A modal theory Z using the Guaspari witness comparison signs $\leq, is developed. The theory Z is similar to, but weaker than, the theory R of Guaspari and Solovay. Nevertheless, Z proves the independence of the Rosser fixed-point. A Kripke semantics for Z is presented and some arithmetical interpretations of Z are investigated. Then Z is enriched to ZI by adding a new modality sign for interpretability and by axioms expressing some facts about interpretability of theories. Two arithmetical interpretations (...) of ZI are presented. The proofs of the validity of the axioms of ZI in arithmetical interpretations use some strengthening of Solovay's result about interpretability in Godel-Bernays set theory. (shrink)

Modal logic has been used to analyze potential infinity and potentialism more generally. However, the standard analysis breaks down in cases of divergent possibilities, where there are two or more possibilities that can be individually realized but which are jointly incompatible. This paper has three aims. First, using the intuitionistic theory of choice sequences, we motivate the need for a modal analysis of divergent potentialism and explain the challenges this involves. Then, using Beth–Kripke semantics for intuitionistic (...) logic, we overcome those challenges. Finally, we apply our modal analysis of divergent potentialism to make choice sequences comprehensible in classical terms. (shrink)

In this article I argue that phenomenal intentionality fundamentally consists in a horizonality structure, rather than in a relation to a representational content or the determination of accuracy conditions. I provide a distinctive modal model of intentionality that conceives of phenomenal intentionality as the enjoyment of a plus ultra that points beyond what is actual. The directedness of intentionality on the world, thus, consists in “pointing ahead” to possibilities. The principal difficulty for the modal model is logical: the (...) most obvious way of implementing such a structure results in an analogue of Russell’s paradox. However, this paradox can be avoided by fine-tuning the modal logic deployed in this setting. This way of fine-tuning the logic ultimately amounts to intuitive benefits. For, it captures the intensional character of intentionality, since the way that our mental states refer to things is conception-dependent. Moreover, the way I interpret the modal model leads to a conception of intentionality as a feature of dynamic, diachronic patterns in the way that mental acts subjectively appear, rather than as a synchronic property. We ought to think of intentionality as fundamentally a temporal, subjective determination. In a generalization on Sellars’ approach to concepts, I hold that phenomenally intentional mental presentations involve modal laws and are inconceivable without them. (shrink)

Computational systems are traditionally approached from control-oriented perspectives; however, as soon as we move from centralized to decentralized computational infrastructures, direct control needs to be replaced by distributed coordination mechanisms that are on par with institutional constructs observable in human societies (contracts, agreements, enforcement mechanisms, etc.). This paper presents a formalization of Hohfeld's framework building upon a logic whose language includes primitive operators of ability and parametric deontic operators. The proposal is meant to highlight the fundamental interaction between deontic and (...) potestative concepts and contains proofs of soundness and completeness with respect to a class of relational models. (shrink)

We offer an analysis of future morphemes as epistemic operators. The main empirical motivation comes from the fact that future morphemes have systematic purely epistemic readings—not only in Greek and Italian, but also in Dutch, German, and English will. The existence of epistemic readings suggests that the future expressions quantify over epistemic, not metaphysical alternatives. We provide a unified analysis for epistemic and predictive readings as epistemic necessity, and the shift between the two is determined compositionally by the (...) lower tense. Our account thus acknowledges a systematic interaction between modality and tense—but the future itself is a pure modal, not a mixed temporal/modal operator. We show that the modal base of the future is nonveridical, i.e. it includes p and ¬p worlds, parallel to epistemic modals such as must, and present arguments that future morphemes are a category that stands in between epistemic modals and predicates of personal taste. We identify, finally, a subclass of epistemic futures which are ratificational, and argue that will is a member of this class. (shrink)

A general method for generating contraction- and cut-free sequent calculi for a large family of normal modal logics is presented. The method covers all modal logics characterized by Kripke frames determined by universal or geometric properties and it can be extended to treat also Gödel-Löb provability logic. The calculi provide direct decision methods through terminating proof search. Syntactic proofs of modal undefinability results are obtained in the form of conservativity theorems.

The paper outlines and immediately discusses the so-called ‘soft’ impossibility, i.e., non-logical impossibility generated by modal realism. It will be shown that although in a particular case genuine modal realism, straightforwardly applied, deems impossible a proposition that other philosophers have claimed to be (intuitively) possible, there is a variety of methodologically acceptable moves available in order to avoid the problem. The impossibility at issue is the existence of island universes. Given the Lewisian analysis there are three points (...) at which we might try to square genuine modal realism with such a controversial and problematic claim of (im)possibility, namely: a) the contraction of our pre-theoretical opinions about possibility, b) the revision of some Lewisian definitions and/or c) the extension of our ontological commitments. I shall look at each of these approaches applied to the problematic case. (shrink)

Inquiry into the metaphysics of essence tends to be pursued in a realist and model-theoretic spirit, in the sense that metaphysical vocabulary is used in a metalanguage to model truth conditions for the object-language use of essentialist vocabulary. This essay adapts recent developments in proof-theoretic semantics to provide a nominalist analysis for a variety of essentialist vocabularies. A metalanguage employing explanatory inferences is used to individuate introduction and elimination rules for atomic sentences. The object-language assertions of sentences concerning essences (...) are then interpreted as devices for marking off structural features of the explanatory inferences that, under a given interpretation, constitute the contents of the atoms of the language. On this proposal, object-language essentialist vocabulary is mentioned in a proof-theoretic metalanguage that uses a vocabulary of explanation. The result is a nominalist interpretation of essence as a modality, understood in the grammatical sense as a modification of the copula, and a view of metaphysical inquiry that is closely connected to the explanatory commitments present in first-order inquiry into things like sets, chemicals, and organisms. This result illustrates that some of the presuppositions that have animated analytic metaphysics over the last few decades can be profitably substituted with more practice-oriented conceptions of the forms of reasoning at work in different domains of human knowledge. (shrink)

It follows from Humean principles of plenitude, I argue, that island universes are possible: physical reality might have 'absolutely isolated' parts. This makes trouble for Lewis's modal realism; but the realist has a way out. First, accept absolute actuality, which is defensible, I argue, on independent grounds. Second, revise the standard analysis of modality: modal operators are 'plural', not 'individual', quantifiers over possible worlds. This solves the problem of island universes and confers three additional benefits: an 'unqualified' (...) principle of compossibility can be accepted; the possibility of nothing can be accommodated; and the identity of indiscernible worlds can be decisively refuted. (shrink)

Theories of possible worlds abound. Since the introduction of modal logic, the term of a possible world, and the very nature of an entity denoted by the term, have stood on the top of metaphysical inquiries. A possible world, roughly speaking, is a complete way things could have been. On the face of it, whatever is possible takes place in some possible world, and whatever is not possible, does not. The aim of the present book is to argue that (...) even impossible things happen. By taking David Lewis’s Modal Realism (henceforth as “MR”) seriously, I claim that besides infinitely many concrete ways things could have been, there exist ways things could not have been. I call them concrete impossible worlds. In Chapter I, I outline Lewis’s well-defined conception of philosophical analysis. I present its structure, aims, methodology and criteria for success. Besides the virtues of the Lewisian conception, I point out several limitations the theory has and offer very simple solution: the admission of concrete impossible worlds. In Chapter II, I present a version of an epistemological objection against MR and a positive account in favour of Modal Fictionalism (henceforth as “MF”). I then present the puzzle in this matter and attempt to generalise my point. 9 Introduction Chapter III demonstrates how flexible Lewis’s theory is. I consider a putative impossibility of there being island universes – spatiotemporally disjoint spacetimes – and show what a proponent of modal realism can do in order to account for it. I present three possible moves: a revision of our pre-theoretical opinions, a modification of our definitions and, finally, an ex- tension of our metaphysical commitments. I consider two ersatz theories of impossible worlds in Chapter IV. In particular, I scrutinize Franz Berto’s and Edwin Mares’s (hybrid) theories of MR. Although I admit that the theories radically extend the scope of applications of MR without extending its metaphysical commitments, the approaches do have some limits. Finally, in Chapter V, I present Extended Modal Realism (henceforth EMR), a theory according to which the best way to go in order to account for impossible phenomena is to ex- tend our metaphysical base by genuine impossibilia. I try to (at least) weaken, if not meet, the crucial objections to the proposal. Namely, I challenge the proclaimed universality of classical logic and, subsequently, motivate certain kind of paraconsistent approach to modal reality. Although the consequences are very hard to swallow, I argue that it is because of the fact that we are unsure of our pre-theoretical opinions concerning the impossible. (shrink)

Superlative adjectives accompanied by certain modal adjectives like possible (e.g. John bought the largest possible present) are ambiguous between a reading where possible is a regular noun modifier and a reading paraphrasable as ‘as Adj as possible’, called ‘modal superlative reading’. Three interesting restrictions have been observed in the literature. First, possible and some other adjectives ending in -able, but not potential and probable, support the latter reading. Second, when the modal adjective appears postnominally, only the (...) class='Hi'>modal superlative reading is available. Third, prenominal possible needs to be in a local configuration to -est in order for the modal superlative reading to arise. Using LF structures independently motivated for degree constructions, the present paper develops a compositional semantic analysis of the modal superlative reading, makes correct new predictions concerning this reading, and—by reconciling previous, opposed syntactic analyses—allows us to derive the three empirical restrictions above. The key innovations are: (i) the previously proposed constituent [possible ▲ellipsis] is interpreted as an amount relative clause, and (ii) this constituent is treated as overtly expressing the comparison class argument of -est. (shrink)

We use a mechanized verification system, PVS, to examine the argument from Anselm’s Proslogion Chapter III, the so-called “Modal Ontological Argument.” We consider several published formalizations for the argument and show they are all essentially similar. Furthermore, we show that the argument is trivial once the modal axioms are taken into account. This work is an illustration of Computational Philiosophy and, in addition, shows how these methods can help detect and rectify errors in modal reasoning.

This chapter provides a selective survey of prominent theories of the semantics of deontic modals in logic and natural language. We focus on Kratzer’s (1977; 1981; 1991) semantics and extensions to this analysis. Kratzer’s semantics has been far and away the most influential theory of deontic modals, which provide a base case for the interpretation of normative language in general. Understanding the logic and truth-conditions of normative language is one of the core areas of metaethics. It informs our understanding (...) of normative arguments and normative reasoning. As this chapter will emphasize, some forms of normative language don’t allow for the inferences that classical logic trains philosophers to expect. Understanding what inferences are valid for normative language should impact our under-standing of how we reason, and should reason, about the normative. We will first look at how deontic modals are understood in the context of modal logic and natural language. Then we’ll survey some recent debates and discoveries in the literature on deontic modals in natural language. We close with some considerations about the relevance of natural language to metaethics. (shrink)

A proper understanding of agentive modals promises to clarify issues to do with free will, know how, and other philosophically interesting topics. In this paper I identify one constraint on, and one structural feature of, trying-based versions of the conditional analysis of the agentive modals. I suggest that the constraint and structural feature together provide a novel account of why the famous Lehrer-Chisholm objection to conditional analyses of ability modals is so powerful. I argue that Mandelkern et al.’s ‘Agentive (...) Modals’ (Philosophical Review,126/3, 301–343, 2017) conditional analysis of the agentive modals fails to avoid this problem. I also identify two further problems for their account. I close by summarising a number of criteria which any successful semantic analysis of the agentive modals should satisfy. (shrink)

We do a quantitative analysis of modal logic. For example, for each Kripke structure M, we study the least ordinal μ such that for each state of M, the beliefs of up to level μ characterize the agents' beliefs (that is, there is only one way to extend these beliefs to higher levels). As another example, we show the equivalence of three conditions, that on the face of it look quite different, for what it means to say that (...) the agents' beliefs have a countable description, or putting it another way, have a "countable amount of information". The first condition says that the beliefs of the agents are those at a state of a countable Kripke structure. The second condition says that the beliefs of the agents can be described in an infinitary language, where conjunctions of arbitrary countable sets of formulas are allowed. The third condition says that countably many levels of belief are sufficient to capture all of the uncertainty of the agents (along with a technical condition). The fact that all of these conditions are equivalent shows the robustness of the concept of the agents' beliefs having a "countable description". (shrink)

Discussions on the concept of Marifatullah as the foundation of belief hold a significant place in theology. There are different opinions among schools of theology regarding whether those who do not receive divine messages must know God. The majority of scholars belonging to the Mu'tazila and Māturīdī schools, including Imam Māturīdī, state that human beings must know God. Although al-Ashʿarī accepts that the most prominent obligatory duties are the methods of reasoning that lead to marifatullah, he states that responsibility in (...) this matter is formed by transmission. However, we can say that whether the human mind is sufficient to reach the knowledge of God, the method of reasoning has reached a different dimension today from the sciences of psychology, genetics, and neurobiology. This study explored whether individuals can achieve marifatullah from a holistic perspective. Whether human beings can be held responsible for this issue has been evaluated through the sciences of psychology, genetics, and neurobiology, and the opinions of schools of theology on this issue have been criticized. When we think in terms of Marifatullah, we can say that man’s psychological sense of obligation to adapt to society leaves him intellectually under the influence of society. In terms of genetic determinism, human personality, behavior, and intellectual adventure are completely determined by genes. Therefore, it is impossible for men to reach marifatullah in the context of their mental abilities. From an epigenetic perspective, we see that human thought structure, behavior, and personality are formed as a result of interactions with the environment. Serious hesitation arises in this idea in terms of intellect being a source of responsibility. Humans are genetically influenced by the environment and society, and they have a suitable nature for this, revealing that their genetic structure is open to environmental influences. In terms of brain plasticity, factors such as the society, environment, and family in which people live can change their brains and enable them to live accordingly. Although life adventures appear to be within the framework of social harmony, there must also be intellectual and religious harmony within social harmony. This reinforces the idea that individuals tend to align more with the thoughts and beliefs instilled by culture given the adaptable nature of the human brain influenced by cultural factors. When the views of the schools of theology are considered considering these evaluations, it becomes clear that the Mu'tazilites and Māturīdīs' belief that the source of the wujūb of marifatullah is intellect is at a point that needs to be reconsidered in terms of human biology and psychology. Although the Asharites emphasize human beings attaining knowledge of God through intellect, their focus on prophethood indicates that a revelation offer appears more accurate concerning human nature in the context of Marifatullah. (shrink)

The Semantic-Pragmatic Analysis of Persian Modal Verbs Based on Papafragou's Model This paper aims at analyzing the semantics and pragmatics of Persian modal verbs based on Papafragou's relevance-theoretic model. Persian modals are defined in terms of logical relations and propositional domains. According to the findings of the research, two of the three modals, namely, šodan and tavân express the logical relation of compatibility with respect to different propositional domains: the three forms mišavad, mišod and mišode are unspecified (...) with respect to their propositional domains and take them directly from the context, whereas betavân and bešavad accept the desirability domain. Mitavân also expresses compatibility in relation to the propositions in the factual domain. However, bˇyad is the only modal that encodes the logical relation of entailment and is unspecified with respect to the type of propositional domain it accepts. (shrink)

Induction, conceived as the class of rational non-truth preserving inferences, has been a perennial problem in philosophy. Aside from the problem of justification of induction, a less debated issue is the problem of properly describing inductive inferences. The purpose of this book is to conceptually investigate this descriptive problem of induction from the standpoint of the nonmonotonic logical tradition raised inside the field of Artificial Intelligence in the last thirty years. As we try to show, an essential part of this (...) enterprise involves the analysis of a pragmatically oriented notion of probability, called by us inductive plausibility. This in turn is made from the viewpoint of paraconsistency ? which according to some is the unavoidable companion of nonmonotonicity ? and modal logic. We therefore put forward a nonmonotonic, paraconsistent and modal approach to induction and plausibility. The book shall be useful to philosophers, logicians and computer scientists interested in the problem of induction in general and in the logical analysis of induction and plausibility in particular. (shrink)

Some argue that Lewisian realism fails as a reduction of modality because in order to meet some criterion of success the account needs to invoke primitive modality. I defend Lewisian realism against this charge; in the process, I hope to shed some light on the conditions of success for a reduction. In §1 I detail the resources the Lewisian modal realist needs. In §2 I argue against Lycan and Shalkowski’s charge that Lewis needs a modal notion of ‘world’ (...) to ensure that worlds correspond to possibilities. In §3 I respond to Divers and Melia’s objection that Lewis needs to invoke primitive modality to give a complete account of what worlds there are. In §4 I ask what it is for a notion to ‘involve’ modality. I conclude that the question is either in bad standing or at best offers little traction on the debate, and propose a different way of assessing when materials are appropriately included in a reductive base. (shrink)

ABSTRACT This paper reports on an empirical performance analysis of four modal theorem provers on benchmark suites of randomly generated formulae. The theorem provers tested are the Davis-Putnam-based procedure KSAT, the tableaux-based system KRZIS, the sequent-based Logics Workbench, and a translation approach combined with the first-order theorem prover SPASS. Our benchmark suites are sets of multi-modal formulae in a certain normal form randomly generated according to the scheme of Giunchiglia and Sebastiani [GS 96a, GS 96b]. We investigate (...) the quality of the random modal formulae and show that the scheme has some shortcomings, which may lead to mistaken conclusions. We propose improvements to the evaluation method and show that the translation approach provides a viable alternative to the other approaches. (shrink)

Three variants of Kurt Gödel's ontological argument, proposed by Dana Scott, C. Anthony Anderson and Melvin Fitting, are encoded and rigorously assessed on the computer. In contrast to Scott's version of Gödel's argument the two variants contributed by Anderson and Fitting avoid modal collapse. Although they appear quite different on a cursory reading they are in fact closely related. This has been revealed in the computer-supported formal analysis presented in this article. Key to our formal analysis is (...) the utilization of suitably adapted notions of ultrafilters, and a careful distinction between extensions and intensions of positive properties. (shrink)

Modals in St’át’imcets (Lillooet Salish) show two differences from their counterparts in English. First, they have variable quantificational force, systematically allowing both possibility and necessity interpretations; and second, they lexically restrict the conversational background, distinguishing for example between deontic and (several kinds of) epistemic modality. We provide an analysis of the St’át’imcets modals according to which they are akin to specific indefinites in the nominal domain. They introduce choice function variables which select a subset of the accessible worlds. Following (...) Klinedinst, we assume distributivity over the resulting set of worlds. St’át’imcets modals thus receive a uniform interpretation as (distributive) pluralities. The appearance of variability in modal force arises because the choice function can select a larger or smaller subset of accessible worlds. Finally, we discuss the implications of our analysis for the investigation of modal systems in other languages. (shrink)

Modal logic has been applied in many different areas, as reasoning about time, knowledge and belief, necessity and possibility, to mention only some examples. In the present paper, an attempt is made to use modal logic to account for the semantics of theoretical sentences in scientific language. Theoretical sentences have been studied extensively since the work of Ramsey and Carnap. The present attempt at a modal analysis is motivated by there being several intended interpretations of the (...) theoretical terms once these terms are introduced through the axioms of a theory. (shrink)

According to Thagard and Stewart :1–33, 2011), creativity results from the combination of neural representations, and combination results from convolution, an operation on vectors defined in the holographic reduced representation framework. They use these ideas to understand creativity as it occurs in many domains, and in particular in science. We argue that, because of its algebraic properties, convolution alone is ill-suited to the role proposed by Thagard and Stewart. The semantic pointer concept allows us to see how we can apply (...) the full range of HRR operations while keeping the modal representations so central to Thagard and Stewart’s theory. By adding another combination operation and using semantic pointers as the combinatorial basis, this modified version overcomes the limitations of the original theory and perhaps helps us explain aspects of creativity not covered by the original theory. While a priori reasons cast doubts on the use of HRR operations with modal representations :5039–5054, 1987) such as semantic pointers, recent models point in the other direction, allowing us to be optimistic about the success of the revised version. (shrink)

In the presentation I will analyse Kant’s conception of modalities and consider its relevance to his critical metaphysics. With his Tables of Judgements and of Categories Kant makes an important division between two kinds of modality, of which the former is only logical and the latter transcendental, i.e., objective. Only judgements that are necessary in both ways are properly metaphysical. This distinction is important for Kant’s distinction between Transcendental Analytic and Transcendental Dialectic, i.e., between acceptable and unacceptable metaphysics. I submit (...) that not only is Kant’s theory of modality useful for properly understanding his arguments in the Dialectic, but that only by distinguishing between the two types of modality can one can make sense of his theory that the ideas of reason are simultaneously inevitable and erroneous. This modal analysis thus offers a new and important point of view to Kant’s metaphysics and its critique. (shrink)

This paper provides a semantic analysis of the particles afinal (European Portuguese) and alla fine (Italian) in terms of the notion of truth unpersistence, which can be situated at the intersection of epistemic modality and discourse structure. In the analysis proposed, the particles are propositional operators and require that the truth of a proposition p* fail to persist through a temporal succession of epistemic states, this proposition being incompatible with the prejacent, and that the interlocutors share knowledge of (...) a previous epistemic attitude toward p*. We analyze two main cases (plan-related and non plan-related propositions) and also show that these particles are indexical to one (or more) epistemic agent(s) and allow for shifts in perspective. (shrink)

We discuss the semantic significance of a puzzle concerning ‘ought’ and conditionals recently discussed by Kolodny and MacFarlane. We argue that the puzzle is problematic for the standard Kratzer-style analysis of modality. In Kratzer’s semantics, modals are evaluated relative to a pair of conversational backgrounds. We show that there is no sensible way of assigning values to these conversational backgrounds so as to derive all of the intuitions in Kolodny and MacFarlane’s case. We show that the appropriate verdicts can (...) be derived by extending Kratzer’s framework to feature a third conversational background and claiming that the relevant reading of ‘ought’ is sensitive to this parameter. (shrink)

Relativized Metaphysical Modality (RMM: Murray and Wilson, 'Relativized metaphysical modality', Oxford Studies in Metaphysics, 2012; Murray, Perspectives on Modal Metaphysics, 2017) exploits 'two-dimensionalist' resources to metaphysical, rather than epistemological, ends: the second dimension offers perspective-dependence without contingency, diverting attacks on 'Classical' analyses of modals (in effect, analyses validating S5 and the Barcan Formulae). Here, we extend the RMM program in two directions. First, we harvest resources for RMM from Lewis's 1980 'Context--Index' (CI) framework: (a) the ban in CI on (...) binding into context-arguments (akin to Kaplan's 'monstrosity' ban) projects a bright line between perspective-dependence and contingency; and (b) CI-postulated connections among meaning, content, truth, argument-structure, context, and modality collectively generate a 'Generalized Humphrey Problem' for any non-Classical analysis (examples covered include appeals to accessibility, contingent domains, and counterpart relations). Second, we sharpen the tools of RMM-based metaphysical analysis, and extend their domain of coverage across familiar anomalies for Classical modals: we revisit earlier RMM-based bulwarks for S5 (against 'Chisholm's Paradox' for moderate flexibility of essence, and nomological necessitarianism); and we now similarly shore up the Barcan Formulae (against the apparent contingency of existence and nonexistence). (shrink)

According to the modal view, essence admits of reductive analysis in exclusively modal terms. Fine (1994) argues that modal view delivers an inadequate analysis of essence. This paper defends the modal view from Fine's challenge. This defense proceeds by examining the disagreement between Finean primitivists and Quinean eliminativists about essence. In order to model this disagreement, a distinction between essence and a separable concept, nature, is required. This distinction is then used to show that (...) Fine's challenge is misdirected and therefore unsuccessful. (shrink)

According to Thagard and Stewart :1–33, 2011), creativity results from the combination of neural representations, and combination results from convolution, an operation on vectors defined in the holographic reduced representation framework. They use these ideas to understand creativity as it occurs in many domains, and in particular in science. We argue that, because of its algebraic properties, convolution alone is ill-suited to the role proposed by Thagard and Stewart. The semantic pointer concept allows us to see how we can apply (...) the full range of HRR operations while keeping the modal representations so central to Thagard and Stewart’s theory. By adding another combination operation and using semantic pointers as the combinatorial basis, this modified version overcomes the limitations of the original theory and perhaps helps us explain aspects of creativity not covered by the original theory. While a priori reasons cast doubts on the use of HRR operations with modal representations :5039–5054, 1987) such as semantic pointers, recent models point in the other direction, allowing us to be optimistic about the success of the revised version. (shrink)

Summary: The paper provides an argument for modal primitivism, the view that necessity is not defined and is therefore part of the structure of reality. It then raises the explanation-challenge for primitivists: how can modal truths be explained by hyper-intensional truths, if necessity is not defined in terms of hyper-intensional phenomena? To address the challenge, the paper introduces 'sophisticated modal primitivism' which gives a substantive analysis of the notion of a 'source of necessity'. The final part (...) of the paper offers some applications of that novel piece of ideology. (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)

Minimalists about truth think they've hit on something like a job description for a truth predicate: A truth predicate facilitates the expression of certain generalizations, such as "Whatever N. said is true" that would otherwise require a substitutional quantifier, or an infinite conjunction or disjunction. In the first chapter I argue that even if truth predicates have that function, it would be a mistake to suppose that this is their only role. There is an internal relation between truth and assertion (...) that a minimalist fails to capture. In order to demonstrate this, I show how on a minimalist view commands would end up being among the sorts of things which are apt for truth. In the second chapter, I consider Lewis' well-known "argument from paraphrase" for the existence of possible worlds. I claim that the argument is only compelling on a certain reading of the presumption in favor of a face value semantics, but that on this reading the conclusion of the argument is incompatible with any standard possible worlds analysis of modal discourse. I go on to consider both whether the presumption in favor of a face value analysis of "way" talk might be defeated, and if not, how an ontic analysis of modal discourse might be recast in a form consistent with this result. ;In the third chapter, I consider a paradox involving our first-order modal judgements: It seems consistent to suppose that some things which are not possible still could have been possible if only the world had been different. But this is a view that's hard to square with a plausible semantics for modality. I argue that the problem here is a genuine puzzle about modality and that it requires the introduction of a perspectival semantics for attributions of de re modal properties. (shrink)

We analyze the precise modal commitments of several natural varieties of set-theoretic potentialism, using tools we develop for a general model-theoretic account of potentialism, building on those of Hamkins, Leibman and Löwe [14], including the use of buttons, switches, dials and ratchets. Among the potentialist conceptions we consider are: rank potentialism, Grothendieck–Zermelo potentialism, transitive-set potentialism, forcing potentialism, countable-transitive-model potentialism, countable-model potentialism, and others. In each case, we identify lower bounds for the modal validities, which are generally either S4.2 (...) or S4.3, and an upper bound of S5, proving in each case that these bounds are optimal. The validity of S5 in a world is a potentialist maximality principle, an interesting set-theoretic principle of its own. The results can be viewed as providing an analysis of the modal commitments of the various set-theoretic multiverse conceptions corresponding to each potentialist account. (shrink)

I argue for an analysis of conceivability as a form of modal knowledge: to conceive of p's being true is to know that "Possibly, p" is true.

We show in this paper that some expressions indicating source of evidence are part of propositional content and are best analyzed as special kind of epistemic modal. Our evidence comes from the Japanese evidential system. We consider six evidentials in Japanese, showing that they can be embedded in conditionals and under modals and that their properties with respect to modal subordination are similar to those of ordinary modals. We show that these facts are difficult for existing theories of (...) evidentials, which assign evidentials necessarily widest scope, to explain. We then provide an analysis using a logical system designed to account for evidential reasoning; this logic is the first developed system of probabilistic dynamic predicate logic. This analysis is shown to account for the data we provide that is problematic for other theories. (shrink)