This paper provides several examples of how modal logic can be used in studying the XML document navigation language XPath. More specifically, we derive complete axiomatizations, computational complexity and expressive power results for XPath fragments from known results for corresponding logics. A secondary aim of the paper is to introduce XPath in a way that makes it accessible to an audience of modal logicians.

This paper provides several examples of how modal logic can be used in studying the XML document navigation language XPath. More specifically, we derive complete axiomatizations, computational complexity and expressive power results for XPath fragments from known results for corresponding logics. A secondary aim of the paper is to introduce XPath in a way that makes it accessible to an audience of modal logicians.

The possibility question concerns the status of possibilities: do they form an irreducible category of the external reality, or are they merely features of our cognitive framework? If fundamental physics is ever to shed light on this issue, it must be done by some future theory that unifies insights of general relativity and quantum mechanics. The paper investigates one programme of this kind, namely the causal sets programme, as it apparently considers alternative developments of a given system. To evaluate this (...) claim, we prove some algebraic facts about the sequential growth of causal sets. These facts tell against alternative developments, given that causal sets are understood as particular events. We thus interpret causal sets as multi-realisable objects, like states. This interpretation, however, is undermined by an argument for the probabilistic constraint of general covariance, as it says that multiple paths along which a causal set is produced are not physically different. (shrink)

The article is an outline of some of the key thoughts of two Dutch Calvinist philosophers who have had a major impact on sections of modern evangelicalism. These key thoughts are sphere sovereignty, closely associated with Kuyper but adopted enthusiastically by Dooyeweerd as well, and modal aspects, which is particularly associated with Dooyeweerd. The impact of these key thoughts on how we should view social structures is given, focusing particularly on the state, the church, the family and marriage, (...) and the university. There is one key reservation about this line of thinking, held because so prevalent among in the Neo-Calvinist circles so inspired by Kuyper and Dooyeweerd, that of pillarisation. It is argued briefly here, effectively as a postscript, that this represents a line of thinking that does not belong to sphere sovereignty or to modal aspects. (shrink)

This paper discusses some of the modal involvements of analytical mechanics. I first review the elementary aspects of the Lagrangian, Hamiltonian and Hamilton-Jacobi approaches. I then discuss two modal involvements; both are related to David Lewis' work on modality, especially on counterfactuals. The first is the way Hamilton-Jacobi theory uses ensembles, i.e. sets of possible initial conditions. The structure of this set of ensembles remains to be explored by philosophers. The second is the way the Lagrangian and (...) Hamiltonian approaches' variational principles state the law of motion by mentioning contralegal dynamical evolutions. This threatens to contravene the principle that any actual truth, in particular an actual law, is made true by actual facts. Though this threat can be avoided, at least for simple mechanical systems, it repays scrutiny; not least because it leads to some open questions. (shrink)

This paper discusses the interaction of aspect and modality, and focuses on the puzzling implicative effect that arises when perfective aspect appears on certain modals: perfective somehow seems to force the proposition expressed by the complement of the modal to hold in the actual world, and not merely in some possible world. I show that this puzzling behavior, originally discussed in Bhatt (1999, Covert modality in non-finite contexts) for the ability modal, extends to all modal auxiliaries with (...) a circumstantial modal base (i.e., root modals ), while epistemic interpretations of the same modals are immune to the effect. I propose that implicative readings are contingent on the relative position of the modal w.r.t. aspect: when aspect scopes over the modal (as I argue is the case for root modals), it forces an actual event, thereby yielding an implicative reading. When a modal element scopes over aspect, no actual event is forced. This happens (i) with epistemics, which structurally appear above tense and aspect; (ii) with imperfective on a root modal: imperfective brings in an additional layer of modality, itself responsible for removing the necessity for an actual event. This proposal enables us to solve the puzzle while maintaining a standardized semantics for aspects and modals. (shrink)

This work analyses the speech-act of arguing as proposed by Linguistic Normative Model of Argumentation (LNMA) with the help of diagrams, examples and basic formalization techniques. The focus is set on one of the most novel issues of LNMA, modal qualification, and the distinction between epistemic and ontological modals. The first conclusion is that employing LNMA in order to analyse and evaluate actual argumentation as it is proposed is too complex to be applied as is. The second conclusion, at (...) a theoretical level, is that the distinction between ontological and epistemic modals is highly problematic in LNMA. (shrink)

I draw together some recent literature on the debate between dynamical versus geometrical approaches to spacetime theories, in order to argue that there exist defensible versions of the geometr...

Weakly Aggregative Modal Logic ) is a collection of disguised polyadic modal logics with n-ary modalities whose arguments are all the same. \ has interesting applications on epistemic logic, deontic logic, and the logic of belief. In this paper, we study some basic model theoretical aspects of \. Specifically, we first give a van Benthem–Rosen characterization theorem of \ based on an intuitive notion of bisimulation. Then, in contrast to many well known normal or non-normal modal (...) logics, we show that each basic \ system \ lacks Craig interpolation. Finally, by model theoretical techniques, we show that an extension of \ does have Craig interpolation, as an example of amending the interpolation problem of \. (shrink)

Anti-materialist thought experiments as, e.g., zombie arguments, have posed some of the most vexing problems for materialist accounts of phenomenal consciousness. I doubt, however, that arguments of this kind can refute the core thesis of materialism. Although I do not question that there is something very special about an adequate explanation of phenomenal consciousness, and although I accept the epistemic irreducibility of phenomenal consciousness, I deny that modal arguments reach far enough to establish essentialism about consciousness. I will draw (...) upon a relativistic conception of modal space and suggest to strictly separate between varieties of metaphysical possibility - depending on which world is considered as actual, and depending on accessibility relations. It is shown that the modal argument cannot endanger the reductive explanation of the mind-brain relation if one distinguishes carefully between possibility according to primary intensions and possibility according to secondary intensions . Modal arguments are strong enough to make an epistemological point but not an ontological one. (shrink)

Many of the formalisms used in Attribute Value grammar are notational variants of languages of propositional modal logic, and testing whether two Attribute Value Structures unify amounts to testing for modal satisfiability. In this paper we put this observation to work. We study the complexity of the satisfiability problem for nine modal languages which mirror different aspects of AVS description formalisms, including the ability to express re-entrancy, the ability to express generalisations, and the ability to express (...) recursive constraints. Two main techniques are used: either Kripke models with desirable properties are constructed, or modalities are used to simulate fragments of Propositional Dynamic Logic. Further possibilities for the application of modal logic in computational linguistics are noted. (shrink)

The importance of learning and categorizing social objects and events has become widely acknowledged over a couple of decades. Although findings from field studies have suggested that non-human animals have sophisticated abilities to recognize social objects, there is relatively little experimental evidence on this issue. Some studies have revealed animals’ excellent skills for discriminating visual and auditory social stimuli. However, because of perceptual resemblances among stimuli, it is still not clear that they recognize these objects with conceptual mechanisms that are (...) independent of the perceptual characteristics of the stimuli. At the same time, whether their concepts have an aspect of transferring information from one modality to another has not received much attention. This paper advocates approaches to a cross-modal aspect of concepts as a new framework to solve these problems, and introduces the latest studies on cross-modal representations of social objects in non-humans. (shrink)

In the article I undertake the question of the Ockham’s razor. I consider the basic version of this methodological postulate: entia non sunt multiplicanda praeter necessitatem. I propose to interpret this postulate as a criterion of non-existence. In this context I analyse the matter of accidental entities as well as the ontological principle of economy.

The Brock-Rosen problem has been one of the most thoroughly discussed objections to the modal fictionalism bruited in Gideon Rosen’s ‘Modal Fictionalism’. But there is a more fundamental problem with modal fictionalism, at least as it is normally explained: the position does not resolve the tension that motivated it. I argue that if we pay attention to a neglected aspect of modal fictionalism, we will see how to resolve this tension—and we will also find a persuasive (...) reply to the Brock-Rosen objection. Finally, I discuss an alternative reading of Rosen, and argue that this position is also able to fend off the Brock-Rosen objection. (shrink)

Objective: Evidence suggests people experience an oral size illusion and commonly perceive oral size inaccurately; however, the nature of the illusion remains unclear. The objectives of the present study were to confirm the presence of an oral size illusion, determine the magnitude (amount) and direction (underestimation or overestimation) of the illusion, and determine whether immediately prior crossmodal perceptual experiences affected the magnitude and direction. Design: Participants (N = 27) orally assessed 9 sizes of stainless steel spheres (1/16 in to 1/2 (...) in) categorized as small, medium, or big, and matched them with digital and visual reference sets. Each participant completed 20 matching tasks in 3 assessments. For control assessments, 6 oral spheres were matched with reference sets of same-sized spheres. For primer-control assessments, similar to control, 6 matching tasks were preceded by cross-modal experiences of the same-sized sphere. For experimental assessments, 8 matching tasks were preceded by a cross-modal experience of a differently sized sphere. Results: For control assessments, small and medium spheres were consistently underestimated, and big spheres were consistently overestimated. For experimental assessments, magnitude and direction of the oral size illusion varied according to the size of the sphere used in the cross-modal experience. Conclusion: Results seemed to confirm an oral size illusion, but direction of the illusion depended on the size of the object. Immediately prior cross-modal experiences influenced magnitude and direction of the illusion, suggesting that aspects of oral perceptual experience are dependent upon factors outside of oral perceptual anatomy and the properties of the oral stimulus. (shrink)

The present monograph is a slightly revised version of my Habilitations schrift Proof-theoretic Aspects of Intensional and Non-Classical Logics, successfully defended at Leipzig University, November 1997. It collects work on proof systems for modal and constructive logics I have done over the last few years. The main concern is display logic, a certain refinement of Gentzen's sequent calculus developed by Nuel D. Belnap. This book is far from offering a comprehensive presentation of generalized sequent systems for modal (...) logics broadly conceived. The proof-theory of non-classical logics is a rapidly developing field, and even the generalizations of the ordinary notion of sequent listed in Chapter 1 can hardly be presented in great detail within a single volume. In addition to further investigating the various approaches toward generalized Gentzen systems, it is important to compare them and to discuss their relative advantages and disadvantages. An initial attempt at bringing together work on different kinds of proof systems for modal logics has been made in [188]. Another step in the same direction is [196]. Since Chapter 1 contains introductory considerations and, moreover, every remaining chapter begins with some surveying or summarizing remarks, in this preface I shall only emphasize a relation to philosophy that is important to me, register the sources of papers that have entered this book in some form or another, and acknowledge advice and support. (shrink)

Modal logic is the logic of necessity and possibility, of ‘must be’ and ‘may be’. These may be interpreted in various ways. If necessity is necessary truth, there is alethic modal logic; if it is moral or normative necessity, there is deontic logic [see chapter 8]. It may refer to what is known or believed to be true, in which case, there is an epistemic logic [chapter 9], or to what always has been or to what henceforth always (...) will be true, which gives an aspect of temporal logic [chapter 10]. Another interpretation is to read ‘Necessarily p′ as ‘it is provable that p′ This chapter will present the general framework of modal logic applicable to all of these, though with emphasis on alethic modal logics. (shrink)

A number of philosophical projects require a proper understanding of the modal aspects of agency, or of what I call ‘the agentive modalities.’ I propose a general account of the agentive modalities, one which takes as its primitive the decision-theoretic notion of an option. I relate this account to the standard semantics for ‘can’ and to the viability of some positions in the free will debates.

This book shows that the semantic analysis of modal notions of possibility and necessity can be used to enhance our understanding of the interpretation of reports of belief or emotional state. It introduces intuitive notation and terminology to express ideas in modern theories of modal interpretation that are normally represented in complex logical formulas, effectively updates the 1960s-era link between possible worlds and the semantics of propositional attitude ascriptions, and reconciles two disparate views of the role of events (...) in semantic interpretation, that of Donald Davidson and that of David Lewis. It reduces a host of variable behaviors of propositional attitude ascription to an intuitive and precise distinction between ascriptions that merely express a commitment to propositional content versus ones that attribute a mental state to the holder of the propositional attitude. This leads to an explanation of the nature and effects of the language disorder of fluent aphasia. (shrink)

There is a common assumption in the semantics of modal auxiliaries in natural language; in utterances of MOD φ , where MOD is a modal and φ is the prejacent, context determines the particular flavor of modality expressed by the modal. Such is the standard contextualist semantics of Kratzer and related proposals. This winds up being a problem, because there is a significant class of modals which have constraints on the admissible modal flavor that are not (...) traceable to context. For example, in MUST φ , subsentential properties of φ, like the aspectual class of the predicate in the prejacent, can affect the flavor of MUST. By encoding the above assumption into the semantics, such contextualist accounts fail to be able to explain, much less to predict, this pattern. Worse yet, attempts to exploit the resources of the theory in service of an explanation run afoul of important commitments of the view, like the hypothesis that modals have a uniform semantics. Given these circumstances, these data might seem like a justification for dispensing with the uniformity hypothesis. The present paper lays out the above problem in detail. Against the pessimistic view, I argue that the the contextualist account can in fact explain and predict these patterns while preserving the uniformity hypothesis. This requires adopting an amendment to the semantics of modals based on the work of Valentine Hacquard. Aside from maintaining the contextualist paradigm and preserving uniformity, the proposal also clarifies the role of context in the interpretation of modals. As it will turn out, the role of context ought to be circumscribed in its flavor-determining role for modals. (shrink)

We investigate the dynamics of sensory integration for perceiving musical performance, a complex natural behavior. Thirty musically trained participants saw, heard, or both saw and heard, performances by two clarinetists. All participants used a sliding potentiometer to make continuous judgments of tension (a measure correlated with emotional response) and continuous judgments of phrasing (a measure correlated with perceived musical structure) as performances were presented. The data analysis sought to reveal relations between the sensory modalities (vision and audition) and to quantify (...) the effect of seeing the performances on participants' overall subjective experience of the music. In addition to traditional statistics, functional data analysis techniques were employed to analyze time-varying aspects of the data. The auditory and visual channels were found to convey similar experiences of phrasing but different experiences of tension through much of the performances. We found that visual information served both to augment and to reduce the experience of tension at different points in the musical piece (as revealed by functional linear modeling and functional significance testing). In addition, the musicians' movements served to extend the sense of phrasing, to cue the beginning of new phrases, to indicate musical interpretation, and to anticipate changes in emotional content. Evidence for an interaction effect suggests that there may exist an emergent quality when musical performances are both seen and heard. The investigation augments knowledge of human communicative processes spanning language and music, and involving multiple modalities of emotion and information transfer. (shrink)

I present a case for a rapprochement between aspects of rationalism and scientific realism, by way of a general framework employing modal epistemology and elements of 2-dimensional semantics (2DS). My overall argument strategy is meta-inductive: The bulk of this paper establishes a “base case,” i.e., a concretely constructive example by which I demonstrate this linkage. The base case or constructive example acts as the exemplar for generating, in a constructively ‘bottom-up’ fashion, a more generally rigorous case for rationalism-realism (...) qua modal epistemology. The exemple I choose in D. Chalmers’ (2002) modal rationalism and R. Giere’s (1985, 1988) constructive realism. I show by way of a thorough analysis how Giere’s claims concerning modal scope are characterized as instances of Chalmers’ modal rationalism, both weak and strong. In essence, as I demonstrate via Chalmers’ notions, ceteris paribus the constructive realist ultimately opts for a comparatively wider gate, characterized by modal reasoning, to lead from the rooms of conceivability qua thought experiments and models, to the pastures of metaphysical possibility. Chalmers likewise tries to erect such a wider gate, in his general conceivability-possibility theses. Anti-realists, on the other hand, see a narrower passage and my contention herein is that they suffer from modal myopia, which hopefully the ‘corrective vision’ of Chalmers’ modal rationalism can restore. In the introduction and concluding sections I sketch out suggestions of constructing ‘inductive steps’ from my base case, to generate more extensively general claims regarding realism qua rationalism. -/- . (shrink)

In this paper, I attempt to explain one of the most controversial views attributed to the Stoic Chrysippus: that the impossible can follow from the possible. My solution finds in Chrysippus a distinction later made by the medieval logician John Buridan: that between being possible (there being a state of affairs that may occur) and being possibly-true (there being some proposition whose truth-conditions are that state of affairs). Buridan and Chrysippus have radically opposing views on the nature of propositions. What (...) their conceptions share is the conclusion that at least some propositions must be contingent beings. They argue for this while maintaining a rigorous commitment to the view that propositions are strictly bivalent. In 2. I explain the Chrysippean passage in terms of a distinction Buridan makes explicitly. In 3. I show how the distinction follows implicitly from the Stoic theory of quantification. In 4. I compare the modality with other aspects of Stoic logic. In 5. I discuss how the distinction behaves in the future tense. (shrink)

In this investigation we explore a general strategy for constructing modal theories where the modal notion is conceived as a predicate. The idea of this strategy is to develop modal theories over axiomatic theories of truth. In this first paper of our two part investigation we develop the general strategy and then apply it to the axiomatic theory of truth Friedman-Sheard. We thereby obtain the theory Modal Friedman-Sheard. The theory Modal Friedman-Sheard is then discussed from (...) three different perspectives. First, we show that Modal Friedman-Sheard preserves theoremhood modulo translation with respect to modal operator logic. Second, we turn to semantic aspects and develop a modal semantics for the newly developed theory. Third, we investigate whether the modal predicate of Modal Friedman-Sheard can be understood along the lines of a proposal of Kripke, namely as a truth predicate modified by a modal operator. (shrink)

A series of recent studies have explored the impact of people's judgments regarding physical law, morality, and probability. Surprisingly, such studies indicate that these three apparently unrelated types of judgments often have precisely the same impact. We argue that these findings provide evidence for a more general hypothesis about the kind of cognition people use to think about possibilities. Specifically, we suggest that this aspect of people's cognition is best understood using an idea developed within work in the formal semantics (...) tradition, namely the notion of modality. On the view we propose, people may have separate representations for physical, moral and probabilistic considerations, but they also integrate these various considerations into a unified representation of modality. (shrink)

In §1 I explain that my rejection of possible states of affairs as a basis for an account of falsity is not part of a general rejection of modal notions but is a rejection of possible and impossible entities of any sort. I then show that my account of senses and of propositions is indeed a modal account. In §2 I examine some of Wittgenstein’s ideas about falsity, as presented by Luiz Carlos, in relation to my account of (...) falsity and negation. In §3 I discuss the modal aspects of identification for propositions. (shrink)

‘Modal aspect’ is a central notion in so-called ‘Calvinistic Philosophy’. To be sure, this is true of only one of its versions, namely Dooyeweerd’s. For Vollenhoven’s systematic philosophy, which of course may also lay claim on the title CP, has no use for it. In his version pride of place is given to the notion of ‘function’. This paper is a meditation on the question what ‘aspects’ and ‘functions’, within the bounds of CP, are supposed to be. Doing (...) so will shed, I hope, at least some light on the question which, if any, of the two is the more intelligible and useful notion. Right at the beginning I should like to make it clear that this paper is narrowly focussed on the indicated questions. My aim is not to discuss any theory about modal aspects, such as Dooyeweerd’s theory that modal aspects are refractions in time of something supra temporal, or his theory that there is an Archimedian Point from which human beings can overlook the various modal aspects. Nor will I discuss any theory about functions. The indicated questions seek to establish what the phenomena are that such theories are about. This paper is also narrowly focussed in that whatever differences may turn out to exist in the course of this meditation between Vollenhoven and Dooyeweerd, it will not discuss them in any depth. A serious discussion of these differences will have to take into account the theories that I propose presently not to deal with. Let me now turn to the first question. (shrink)

Counterfactual reasoning has been used to account for many aspects of scientific reasoning. More recently, it has also been used to account for the scientific practice of modeling. Truth in a model is truth in a situation considered as counterfactual. When we reason with models, we reason with counterfactuals. Focusing on selected models like Bohr’s atom model or models of population dynamics, I present an account of how the imaginative development of a counterfactual supposition leads us from reality to (...) interesting model assumptions; how it guides our reasoning from these assumptions to interesting consequences for the model scenario via counterfactual entailment; and how it leads us back to conclusions on real target phenomena. (shrink)

We give an equivalent formulation of topological algebras, interpreting S4, as boolean algebras equipped with intuitionistic negation. The intuitionistic substructure—Heyting algebra—of such an algebra can be then seen as an “epistemic subuniverse”, and modalities arise from the interaction between the intuitionistic and classical negations or, we might perhaps say, between the epistemic and the ontological aspects: they are not relations between arbitrary alternatives but between intuitionistic substructures and one common world governed by the classical (propositional) logic. As an example (...) of the generality of the obtained view, we apply it also to S5. We give a sound, complete and decidable sequent calculus, extending a classical system with the rules for handling the intuitionistic negation, in which one can prove all classical, intuitionistic and S4 valid sequents. (shrink)

I expand modal normativism, a theory of metaphysical modality, to give a normativist account of metaphysical explanation. According to modal normativism, basic modal claims do not have a descriptive function, but instead have the normative function of enabling language users to express semantic rules that govern the use of ordinary non-modal vocabulary. However, a worry for modal normativism is that it doesn’t keep up with all of the important and interesting metaphysics we can do by (...) giving and evaluating metaphysical explanations. So, I advance modal normativism by arguing that metaphysical explanations also have a normative rather than descriptive function. In particular, non-causal explanatory claims have formal and semantic properties that make them expressively stricter than basic modal claims and so are better suited to express fine-grained aspects of semantic rules. A major payoff of my normativist account of metaphysical explanations is that it yields a plausible story about how we come to evaluate and know metaphysical explanations—we do this primarily by conceptual analysis. I also respond to a number of objections, including the objection that the epistemic payoffs of my view are not worth the metaphysical costs. (shrink)

A Short Introduction to Modal Logic presents both semantic and syntactic features of the subject and illustrates them by detailed analyses of the three best-known modal systems S5, S4 and T. The book concentrates on the logical aspects of ...

The purpose of the paper is to explore different aspects of the covariance of non-relativistic quantum mechanics. First, doubts are expressed concerning the claim that gauge fields can be 'generated' by way of imposition of gauge covariance of the single-particle wave equation. Then a brief review is given of Galilean covariance in the general case of external fields, and the connection between Galilean boosts and gauge transformations. Under time-dependent translations the geometric phase associated with Schrödinger evolution is non-invariant, and (...) the significance of this result is briefly analysed. The covariance properties of Schrödinger dynamics are then brought to bear on certain versions of the modal interpretation of quantum mechanics. The conclusion that it is only relational properties that can be considered coordinate- or gauge-independent elements of reality is reinforced by appeal to the theory of quantum reference frames due to Aharonov and Kauffher. , Cambridge University Press ; pp. 45-70.). (shrink)

Although the philosophical systems of G. W. Leibniz and David Lewis both feature possible worlds, the ways in which their systems are similar and dissimilar are ultimately surprising. At first glance, Leibniz’s modal metaphysics might strike us as one of the most contemporarily relevant aspects of his system. But I clarify in this paper major interpretive problems that result from understanding Leibniz’s system in terms of contemporary views (like Lewis’s, for instance). Specifically, I argue that Leibniz rejects the (...) inference that if something is possible, it therefore occurs in some possible world. This discussion highlights how Leibniz’s account of individual substance (with his strict notion of identity) constrains his modal theorizing and produces fatalistic threats. I then make an unexpected connection between Leibniz’s and Lewis’s systems by showing that Leibniz’s treatment of fatalism bears similarities to the response Lewis gives to the fatalist when considering the paradoxes of time travel. (shrink)

This is a first course in propositional modal logic, suitable for mathematicians, computer scientists and philosophers. Emphasis is placed on semantic aspects, in the form of labelled transition structures, rather than on proof theory. The book covers all the basic material - propositional languages, semantics and correspondence results, proof systems and completeness results - as well as some topics not usually covered in a modal logic course. It is written from a mathematical standpoint. To help the reader, (...) the material is covered in short chapters, each concentrating on one topic. These are arranged into five parts, each with a common theme. An important feature of the book is the many exercises and an extensive set of solutions is provided. (shrink)

Modality is a category of linguistic meaning having to do with the expression of possibility and necessity. A modalized sentence locates an underlying or prejacent proposition in the space of possibilities. Sandy might be home says that there is a possibility that Sandy is home. Sandy must be home says that in all possibilities, Sandy is home. The counterpart of modality in the temporal domain should be called “temporality”, but it is more common to talk of tense and aspect, the (...) prototypical verbal expressions of temporality. Together, modality and temporality are at the heart of the property of “displacement” that enables natural language to talk about affairs beyond the actual here and now. (shrink)

Differences in the interpretation of would-conditionals with simple (perfective) and perfect antecedent clauses are marked enough to discourage a unified view. However, this paper presents a unified, Lewis–Stalnaker style semantics for the modal in such constructions. Differences in the interpretation of the conditionals are derived from the interaction between the interpretation of different types of aspect and the modal. The paper makes a distinction between perfective and perfect aspect in terms of whether they make reference to or quantify (...) over Lewis-style events. In making reference to Lewis-events, perfective aspect is shown to be incompatible with counterfactual would-conditionals. The so-called ‘epistemic flavor’ of perfective conditionals about the future is derived from the use of diagonalization as an interpretive strategy called upon to resolve reference. (shrink)