Kadri Vihvelin, in "What time travelers cannot do" (Philos Stud 81: 315-330, 1996), argued that "no time traveler can kill the baby who in fact is her younger self, because (V1) "if someone would fail to do something, no matter how hard or how many times she tried, then she cannot do it", and (V2) if a time traveler tried to kill her baby self, she would always fail. Theodore Sider (Philos Stud 110: 115-138, 2002) criticized Vihvelin's argument, and Ira (...) Kiourti (Philos Stud 139: 343-352, 2008) criticized both Vihvelin's argument and Sider's critique. I present a critique of Vihvelin's argument different from both Sider's and Kiourti's critiques: I argue in a novel way that both V1 and V2 are false. Since Vihvelin's argument might be understood as providing a challenge to the possibility of time travel, if my critique succeeds then time travel survives such a challenge unscathed. (shrink)

I believe that this approach leads to a wider problem that brings together elements of linguistics and philosophy in an illuminating way. But the single case study that I provide here, while it may be suggestive, does not go far enough to make a good case for the more general point. This paper is extracted from a larger collection of documents, and is intended to motivate and illustrate the ideas.

Determinism is a claim about the laws of nature: very roughly, it is the claim that everything that happens is determined by antecedent conditions together with the natural laws. Incompatibilism is a philosophical thesis about the relevance of determinism to free will: that the truth of determinism rules out the existence of free will. The incompatibilist believes that if determinism turned out to be true, it would also be true that we don't have, and have never had, free will. The (...) compatibilist denies that determinism has the consequences the incompatibilist thinks it has. According to the compatibilist, the truth of determinism does not preclude the existence of free will. (Even if we learned tomorrow that determinism is true, it might still be true that we have free will.) The philosophical problem of free will and determinism is the problem of understanding, how, if at all, the truth of determinism might be compatible with the truth of our belief that we have free will. That is, it's the problem of deciding who is right: the compatibilist or the incompatibilist. (shrink)

Jack Spencer has recently argued for the striking thesis that, possibly, an agent is able to do the impossible—that is, perform an action that is metaphysically impossible for that person to perform. Spencer bases his argument on (Simple G), a case in which it is impossible for an agent G to perform some action but, according to Spencer, G is still intuitively able to perform that action. I reply that we would have to give up at least four action-theoretical principles (...) if we accept that G is able to do the impossible. We may be best off retaining the principles and thus rejecting Spencer's intuition that G is able to do the impossible. I then consider an argument for the claim that G is able to do the impossible that goes through the Snapshot Principle. I, however, deny that any true variant of the Snapshot Principle shows that G is able to do the impossible. Moreover, the counterexample to the Snapshot Principle that I develop also suggests that G is unable to do the impossible in (Simple G). The most natural explanation for why an agent is unable to perform some action in this counterexample extends to (Simple G). Next, I develop three error theories for why we might initially share Spencer's intuition that G is able to do the impossible in (Simple G). Finally, I consider a couple other "G-cases" of Spencer's and find them all wanting. Perhaps we are unable to do the impossible. (shrink)

This essay proposes a new theory of agentive modals: ability modals and their duals, compulsion modals. After criticizing existing approaches—the existential quantificational analysis, the universal quantificational analysis, and the conditional analysis—it presents a new account that builds on both the existential and conditional analyses. On this account, the act conditional analysis, a sentence like ‘John can swim across the river’ says that there is some practically available action that is such that if John tries to do it, he swims across (...) the river. The essay argues that the act conditional analysis avoids the problems faced by existing accounts of agentive modality and shows how the act conditional analysis can be extended to an account of generic agentive modal claims. The upshot is a new vantage point on the role of agentive modal ascriptions in practical discourse: ability ascriptions serve as a kind of hypothetical guarantee, and compulsion ascriptions as a kind of nonhypothetical guarantee. (shrink)

We propose a new analysis of ability modals. After briefly criticizing extant approaches, we turn our attention to the venerable but vexed conditional analysis of ability ascriptions. We give an account that builds on the conditional analysis, but avoids its weaknesses by incorporating a layer of quantification over a contextually supplied set of actions.

The paper presents a logical treatment of actions based on dynamic logic. This approach makes it possible to reflect clearly the differences between static and dynamic elements of the world, a distinction which seems crucial to us for a representation of actions.Starting from propositional dynamic logic a formal system (DLA) is developed, the programs of which are used to model action types. Some special features of this system are: Basic aspects of time are incorporated in DLA as far as they (...) are needed for our purpose. Names for states and for instants are simulated by formulas. It is possible to express formally that a formula is satisfiable or valid. A special program is introduced to reflect developments which are not caused by an official agent but by external influences. (shrink)

This paper is about the principle that success entails ability, which I call Success. I argue the status of Success is highly puzzling: when we focus on past instances of actually successful action, Success is very compelling; but it is in tension with the idea that true ability claims require an action be in the agent's control. I make the above tension precise by considering the logic of ability. I argue Success is appealing because it is classically equivalent to two (...) genuinely valid inferences, which I call Past Success and Can't-Entails-Won't; but also that Success itself has counterexamples. I show how to invalidate Success while validating Past Success and Can't-Entails-Won't by connecting the meaning of ‘can’ to facts about what is settled or open. I define an operator W with features attributed to ‘will’ in the literature on future contingents. I then give a conditional analysis of ability ascriptions stated with W-conditionals, where "S can A" says, roughly, there’s some action available to S such that if S does it, then W(S A). I show this semantics invalidates Success while still explaining its appeal. (shrink)

Accounts of ability in the philosophical literature have tended to be modal ones: claims about an agent’s abilities are understood in terms of what she does in certain non-actual scenarios. In contrast, a prominent account of ability ascriptions in the recent semantics literature appeals to genericity: claims about an agent’s abilities are understood in terms of what she generally manages to do. The latter account resolves some long-standing problems for modal accounts, but encounters problems of its own. I propose a (...) hybrid view, on which ability involves both a modal and a generic element. (shrink)

We introduce and study a PDL-style logic for reasoning about protocols, or plans, under imperfect information. Our paper touches on a number of issues surrounding the relationship between an agent’s abilities, available choices, and information in an interactive situation. The main question we address is under what circumstances can the agent commit to a protocol or plan, and what can she achieve by doing so?

This is part of a larger project that is motivated in part by linguistic considerations and by the philosophical literature in action theory and the logic of ability, but that is also meant to suggest ways in which planning formalisms could be modified to provide an account of the role of ability in planning and practical reasoning.

Philosophers often talk as though each ability is held by exactly one agent. This paper begins by arguing that abilities can be held by groups of agents, where the group is not an agent. I provide a new argument for—and a new analysis of—non-agentive groups’ abilities. I then provide a new argument that, surprisingly, obligations are different: non-agentive groups cannot bear obligations, at least not if those groups are large-scale such as ‘humanity’ or ‘carbon emitters.’ This pair of conclusions is (...) important, since philosophers who endorse large-scale non-agentive groups’ abilities almost universally endorse their obligations. More importantly, the twin arguments (one for abilities, one against obligations) make the following novel contribution: abilities imply agency-involving explanations, while obligations imply action-guidance. This general conclusion should be of interest beyond social ontology. (shrink)

We introduce the logic LRC, designed to describe and reason about agents’ abilities and capabilities in using resources. The proposed framework bridges two—up to now—mutually independent strands of literature: the one on logics of abilities and capabilities, developed within the theory of agency, and the one on logics of resources, motivated by program semantics. The logic LRC is suitable to describe and reason about key aspects of social behaviour in organizations. We prove a number of properties enjoyed by LRC and (...) its associated analytic calculus. These results lay at the intersection of the algebraic theory of unified correspondence and the theory of multitype calculi in structural proof theory. Case studies are discussed which showcase several ways in which this framework can be extended and enriched while retaining its basic properties, so as to model an array of issues, both practically and theoretically relevant, spanning from planning problems to the logical foundations of the theory of organizations. (shrink)

The use of predicate and sentential operators to express the practical modalities -- ability, control, openness, etc. -- has given new life to a fatalistic argument against determinist theories of responsible agency. A familiar version employs the following principle: the consequences of what is unavoidable (beyond one's control) are themselves unavoidable. Accordingly, if determinism is true, whatever happens is the consequence of events in the remote past, or, of such events together with the laws of nature. But laws and the (...) remote past are not under our control and, by the principle, neither are their consequences. Therefore, none of our choices and actions, nor anything that results from them, is under our control.1 Whether refinements of the closure principle underlying this unavoidability argument are acceptable depends upon the precise sense of 'consequence' and 'unavoidable' involved. Roughly, a proposition P is a consequence of a set of propositions M iff it is impossible that P be false when each member of M is true, or, conversely, when M necessitates P. Since P is unavoidable for S when P is true and S is (was) unable to prevent P from being true, it might seem that if P is unavoidable the same should hold of what is necessitated by P. There is, in fact, 1 an easy defense of the principle which utilizes the incompatibilist condition that S is able to do action K only if it is as yet undetermined whether or not S will K. With it, there is no question but that one is unable to accomplish what is already determined by what one was unable to prevent. Of course, this reasoning is unlikely to impress the compatibilist who rejects the condition outright and, expectedly, it is not the procedure of the proponents of the unavoidability argument. The latter might rest content with appeals to intuition, but more significant are defenses of the closure principle and independent derivations of the unavoidability argument that rely upon distinct principles concerning the logic of the practical modalities, for example, closure of ability under entailment (Cross 1986, Brown 1988) or, claims about the "fixity of the past" and the "inescapability of laws" (Ginet 1990).. (shrink)

The problem of luck is advanced and defended against libertarian theories of responsibility-enabling ability. An outline of an account of ability is articulated to explore some features of the sort of ability moral responsibility requires. The account vindicates the luck objection and suggests a novel puzzle: Libertarianism is structurally barred from answering the problem of luck because responsibility requires, but inherently lacks, an explanation from reason states to actions that preserves reliability of connection between responsibility-grounding reasons-sensitivity and action.

Philosophers often talk as though each ability is held by exactly one agent. This paper begins by arguing that abilities can be held by groups of agents, where the group is not an agent. I provide a new argument for—and a new analysis of—non-agentive groups’ abilities. I then provide a new argument that, surprisingly, obligations are different: non-agentive groups cannot bear obligations, at least not if those groups are large-scale such as ‘humanity’ or ‘carbon emitters.’ This pair of conclusions is (...) important, since philosophers who endorse large-scale non-agentive groups’ abilities almost universally endorse their obligations. More importantly, the twin arguments (one for abilities, one against obligations) make the following novel contribution: abilities imply agency-involving explanations, while obligations imply action-guidance. This general conclusion should be of interest beyond social ontology. (shrink)

This paper proposes a formalization of ability that is motivated in part by linguistic considerations and by the philosophical literature in action theory and the logic of ability, but that is also meant to match well with planning formalisms, and so to provide an account of the role of ability in practical reasoning. Some of the philosophical literature concerning ability, and in particular [Austin, 1956], suggests that some ways of talking about ability are context-dependent. I propose a way of formalizing (...) this dependency. (shrink)