I give two arguments for the claim that all events which occur at the actual world and are such that they could be caused, are also such that they must actually be caused. The first argument is an improvement of a similar argument advanced by Alexander Pruss, which I show to be invalid. It uses Pruss’s Brouwer Analog for counterfactual logic, and, as a consequence, implies inconsistency with Lewis’s semantics for counterfactuals. While (I suggest) this consequence may not be objectionable, (...) the argument founders on the fact that Pruss’s Brouwer Analog has a clear counterexample. I thus turn to a second, “Lewisian” argument, which requires only an affirmation of one element of Lewis’s analysis of causation and one other, fairly weak possibility claim about the nature of wholly contingent events. The final section of the paper explains how both arguments escape objections from supposed indeterminacy in quantum physics. (shrink)

Consider the reasonable axioms of subjunctive conditionals if p → q1 and p → q2 at some world, then p → at that world, and if p1 → q and p2 → q at some world, then → q at that world, where p → q is the subjunctive conditional. I show that a Lewis-style semantics for subjunctive conditionals satisfies these axioms if and only if one makes a certain technical assumption about the closeness relation, an assumption that is probably (...) false. I will then show how Lewisian semantics can be modified so as to assure and even when the technical assumption fails, and in fact in one sense the semantics actually becomes simpler then. (shrink)

In this paper, I explore anomalous dualism about consciousness, a view that has not previously been explored in any detail. We can classify theories of consciousness along two dimensions: first, a theory might be physicalist or dualist; second, a theory might endorse any of the three following views regarding causal relations between phenomenal properties (properties that characterize states of our consciousness) and physical properties: nomism (the two kinds of property interact through deterministic laws), acausalism (they do not causally interact), and (...) anomalism (they interact but not through deterministic laws). I suggest that a kind of anomalous dualism, nonreductive anomalous panpsychism, promises to offer the best overall answer to two pressing issues for dualist views, the problem of mental causation and the mapping problem (the problem of predicting mind-body associations). (shrink)

According to a widely held view of the matter, whenever we assess beliefs as ‘rational’ or ‘justified’, we are making normative judgements about those beliefs. In this discussion, I shall simply assume, for the sake of argument, that this view is correct. My goal here is to explore a particular approach to understanding the basic principles that explain which of these normative judgements are true. Specifically, this approach is based on the assumption that all such normative principles are grounded in (...) facts about values, and the normative principles that apply to beliefs in particular are grounded in facts about alethic value––a kind of value that is exemplified by believing what is true and not believing what is false. In this chapter, I shall explain what I regard as the best way of interpreting this approach. In doing so, I shall also show how this interpretation can solve some problems that have recently been raised for approaches of this kind by Selim Berker, Jennifer Carr, Michael Caie, and Hilary Greaves. (shrink)

The epistemic thesis is the thesis that a 'might' counterfactual like 'If Matt had gone to the parade, David might have gone to the parade' has the same meaning as 'Maybe, if Matt had gone to the parade, David would have gone to the parade.' I offer a new theory of the counterfactual interpretation of the modal 'might' on which 'might' has the same meaning as 'maybe would'. And I show that, when coupled with a plausible semantics for 'if' clauses, (...) my theory validates the epistemic thesis. (shrink)

What is the connection between valid inference and true conditionals? Many conditional logics require that when A is a logical consequence of B, "if B then A" is true. Taking counterlogical conditionals seriously leads to systems that permit counterexamples to that general rule. However, this leaves those of us who endorse non-trivial accounts of counterpossible conditionals to explain what the connection between conditionals and consequence is. The explanation of the connection also answers a common line of objection to non-trivial counterpossibles, (...) which is based on a transition from valid arguments to the corresponding conditionals. It also contributes to the wider project of illuminating the connections between contexts of utterance, on the one hand, and the truth-conditions of conditionals uttered in those contexts, on the other. (shrink)

“S ought (not) to see to it that p at t” is true iff an intention on the part of S to see to it that p at t is (in) correct. From this truth condition follows an understanding of the conceptual role of ought-claims in practical inference: ought-claims are interchangeable with intentions having the same content. From this conceptual role, it is quite clear why first-person, present-tense ought-judgments, and just those, motivate: failure to be motivated is a failure of (...) rationality. The point and purpose of 'ought' is mainly to express the results of practical reasoning performed on premises held hypothetically, an exercise of which there are many varieties. Our capacity for normative thought and language is a consequence of, and intimately related to, our capacity for practical thought. (shrink)

The classic formulation of causal decision theory (CDT) appeals to counterfactuals. It says that you should aim to choose an option that would have a good outcome, were you to choose it. However, this version of CDT faces trouble if the laws of nature are deterministic. After all, the standard theory of counterfactuals says that, if the laws are deterministic, then if anything—including the choice you make—were different in the present, either the laws would be violated or the distant past (...) would be changed. And as several authors have shown, it's easy to transform this upshot of the standard theory of counterfactuals into full-blown counterexamples to CDT. In response to these counterexamples, I argue here that the problem lies, not so much with CDT's guiding idea—that it's the expected causal consequences of your actions that matter for rational decision-making—but with the fact that the classic formulation of CDT doesn't pay sufficient attention to the context-sensitivity of counterfactuals. I develop a contextualist version of CDT which better accounts for this context-sensitivity. And I show that my theory avoids the problems faced by the classic formulation of CDT in determinstic worlds. (shrink)

SummaryThis paper develops a semantical account of sentences containing performative principal verbs in which these verbs are analyzed as indexical expressions: the proposition picked out by a sentence containing a performative verb depends on aspects of the context of use of the sentence; and these same aspects of context of use also determine the truth value of the proposition picked out. A two‐dimensional modal operator is utilized in analyzing non‐ performative sentences that contain principal verb which, in other contexts, have (...) performative uses. Thus, the analysis developed accounts for the performative — non‐performative distinction within a formal semantic‐pragmatic framework; the more common approach of relegating the distinction to the somewhat vague realm of ‘language use’ is avoided.RésuméCet article développe un traitement sémantique des phrases contenant un verbe principal performatif. Ces verbes sont analysés comme des expressions indicées: la proposition sélectionnée par une phrase contenant un verbe performatif dépend du contexte d'usage de cette phrase; et ces mêmes aspects du contexte d'usage déterminent également la valeur de vérité de la proposition sélectionnée. Un opérateur modal à deux dimensions est utilisé pour l'analyse de phrases non‐performatives contenant un verbe principal performatif dans d'autres contextes. L'analyse développée rend ainsi compte de la distinction performatif — non‐performatif dans un cadre sémantico‐pragmatique; on évite ainsi la solution habituelle consistant à reléguer cette distinction dans le domaine plutôt vague de l'usage linguistique.ZusammenfassungEs wird eine semantische Darstellung von Sätzen entwickelt, die performative Hauptverben enthalten, indem diese Verben als indexikale Ausdrücke analysiert werden: die Proposition, die durch einen Satz mit einem performativen Verb bezeichnet wird, hängt von Aspekten des Gebrauchskontextes des Satzes ab; und gerade diese Aspekte bestimmen auch den Wahrheitswert der Proposition. Ein zweidimensionaler Modaloperator wird verwendet, um nicht‐performative Sätze zu analysieren, die Hauptverben enthalten, welche — in andern Kontexten — einen performativen Gebrauch haben. Auf diese Weise gibt die entwickelte Analyse innerhalb eines formalen semantisch‐syntaktischen Rahmenwerkes Rechenschaft über die Unterscheidung performativ — nicht‐performativ; man vermeidet dadurch das übliche Vorgehen, die Unterscheidung in den etwas vagen Bereich des sog. 〈Sprachgebrauchs〉 abzuschieben. (shrink)

Provisional draft, pre-production copy of my book “The Modal Future” (forthcoming with Cambridge University Press).

Indicative conditionals and tendency causal claims are closely related (e.g., Frosch and Byrne, 2012), but despite these connections, they are usually studied separately. A unifying framework could consist in their dependence on probabilistic factors such as high conditional probability and statistical relevance (e.g., Adams, 1975; Eells, 1991; Douven, 2008, 2015). This paper presents a comparative empirical study on differences between judgments on tendency causal claims and indicative conditionals, how these judgments are driven by probabilistic factors, and how these factors differ (...) in their predictive power for both causal and conditional claims. (shrink)

This book proposes a semantic theory of conditionals that can account for (i) the variability in usages that conditional sentences can be put; and (ii) both conditional sentences of the form ‘if p, q’ and those conditional thoughts that are expressed without using ‘if’. It presents theoretical arguments as well as empirical evidence from English and other languages in support of the thesis that an adequate study of conditionals has to go beyond an analysis of specific sentence forms or lexical (...) items. The resulting perspective on conditionals is one in which conditionality is located at a higher level than that of the sentence; namely, at the level of thought. The author argues that it is only through adopting such a perspective, and with it, a commitment to context-dependent semantics, that we can successfully represent conditional utterances as they are used and understood by ordinary language users. It will be of interest to students and scholars working on the semantics of conditionals in the fields of linguistics (especially semantics and pragmatics) and philosophy of language. (shrink)

This paper defends the case against (sparse) disjunctive properties by means of four Armstrongian arguments. The first of these is a logical atomist argument from truthmaking, which is, broadly speaking, ‘Armstrongian’ (Armstrong 1997). This argument is strong – although it stands or falls with the relevant notion of truthmaking, as it were. However, three arguments, which are prima facie independent of truthmaking, can be found explicitly early in Armstrong’s middle period. Two of these early arguments face a serious objection put (...) forward forcefully by Louise Antony (2003) and Alan Penczek (1997), respectively. I consider these objections and argue that they fail. Thus, even if the argument from truthmaking is indecisive, disjunctive properties should be rejected. (shrink)

In this paper we focus on theorem proving for conditional logics. First, we give a detailed description of CondLean, a theorem prover for some standard conditional logics. CondLean is a SICStus Prolog implementation of some labeled sequent calculi for conditional logics recently introduced. It is inspired to the so called “lean” methodology, even if it does not fit this style in a rigorous manner. CondLean also comprises a graphical interface written in Java. Furthermore, we introduce a goal-directed proof search mechanism, (...) derived from the above mentioned sequent calculi based on the notion of uniform proofs. Finally, we describe GOALDUCK, a simple SICStus Prolog implementation of the goal-directed calculus mentioned here above. Both the programs CondLean and GOALDUCK, together with their source code, are available for free download at. (shrink)

The book discusses the structure, content, and evaluation of cosmological arguments. The introductory chapter investigates features essential to cosmological arguments. Traditionally, cosmological arguments are distinguished by their appeal to change, causation, contingency or objective becoming in the world. But none of these is in fact essential to the formulation of cosmological arguments. Chapters 1-3 present a critical discussion of traditional Thomistic, Kalam, and Leibnizian cosmological arguments, noting various advantages and disadvantages of these approaches. Chapter 4 offers an entirely new approach (...) to the cosmological argument - the approach of theistic modal realism. The proper explananda of cosmological arguments on this approach is not change, causation, contingency or objective becoming in the world. The proper explananda is the totality of metaphysical reality - all actualia and all possibilia. The result is the most compelling and least objectionable version of the cosmological argument. (shrink)

In this paper, we argue that the popular claim that laws of nature explain their instances creates a philosophical puzzle when it is combined with the widely held requirement that explanations need to be underpinned by ‘wordly’ relations. We argue that a “direct solution” to the puzzle that accounts for both explanatory laws and explanatory realism requires endorsing at least a radical metaphysics. Then, we examine the ramifications of a “skeptical solution”, i.e., dissolving it by giving up at least one (...) of these two claims, and argue that adopting it is more favorable to Humean reductionists than to anti-reductionists about laws of nature. (shrink)

The role of causation and counterfactuals in causal decision theory is vexed and disputed. Recently, Brian Hedden (2023) argues that we should abandon causal decision theory in favour of an alternative: counterfactual decision theory. I argue that, pace Hedden, counterfactual decision theory is not a competitor to, but rather a version of, causal decision theory – the most popular version by far. I provide textual evidence that the founding fathers of causal decision theory (Stalnaker, Gibbard, Harper, Lewis, Skyrms, Sobel, and (...) Joyce) all endorse counterfactual decision theories. I additionally discuss why these theories came to be called ‘causal’, rather than ‘counterfactual’. And I argue that, properly understood, causal decision theory escapes Hedden's objections. (shrink)

We define intuitionistic subatomic natural deduction systems for reasoning with elementary would-counterfactuals and causal since-subordinator sentences. The former kind of sentence is analysed in terms of counterfactual implication, the latter in terms of factual implication. Derivations in these modal proof systems make use of modes of assumptions which are sensitive to the factuality status of the formula that is to be assumed. This status is determined by means of the reference proof system on top of which a modal proof system (...) is defined. The introduction and elimination rules for counterfactual (resp. factual) implication draw on this status. It is shown that derivations in the systems normalize and that normal derivations have the subexpression/subformula property. An intuitionistically acceptable proof-theoretic semantics is formulated in terms of canonical derivations. The systems are applied to so-called counterpossibles and to related constructions. (shrink)

The ontology of decision theory has been subject to considerable debate in the past, and discussion of just how we ought to view decision problems has revealed more than one interesting problem, as well as suggested some novel modifications of classical decision theory. In this paper it will be argued that Bayesian, or evidential, decision-theoretic characterizations of decision situations fail to adequately account for knowledge concerning the causal connections between acts, states, and outcomes in decision situations, and so they are (...) incomplete. Second, it will be argues that when we attempt to incorporate the knowledge of such causal connections into Bayesian decision theory, a substantial technical problem arises for which there is no currently available solution that does not suffer from some damning objection or other. From a broader perspective, this then throws into question the use of decision theory as a model of human or machine planning. (shrink)

The task of Philosophy in Science (PinS) is to use philosophical tools to help solve scientific problems. This article describes how I stumbled into this line of work and then addressed several topics in philosophy of biology—units of selection, cladistic parsimony, robustness and trade-offs in model building, adaptationism, and evidence for common ancestry—often in collaboration with scientists. I conclude by offering advice for would-be PinS practitioners.

Essay review of John Carroll's book, _Laws of Nature_.

By analyzing the meaning of time I argue, without endorsing operationalism, that time is necessarily related to physical systems which can serve as clocks. This leads to a version of relationism about time which entails that there is no time 'before' the universe. Three notions of metaphysical 'time' (associated, respectively, with time as a mathematical concept, substantivalism, and modal relationism) which might support the idea of time 'before' the universe are discussed. I argue that there are no good reasons to (...) believe that metaphysical 'time' can be identified with what we ordinarily call time. I also briefly review and criticize the idea of time 'before' the big bang, associated with some recent speculative models in modern cosmology, and I argue that if the big bang model is a (roughly) correct description of our universe, then the best current answer to the question in the title is that time did have a beginning. (shrink)

There has been considerable debate regarding the relative merits of two theses about moral obligation known as actualism and possibilism. Both theses seek to give expression to the general idea that one ought to do the best one can. According to actualism, one’s obligations turn on what would happen if one chose some course of action, whereas, according to possibilism, they turn on what could happen if one chose some course of action. There are two strands to the debate: the (...) substantive verdicts that the two theses render in particular cases, and the accounts that they yield of the conceptual structure of moral obligation. Possibilism is conceptually appealing, whereas actualism is not, but the latter may seem to render superior substantive verdicts. In this paper, it is argued that, by turning from the objectivist’s emphasis on what is actually best to the prospectivist’s emphasis on what one’s evidence indicates is best, possibilists can provide an account of moral obligation that is both conceptually and substantively attractive. (shrink)

The paper is about the interpretation of opaque verbs like “seek”, “owe”, and “resemble” which allow for unspecific readings of their (indefinite) objects. It is shown that the following two observations create a problem for semantic analysis: (a) The opaque position is upward monotone: “John seeks a unicorn” implies “John seeks an animal”, given that “unicorn” is more specific than “animal”. (b) Indefinite objects of opaque verbs allow for higher-order, or “underspecific”, readings: “Jones is looking for something Smith is looking (...) for” can express that there is something unspecific that both Jones and Smith are looking for. Given (a) and (b), it would seem that the following inference is hard to escape, if the premisses are construed unspecifically and the conclusion is taken on its under- specific reading: Jones is looking for a sweater. Smith is looking for a pen. Smith is looking for something Jones is looking for. (shrink)

Meinertsen has recently put forward three arguments against disjunctive properties: the arguments from truthmaking, commonality, and causation. In this paper, I argue that all three arguments fail. The argument from truthmaking rests on the problematic notion of different types of truthmakers and is therefore itself problematic. The argument from commonality may hold but only at the cost of losing much of the philosophical significance of its conclusion. The argument from causation essentially collapses into the argument from truthmaking and is therefore (...) problematic for the same reason as the latter is. I conclude that Meinertsen has not made a case against disjunctive properties. (shrink)

The safety principle is the view that, roughly, if one knows that p, p could not easily have been false. It is common for safety theorists to relativize safety to belief-formation methods. In this paper, I argue that there is no fixed principle of method-individuation that can stand up to scrutiny. I examine various ways to individuate methods and argue that all of them are subject to serious counterexamples. In the end, I conclude by considering some alternative ways to preserve (...) the insight behind safety without invoking a fixed principle of method-individuation. (shrink)

We examine a formal semantics for counterfactual conditionals due to Judea Pearl, which formalizes the interventionist interpretation of counterfactuals central to the interventionist accounts of causation and explanation. We show that a characteristic principle validated by Pearl’s semantics, known as the principle of reversibility, states a kind of irreversibility: counterfactual dependence (in David Lewis’s sense) between two distinct events is irreversible. Moreover, we show that Pearl’s semantics rules out only mutual counterfactual dependence, not cyclic dependence in general. This, we argue, (...) suggests that Pearl’s logic is either too weak or too strong. (shrink)

In the artificial intelligence literature a promising approach to counterfactual reasoning is to interpret counterfactual conditionals based on causal models. Different logics of such causal counterfactuals have been developed with respect to different classes of causal models. In this paper I characterize the class of causal models that are Lewisian in the sense that they validate the principles in Lewis’s well-known logic of counterfactuals. I then develop a system sound and complete with respect to this class. The resulting logic is (...) the weakest logic of causal counterfactuals that respects Lewis’s principles, sits in between the logic developed by Galles and Pearl and the logic developed by Halpern, and stands to Galles and Pearl’s logic in the same fashion as Lewis’s stands to Stalnaker’s. (shrink)

The idea of fragmentalism has been proposed by Kit Fine as a non-standard view of tense realism. This paper examines a modal version of the view, called modal fragmentalism, which combines genuine realism and realism of modality. Modal fragmentalism has been recently discussed by Iaquinto. But unlike Iaquinto, who primarily focused on possibilities de re, in this paper, we focus on expressions of possibilities de dicto. We argue that the chief idea of modal realism should be that different worlds are (...) distinguished not just in terms of how things are differently with respect to each world, but also in terms of how things could have been differently with respect to each world. This demands a realism-oriented semantics for suppositional contents, and more specifically, for conditionals. By deploying a multidimensional semantics for conditionals, we show that there are good reasons to consider modal fragmentalism as a serious approach in metaphysics, which shares many similarities with the fragmentalism of tense. (shrink)

The foregoing set of theorems forms an effective foundation for the theory of situations and worlds. All twenty-five theorems seem to be basic, reasonable principles that structure the domains of properties, relations, states of affairs, situations, and worlds in true and philosophically interesting ways. They resolve 15 of the 19 choice points defined in Barwise (1989) (see Notes 22, 27, 31, 32, 35, 36, 39, 43, and 45). Moreover, important axioms and principles stipulated by situation theorists are derived (see Notes (...) 33, 37, and 38). This is convincing evidence that the foregoing constitutes a theory of situations. Note that worlds are just a special kind of situation, and that the basic theorems of world theory, which were derived in previous work, can still be derived in this situation-theoretic setting. So there seems to be no fundamental incompatibility between situations and worlds — they may peacably coexist in the foundations of metaphysics. The theory may therefore reconcile two research programs that appeared to be heading off in different directions. And we must remind the reader that the general metaphysical principles underlying our theory were not designed with the application to situation theory in mind. This suggests that the general theory and the underlying distinction have explanatory power, for they seem to relate and systematize apparently unrelated phenomena. (shrink)

In the debate about the nature and identity of possible worlds, philosophers have neglected the parallel questions about the nature and identity of moments of time. These are not questions about the structure of time in general, but rather about the internal structure of each individual time. Times and worlds share the following structural similarities: both are maximal with respect to propositions (at every world and time, either p or p is true, for every p); both are consistent; both are (...) closed (every modal consequence of a proposition true at a world is also true at that world, and every tense-theoretic consequence of a proposition true at a time is also true at that time); just as there is a unique actual world, there is a unique present moment; and just as a proposition is necessarily true iff true at all worlds, a proposition is eternally true iff true at all times. In this paper, I show that a simple extension of my theory of worlds yields a theory of times in which the above structural similarities between the two are consequences. (shrink)

The paper argues against Sosa’s claim that sensitivity cannot be differentially supported over safety as the right requirement for knowledge. Its main contention is that, although all sensitive beliefs that should be counted as knowledge are also safe, some insensitive true beliefs that shouldn’t be counted as knowledge are nevertheless safe.

Lange issues a novel challenge to philosophical accounts of laws of nature. He notes that the laws of nature seem to be themselves governed by laws analogous to the way that the laws govern particular facts. These higher order laws are the meta-laws of nature. He claims that if a philosophical account of laws aims to accurately characterize the laws, it should be able to account for these meta-laws. To generalize this challenge, I introduce the notion of roles played by (...) laws of nature according to a philosophical account, and identify a number of salient roles. I then apply Lange’s challenge to two views: the regularity view and the universals view. I argue that the regularity view may be able to meet the generalized version of Lange’s challenge, and that the universals view is able to meet the challenge. 1 Meta-laws2 Lange’s Challenge3 The Roles Played by Laws and Meta-laws4 Meta-laws and the Regularity View5 Meta-laws and the Universals View6 Summary and Conclusion. (shrink)

Newman’s objection is sometimes taken to be a fatal objection to structural realism (SR). However, ambiguity in the definition of “structure” allows for versions that do not succumb to Newman’s objection. In this paper, I consider some versions of SR that maintain an abstract notion of structure yet avoid Newman’s objection. In particular, I consider versions suggested by Melia and Saatsi. They reject a solution that restricts the domain of the second-order quantifiers, and argue in favor of buttressing the language (...) with intensional operators such as “it is physically necessary that...”. I argue that their favored solution effectively requires the former suggestion that they reject. This argument suggests that a notion of natural properties may be indispensable to SR. (shrink)

Dispositional essentialists argue that physical properties have their causal roles essentially. This is typically taken to mean that physical properties are identical to dispositions. I argue that this is untenable, and that we must instead say that properties bestow dispositions. I explore what it is for a property to have such a role essentially. Dispositional essentialists argue for their view by citing certain epistemological and metaphysical implications, and I appeal to these implications to place desiderata on the concept of essence (...) involved. I argue that the traditional modal theory of essence meets these desiderata, but that the resulting theory wrongly implies that certain dispositions essential to mass are essential to charge, thereby offering a new argument against modal theories of essence. I argue that dispositional essentialism requires a primitive notion of essence, and develop a primitivist theory based on Kit Fine's views. I show that the primitivist theory has all the virtues of the modal alternative, and none of the vices. I develop a novel way of thinking about the relationship between properties, laws and dispositions, and argue that it has distinct advantages over standard dispositional essentialist formulations. (shrink)

This is a study in the meaning of natural language probability operators, sentential operators such as probably and likely. We ask what sort of formal structure is required to model the logic and semantics of these operators. Along the way we investigate their deep connections to indicative conditionals and epistemic modals, probe their scalar structure, observe their sensitivity to contex- tually salient contrasts, and explore some of their scopal idiosyncrasies.

This paper defends a counterexample to Modus Tollens, and uses it to draw some conclusions about the logic and semantics of indicative conditionals and probability operators in natural language. Along the way we investigate some of the interactions of these expressions with 'knows', and we call into question the thesis that all knowledge ascriptions have truth-conditions.

Epistemic modal operators give rise to something very like, but also very unlike, Moore's paradox. I set out the puzzling phenomena, explain why a standard relational semantics for these operators cannot handle them, and recommend an alternative semantics. A pragmatics appropriate to the semantics is developed and interactions between the semantics, the pragmatics, and the definition of consequence are investigated. The semantics is then extended to probability operators. Some problems and prospects for probabilistic representations of content and context are explored.

Modal Dimensionalism is a metaphysical theory about possible worlds that is naturally suggested by the often-noted parallelism between modal logic and tense logic. It says that the universe spreads out not only in spatiotemporal dimensions but also in a modal dimension. It regards worlds as nothing more or less than indices in the modal dimension in the way analogous to the way in which Temporal Dimensionalism regards temporal points and intervals as indices in the temporal dimension. Despite its naturalness and (...) intuitive appeal. Modal Dimensionalism has been largely ignored while the debates between David Lewis and his critics have dominated the discourse on the nature of possible worlds. It is high time that we took Modal Dimensionalism seriously as a viable alternative. (shrink)

We prove some embedding theorems for classical conditional logic, covering 'finitely cumulative' logics, 'preferential' logics and what we call 'semi-monotonic' logics. Technical tools called 'partial frames' and 'frame morphisms' in the context of neighborhood semantics are used in the proof.

We address the question of whether it is possible to operate a time machine by manipulating matter and energy so as to manufacture closed timelike curves. This question has received a great deal of attention in the physics literature, with attempts to prove no- go theorems based on classical general relativity and various hybrid theories serving as steps along the way towards quantum gravity. Despite the effort put into these no-go theorems, there is no widely accepted definition of a time (...) machine. We explain the conundrum that must be faced in providing a satisfactory definition and propose a resolution. Roughly, we require that all extensions of the time machine region contain closed timelike curves; the actions of the time machine operator are then sufficiently "potent" to guarantee that closed timelike curves appear. We then review no-go theorems based on classical general relativity, semi-classical quantum gravity, quantum field theory on curved spacetime, and Euclidean quantum gravity. Our verdict on the question of our title is that no result of sufficient generality to underwrite a confident "yes" has been proven. Our review of the no-go results does, however, highlight several foundational problems at the intersection of general relativity and quantum physics that lend substance to the search for an answer. (shrink)

Laurence BonJour has recently proposed a novel and interesting approach to the problem of induction. He grants that it is contingent, and so not a priori, that our patterns of inductive inference are reliable. Nevertheless, he claims, it is necessary and a priori that those patterns are highly likely to be reliable, and that is enough to ground an a priori justification induction. This paper examines an important defect in BonJour's proposal. Once we make sense of the claim that inductive (...) inference is "necessarily highly likely" to be reliable, we find that it is not knowable a priori after all. (shrink)