prevailing metaphysical theories of minds and objects, our world is causally crowded: every effect has multiple sufficient causes. Redundant causation plays a central role in numerous debates, from mental causation to the existence of ordinary objects to counterfactual analyses of causation. I carefully examine redundant causation-- its varieties, and its conditions for occurrence-- and show the implications for the metaphysics of causation, mental causation, moral responsibility, and free will.
Overdetermination Underdetermined (under review) [abstract]
Frequently, widespread causal overdetermination is levied as an objection to various metaphysical views. I mount a detailed investigation of causal overdetermination: its various species, denials of it, and objections to it. First, I taxonomize causal overdetermination based on four axes of difference: distinctness of causes, occurrence of causes, causal sufficiency, and nature of the effect. Second, I argue that several attempts to deny causal overdetermination fail. Third, I use the taxonomy to separate out problematic from non-problematic kinds of overdetermination. Finally, I suggest that overdetermination is a red herring for debates about the causal efficacy of minds and objects.
Trumping and Causal Connection (under review) [abstract]
According to Schaffer (2000a), "trumping preemption" is a category of redundant causation distinct from early and late preemption and from overdetermination. Schaffer holds that trumping isn't a case of late preemption because both causal processes "run to completion," and trumping isn't overdetermination because there is only one actual cause. I outline several different kinds of causal completion, and show how Schaffer's argument depends on an ambiguity between two types of causal completion. I then argue that the putative causal asymmetry between causal processes in cases thought to be trumping preemption generates early preemption or overdetermination rather than trumping. This conclusion reveals important lessons about the relationship between causation and laws.
Actual and Counterfactual Redundancy [abstract]
Traditionally, causal overdetermination is taken to involve multiple causes whose actual causal contributions are sufficient to bring about an effect. For example: Billy and Suzy each throw a rock through a window, and the actual impact of each rock is individually sufficient to shatter the window.
But certain special cases of redundant causation defy easy categorization due to this presumption. In Yablo's 'smart rock' case, Billy has a normal rock while Suzy has a satellite-guided rock poised to shatter the window if Billy's rock doesn't. Either is sufficient to shatter the window, but only one rock is intuitively the cause. In Schaffer's 'trumping preemption,' two magicians cast spells, each of which is sufficient to bring about an effect, but only one of which is intuitively the cause. In Sartorio's 'colliding bullets' case, two bullets are discharged with speed sufficient to kill Victim, but collide midstream such that their combined force is necessary to bring about Victim's death.
Rather than viewing these cases as preemption or joint causation, I argue that we should view them as special sorts of overdetermination-- overdetermination involving counterfactual, rather than actual, causal sufficiency of one cause. An event g1 in a class of causes C counterfactually overdetermines an effect e if had other causes g2, g3, g4, etc. not occurred, g1 would have brought about e in precisely the way that it happened. I develop this new notion of counterfactual overdetermination and show how it accounts for several controversial cases of redundant causation. I then suggest that there is theoretical pressure to consider merely possible causes as causes simpliciter.
It is clear that the questions of how to understand free will and mental causation are deeply connected, for events of seemingly free choosing are mental events that appear capable of causing other mental and physical events (e.g., intentions to pet the cat, cat-pettings). It is thus surprising that the free will and mental causation debates have proceeded largely independently of each other.
Here we aim to make progress in exploring their connections. We show that the problems of free will and of mental causation are special cases of a more general problem, concerning whether and how mental events of a given type may be causally efficacious, given their apparent causal irrelevancy for effects of the type in question. We also identify parallels between certain of the standard responses to the two problems: we argue that hard determinism is parallel to eliminativist physicalism; and we use this parallel to identify an objection to hard determinism that is better than one common objection to this position.
We next argue that compatibilism is parallel to non-reductive physicalism; here our primary aim is to elucidate the deep structural similarity between the strategies underlying these accounts, which similarity supports compatibilism's viability as a principled intermediate position between hard determinism and libertarianism.
2. Causation by Omission. Omissions are metaphysically puzzling. On the one hand, they seem to be nothing: they are events that do not occur. On the other hand, we intuitively reify omissions, grant them causal efficacy, and hold agents morally responsible for their outcomes. I defend a positive view of omissions that resolves ontological, causal, moral, and semantic puzzles about omissions, and show how the metaphysics of omissions intersects with deeper questions about negative properties and non-being.
Omissions as Possibilities (forthcoming in Philosophical Studies) [abstract]
I present and develop the view that omissions are de re modal possibilities of actual events. Omissions do not literally fail to occur; rather, they possibly occur. An omission is a tripartite metaphysical entity composed of an actual event, a possible event, and a contextually specified counterpart relation between them.
I use the view to make new inroads in understanding the role of omissions in causation and in moral responsibility. In particular, I show how the view gives us a new grasp on Peter Singer's argument for giving to charity, in which failing to give to charity is likened to failing to save a drowning child. I use my view to show why Singer's argument is resistant to lines of argumentation that attempt to show differences between the child?s drowning and the failing to give to charity: both omissions have metaphysical parity.
Tangled Up in Blue (under review) [abstract]
The problem of profligate omissions is as follows: Suppose that the gardener promises to water your plant while you are out of town, the gardener fails to water it, and the plant dies. Intuitively, the gardener’s failing to water the plant is a cause of the plant’s death. But the Queen of England also failed to water the plant, and the counterfactual “Had the Queen of England not failed to water the plant, the plant would not have died” is true. Thus a simple counterfactual test would lead us to classify the Queen of England’s omission as a cause of the plant’s death. How can we metaphysically distinguish the relevant omission or omissions from the irrelevant ones?
One attempt to solve the problem of profligate omissions utilizes proportionality. Proportionality selects a single determinate of a determinable-- the determinate proportional to the effect-- as the exclusive cause of an effect.
But this strategy cannot be successful unless the determinate/ determinable distinction can be applied sensibly to the types of properties at stake in omissive causal claims: negative properties. I show that the determinate/ determinable relationship that holds between properties like blue and aqua does not hold between negative properties like not blue and not aqua. The inapplicability of the determinate/ determinable distinction to negative properties blocks the proportionality strategy to the problem of profligate omissions.
3. Causation and Moral Responsibility. Causation and moral responsibility are tightly connected. But certain types of "weird causation"-- overdetermination, joint causation, causal preemption, and causation by omission-- show this relationship to be more complicated than mere necessity or sufficiency. Investigating cases of redundant causation reveals hidden features of our moral evaluative judgments and the limitations of leading theories of causation in modeling these judgments.
Moral Overdetermination [abstract]
I define moral overdetermination as a case where two or more entities are equally morally responsible for an entire outcome. I examine what moral overdetermination demonstrates about the relationship between causation and moral responsibility, and draw several conclusions.
First, attributions of moral responsibility in cases of overdetermination reflect a conflict in counterfactual and productive causal concepts.
Second, current theories of causation do not have the resources to account for differential causal contributions.
Third, causal overdetermination unearths a new kind of moral luck I call proportionality luck, and a correct analysis of responsibility in overdetermination cases is a de facto commitment to its ubiquity.
The Vagueness of Moral Responsibility [abstract]
How close must an agent be to bringing about an outcome to be
held morally responsible for that outcome? For example: suppose that an assassin shoots
and kills a victim at noon. And suppose that a lazy assassin arrives on the scene three
hours later, assumes that Victim is merely sleeping, and shoots Victim himself.
Intuitively, the second assassin isn't morally responsible for the second death, whereas
the first assassin is. But if the second assassin had shot his bullet a mere second after the first, he would have been responsible.
The closeness of the possibility of his bringing about the effect would have made him entirely morally responsible. And yet there is no sharp cutoff for when a possible cause is taken to be an actual cause. I call this idea the vagueness of moral responsibility, and it has far-reaching consequences for topics in both causation and ethics.
4. Causation and Time Travel. If time and causation share an intrinsic direction, what does time travel imply about causation? I examine the relationship between time and causation given reversals of direction in both.
Nowhere Man: Time Travel and Spatial Location (commissioned for Time Travel, Oxford University Press, ed. Richard Hanley) [abstract]
I examine two questions about spatial location with respect to time travel: assuming that time travel takes time, (i) where are objects, events, and people spatially located for the duration of travel through time? and (ii) exactly what are the spatial relata that are transported through time? I argue that all answers to (i) generate either paradoxes of self-annihilation or problematic metaphysical commitments, and show the conseqences of this for (ii).
Three Conceptions of Time Travel (commissioned for Festschrift for Peter van Inwagen) [abstract]
In "Changing the Past" (2010), Peter van Inwagen argues that a time traveler can change the past without paradox in a growing block universe. By erasing the part of the block in the past that generates paradox, a new, non-paradox-generating block can be ?grown? after the temporal relocation of the time traveler and her changes.
I articulate and distinguish between three different conceptions of time travel: (i) time travel in which in which the location of the objective present is shifted by the time traveler, (ii) time travel in which there is a split between the objective present and the subjective present of the time traveler, and (iii) time travel in a universe in which there is no objective present. I then deepen understanding of van Inwagen?s view by filling in its details and showing how it occupies a middle ground between these three types of time travel.
(Please email me at sara dot bernstein at duke dot edu if you would like a copy of any draft.)