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1370Impossible WorldsNoûs 47 (3): 713-728. 2013.Impossible worlds are representations of impossible things and impossible happenings. They earn their keep in a semantic or metaphysical theory if they do the right theoretical work for us. As it happens, a worlds-based account provides the best philosophical story about semantic content, knowledge and belief states, cognitive significance and cognitive information, and informative deductive reasoning. A worlds-based story may also provide the best semantics for counterfactuals. But to function …Read more
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31Reality Making (edited book)Oxford University Press UK. 2016.What makes up reality, and how? What kinds of entity are fundamental to reality, and how do dependent entities depend on the fundamental ones? How does one entity metaphysically ground another? These questions are central to contemporary metaphysics. The papers in this collection, written by a new generation of metaphysicians, address these and related questions. They investigate the metaphysical concepts of grounding and fundamentality, and the relationship between the fundamental and all the o…Read more
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630Logical information and epistemic spaceSynthese 167 (2). 2009.Gaining information can be modelled as a narrowing of epistemic space . Intuitively, becoming informed that such-and-such is the case rules out certain scenarios or would-be possibilities. Chalmers’s account of epistemic space treats it as a space of a priori possibility and so has trouble in dealing with the information which we intuitively feel can be gained from logical inference. I propose a more inclusive notion of epistemic space, based on Priest’s notion of open worlds yet which contains …Read more
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158Epistemic logic for rule-based agentsJournal of Logic, Language and Information 18 (1): 131-158. 2009.The logical omniscience problem, whereby standard models of epistemic logic treat an agent as believing all consequences of its beliefs and knowing whatever follows from what else it knows, has received plenty of attention in the literature. But many attempted solutions focus on a fairly narrow specification of the problem: avoiding the closure of belief or knowledge, rather than showing how the proposed logic is of philosophical interest or of use in computer science or artificial intelligence.…Read more
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170Indexicals, fictions, and fictaDialectica 57 (2). 2003.We defend the view that an indexical uttered by an actor works on the model of deferred reference. If it defers to a character which does not exist, it is an empty term, just as ‘Hamlet’ and ‘Ophelia’ are. The utterance in which it appears does not express a proposition and thus lacks a truth value. We advocate an ontologically parsimonious, anti-realist, position. We show how the notion of truth in our use and understanding of indexicals (and fictional names) as they appear within a fiction is …Read more
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2230Recent Work in Relevant LogicAnalysis 73 (3): 526-541. 2013.This paper surveys important work done in relevant logic in the past 10 years.
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922The cost of truthmaker maximalismCanadian Journal of Philosophy 43 (4): 460-474. 2013.According to truthmaker theory, particular truths are true in virtue of the existence of particular entities. Truthmaker maximalism holds that this is so for all truths. Negative existential and other ‘negative’ truths threaten the position. Despite this, maximalism is an appealing thesis for truthmaker theorists. This motivates interest in parsimonious maximalist theories, which do not posit extra entities for truthmaker duty. Such theories have been offered by David Lewis and Gideon Rosen, Ros…Read more
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1171Advanced Modalizing ProblemsMind 125 (499): 627-642. 2016.I present an internal problem for David Lewis’s genuine modal realism. My aim is to show that his analysis of modality is inconsistent with his metaphysics. I consider several ways of modifying the Lewisian analysis of modality, but argue that none are successful. I argue that the problem also affects theories related to genuine modal realism, including the stage theory of persistence and modal fictionalism.
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436Syntactic logics do not suffer from the problems of logical omniscience but are often thought to lack interesting properties relating to epistemic notions. By focusing on the case of rule-based agents, I develop a framework for modelling resource-bounded agents and show that the resulting models have a number of interesting properties.
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6068Being Positive About Negative FactsPhilosophy and Phenomenological Research 85 (1): 117-138. 2012.Negative facts get a bad press. One reason for this is that it is not clear what negative facts are. We provide a theory of negative facts on which they are no stranger than positive atomic facts. We show that none of the usual arguments hold water against this account. Negative facts exist in the usual sense of existence and conform to an acceptable Eleatic principle. Furthermore, there are good reasons to want them around, including their roles in causation, chance-making and truth-making, and…Read more
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162Preference-based belief revision for rule-based agentsSynthese 165 (2): 159-177. 2008.Agents which perform inferences on the basis of unreliable information need an ability to revise their beliefs if they discover an inconsistency. Such a belief revision algorithm ideally should be rational, should respect any preference ordering over the agent’s beliefs (removing less preferred beliefs where possible) and should be fast. However, while standard approaches to rational belief revision for classical reasoners allow preferences to be taken into account, they typically have quite hig…Read more
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1317Monism and Material ConstitutionPacific Philosophical Quarterly 95 (1): 189-204. 2014.Are the sculpture and the mass of gold which permanently makes it up one object or two? In this article, we argue that the monist, who answers ‘one object’, cannot accommodate the asymmetry of material constitution. To say ‘the mass of gold materially constitutes the sculpture, whereas the sculpture does not materially constitute the mass of gold’, the monist must treat ‘materially constitutes’ as an Abelardian predicate, whose denotation is sensitive to the linguistic context in which it appear…Read more
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218Setting the Facts StraightJournal of Philosophical Logic 40 (1): 33-54. 2011.Substantial facts are not well-understood entities. Many philosophers object to their existence on this basis. Yet facts, if they can be understood, promise to do a lot of philosophical work: they can be used to construct theories of property possession and truthmaking, for example. Here, I give a formal theory of facts, including negative and logically complex facts. I provide a theory of reduction similar to that of the typed λ -calculus and use it to provide identity conditions for facts. Thi…Read more
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8Modelling communicating agents in timed reasoning logicsIn U. Endriss & M. Baldoni (eds.), Declarative Agent Languages and Technologies 4, Springer. 2006.Practical reasoners are resource-bounded—in particular they require time to derive consequences of their knowledge. Building on the Timed Reasoning Logics (TRL) framework introduced in [1], we show how to represent the time required by an agent to reach a given conclusion. TRL allows us to model the kinds of rule application and conflict resolution strategies commonly found in rule-based agents, and we show how the choice of strategy can influence the information an agent can take into account w…Read more
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443Grounding is a powerful metaphysical concept; yet there is widespread scepticism about the intelligibility of the notion. In this paper, I propose an account of an entity’s nature or essence, which I then use to provide grounding conditions for that entity. I claim that an understanding of an entity’s nature, together with an account of how logically complex entities are grounded, provides all we need to understand how that entity is grounded. This approach not only allows us to say what grounds…Read more
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494Alethic undecidability doesn’t solve the LiarAnalysis 76 (3): 278-283. 2016.Stephen Barker presents a novel approach to solving semantic paradoxes, including the Liar and its variants and Curry’s paradox. His approach is based around the concept of alethic undecidability. His approach, if successful, renders futile all attempts to assign semantic properties to the paradoxical sentences, whilst leaving classical logic fully intact. And, according to Barker, even the T-scheme remains valid, for validity is not undermined by undecidable instances. Barker’s approach is inno…Read more
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1445The Problem of Rational KnowledgeErkenntnis (S6): 1-18. 2013.Real-world agents do not know all consequences of what they know. But we are reluctant to say that a rational agent can fail to know some trivial consequence of what she knows. Since every consequence of what she knows can be reached via chains of trivial cot be dismissed easily, as some have attempted to do. Rather, a solution must give adequate weight to the normative requirements on rational agents’ epistemic states, without treating those agents as mathematically ideal reasoners. I’ll argue …Read more
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260The Impossible: An Essay on HyperintensionalityOxford University Press. 2014.Mark Jago presents an original philosophical account of meaningful thought: in particular, how it is meaningful to think about things that are impossible. We think about impossible things all the time. We can think about alchemists trying to turn base metal to gold, and about unfortunate mathematicians trying to square the circle. We may ponder whether God exists; and philosophers frequently debate whether properties, numbers, sets, moral and aesthetic qualities, and qualia exist. In many philo…Read more
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949Constructing worldsSynthese 189 (1): 59-74. 2012.You and I can differ in what we say, or believe, even though the things we say, or believe, are logically equivalent. Discussing what is said, or believed, requires notions of content which are finer-grained than sets of (metaphysically or logically) possible worlds. In this paper, I develop the approach to fine-grained content in terms of a space of possible and impossible worlds. I give a method for constructing ersatz worlds based on theory of substantial facts. I show how this theory overcom…Read more
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79Resource-bounded belief revision and contractionIn P. Torroni, U. Endriss, M. Baldoni & A. Omicini (eds.), Declarative Agent Languages and Technologies III, Springer. pp. 141--154. 2006.Agents need to be able to change their beliefs; in particular, they should be able to contract or remove a certain belief in order to restore consistency to their set of beliefs, and revise their beliefs by incorporating a new belief which may be inconsistent with their previous beliefs. An influential theory of belief change proposed by Alchourron, G¨ardenfors and Makinson (AGM) [1] describes postulates which a rational belief revision and contraction operations should satisfy. The AGM postulat…Read more
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728Imagine the possibilities: information without overloadLogique Et Analyse 49 (196). 2006.Information is often modelled as a set of relevant possibilities, treated as logically possible worlds. However, this has the unintuitive consequence that the logical consequences of an agent's information cannot be informative for that agent. There are many scenarios in which such consequences are clearly informative for the agent in question. Attempts to weaken the logic underlying each possible world are misguided. Instead, I provide a genuinely psychological notion of epistemic possibility a…Read more
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44Verifying Space and Time Requirements for Resource-Bounded AgentsIn A. Lomuscio & S. Edelkamp (eds.), Model Checking and Artificial Intelligence, Springer. 2007.The effective reasoning capability of an agent can be defined as its capability to infer, within a given space and time bound, facts that are logical consequences of its knowledge base. In this paper we show how to determine the effective reasoning capability of an agent with limited memory by encoding the agent as a transition system and automatically verifying whether a state where the agent believes a certain conclusion is reachable from the start state. We present experimental results using …Read more
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603Modal Realism, Still At Your ConvenienceAnalysis. 2016.Divers (2014) presents a set of de re modal truths which, he claims, are inconvenient for Lewisean modal realism. We argue that there is no inconvenience for Lewis.
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1023The Conjunction and Disjunction ThesesMind 118 (470): 411-415. 2009.Rodriguez-Pereyra (2006) argues for the disjunction thesis but against the conjunction thesis. I argue that accepting the disjunction thesis undermines his argument against the conjunction thesis.
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612Hintikka and Cresswell on Logical OmniscienceLogic and Logical Philosophy 15 (3): 325-354. 2006.I discuss three ways of responding to the logical omniscience problems faced by traditional ‘possible worlds’ epistemic logics. Two of these responses were put forward by Hintikka and the third by Cresswell; all three have been influential in the literature on epistemic logic. I show that both of Hintikka's responses fail and present some problems for Cresswell’s. Although Cresswell's approach can be amended to avoid certain unpalatable consequences, the resulting formal framework collapses to a…Read more
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1170Against Yagisawa's modal realismAnalysis 73 (1): 10-17. 2013.In his book Worlds and Individuals, Possible and Otherwise (2010), Takashi Yagisawa presents and argues for a novel and imaginative version of modal realism. It differs both from Lewis’s modal realism (Lewis 1986) and from actualists’ ersatz accounts (Adams 1974; Sider 2002). In this paper, I’ll present two arguments, each of which shows that Yagisawa’s metaphysics is incoherent. The first argument shows that the combination of Yagisawa’s metaphysics with impossibilia leads to triviality: every …Read more
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1178The Problem with Truthmaker-Gap EpistemicismThought: A Journal of Philosophy 1 (4): 320-329. 2012.Epistemicism about vagueness is the view that vagueness, or indeterminacy, is an epistemic matter. Truthmaker-gap epistemicism is the view that indeterminate truths are indeterminate because their truth is not grounded by any worldly fact. Both epistemicism in general and truthmaker-gap epistemicism originated in Roy Sorensen's work on vagueness. My aim in this paper is to give a characterization of truthmaker-gap epistemicism and argue that the view is incompatible with higher-order vagueness: …Read more
Nottingham, Nottingham, United Kingdom of Great Britain and Northern Ireland
Areas of Specialization
Metaphysics |
Logic and Philosophy of Logic |
Philosophy of Language |
Epistemology |
Areas of Interest
Epistemology |
Metaphilosophy |
Philosophy of Language |
Logic and Philosophy of Logic |