•  512
    Bananas enough for time travel?
    British Journal for the Philosophy of Science 48 (3): 363-389. 1997.
    This paper argues that the most famous objection to backward time travel can carry no weight. In its classic form, the objection is that backward time travel entails the occurrence of impossible things, such as auto-infanticide—and hence is itself impossible. David Lewis has rebutted the classic version of the objection: auto-infanticide is prevented by coincidences, such as time travellers slipping on banana peels as they attempt to murder their younger selves. I focus on Paul Horwich‘s more re…Read more
  •  334
    Orthodoxy has it that mereological composition can never be a vague matter, for if it were, then existence would sometimes be a vague matter too, and that's impossible. I accept that vague composition implies vague existence, but deny that either is impossible. In this paper I develop degree-theoretic versions of quantified modal logic and of mereology, and combine them in a framework that allows us to make clear sense of vague composition and vague existence, and the relationships between them
  •  303
    Why Would Time Travelers Try to Kill Their Younger Selves?
    The Monist 88 (3): 388-395. 2005.
    In this note I raise a new problem for backwards time travel, and make some first suggestions as to how it might be solved. I call it the motivation problem. It is not a logical or a metaphysical problem, but a psychological one. It does not impact upon the possibility, or even the likelihood, of backwards time travel. Yet it is deeply puzzling, and we will have no idea what time travel would actually be like until we explore it. Thus, where other problems for backward time travel assume that we…Read more
  •  245
    Inconsistency in the A-Theory
    Philosophical Studies 156 (2). 2011.
    This paper presents a new argument against A-theories of time. A-theorists hold that there is an objective now (present moment) and an objective flow of time, the latter constituted by the movement of the objective now through time. A-theorists therefore want to draw different pictures of reality—showing the objective now in different positions—depending upon the time at which the picture is drawn. In this paper it is argued that the times at which the different pictures are drawn may be taken t…Read more
  •  229
    The Paradoxes of Time Travel
    with Ken Perszyk
    In Public lecture at Te Papa (National Museum of New Zealand), . 2001.
    Humans have long been fascinated by the idea of visiting the past and of seeing what the future will bring. Time travel has been one of the most popular themes of science fiction. Most people have seen the TV series ‘Dr Who’ or ‘Quantum Leap’ or ‘Star Trek’. You’ve probably seen one of the ‘Back to the Future’ or ‘Terminator’ movies, or ‘Twelve Monkeys’. Time travel narratives provide fascinating plots, which exercise our imaginations in ever so many ways. But is the idea of travelling forward a…Read more
  •  192
    Graham Priest (1994) has argued that the following paradoxes all have the same structure: Russell’s Paradox, Burali-Forti’s Paradox, Mirimanoff’s Paradox, König’s Paradox, Berry’s Paradox, Richard’s Paradox, the Liar and Liar Chain Paradoxes, the Knower and Knower Chain Paradoxes, and the Heterological Paradox. Their common structure is given by Russell’s Schema: there is a property φ and function δ such that..
  •  191
    Degree of belief is expected truth value
    In Sebastiano Moruzzi & Richard Dietz (eds.), Cuts and Clouds. Vaguenesss, its Nature and its Logic, Oxford University Press. pp. 491--506. 2009.
    A number of authors have noted that vagueness engenders degrees of belief, but that these degrees of belief do not behave like subjective probabilities. So should we countenance two different kinds of degree of belief: the kind arising from vagueness, and the familiar kind arising from uncertainty, which obey the laws of probability? I argue that we cannot coherently countenance two different kinds of degree of belief. Instead, I present a framework in which there is a single notion of degree of…Read more
  •  150
    One of the most striking differences between Frege's Begriffsschrift (logical system) and standard contemporary systems of logic is the inclusion in the former of the judgement stroke: a symbol which marks those propositions which are being asserted , that is, which are being used to express judgements . There has been considerable controversy regarding both the exact purpose of the judgement stroke, and whether a system of logic should include such a symbol. This paper explains the intended rol…Read more
  •  133
    Vagueness as closeness
    Australasian Journal of Philosophy 83 (2). 2005.
    This paper presents and defends a definition of vagueness, compares it favourably with alternative definitions, and draws out some consequences of accepting this definition for the project of offering a substantive theory of vagueness. The definition is roughly this: a predicate 'F' is vague just in case for any objects a and b, if a and b are very close in respects relevant to the possession of F, then 'Fa' and 'Fb' are very close in respect of truth. The definition is extended to cover vaguene…Read more
  •  130
    Fuzzy Logic and Higher-Order Vagueness
    In Petr Cintula, Christian G. Fermüller, Lluis Godo & Petr Hájek (eds.), Understanding Vagueness: Logical, Philosophical and Linguistic Perspectives, College Publications. pp. 1--19. 2011.
    The major reason given in the philosophical literature for dissatisfaction with theories of vagueness based on fuzzy logic is that such theories give rise to a problem of higherorder vagueness or artificial precision. In this paper I first outline the problem and survey suggested solutions: fuzzy epistemicism; measuring truth on an ordinal scale; logic as modelling; fuzzy metalanguages; blurry sets; and fuzzy plurivaluationism. I then argue that in order to decide upon a solution, we need to und…Read more
  •  127
    Vagueness by numbers? No worries
    Mind 112 (446): 283-290. 2003.
    Rosanna Keefe (`Vagueness by Numbers' MIND 107 1998 565--79) argues that theories of vagueness based upon fuzzy logic and set theory rest on a confusion: once we have assigned a number to an object to represent (for example) its *height*, there is no distinct purpose left to be served by assigning a number to the object to represent its *degree of tallness*; she claims that ``any numbers assigned in an attempt to capture the vagueness of `tall' do no more than serve as another measure of h…Read more
  •  123
    Vagueness and blurry sets
    Journal of Philosophical Logic 33 (2): 165-235. 2004.
    This paper presents a new theory of vagueness, which is designed to retain the virtues of the fuzzy theory, while avoiding the problem of higher-order vagueness. The theory presented here accommodates the idea that for any statement S₁ to the effect that 'Bob is bald' is x true, for x in [0, 1], there should be a further statement S₂ which tells us how true S₁ is, and so on - that is, it accommodates higher-order vagueness without resorting to the claim that the metalanguage in which the semanti…Read more
  •  114
    In this paper I present a new argument against vague identity — one that is more fundamental than existing arguments — and I also try to explain why we find the idea of vague identity puzzling, in a way that will dispel the puzzlement. In brief, my argument is this: to make clear sense of something, one must at least model it set-theoretically; but due to the special place of identity in set-theoretic models, any vague relation that one does model set-theoretically will not be identity, for real…Read more
  •  109
    Vagueness and Degrees of Truth
    Oxford University Press. 2008.
    In VAGUENESS AND DEGREES OF TRUTH, Nicholas Smith develops a new theory of vagueness: fuzzy plurivaluationism. A predicate is said to be VAGUE if there is no sharply defined boundary between the things to which it applies and the things to which it does not apply. For example, 'heavy' is vague in a way that 'weighs over 20 kilograms' is not. A great many predicates -- both in everyday talk, and in a wide array of theoretical vocabularies, from law to psychology to engineering -- are vague. Smi…Read more
  •  106
    Routledge Encyclopedia of Philosophy. 1993.
    Epiphenomenalism is a theory concerning the relation between the mental and physical realms, regarded as radically different in nature. The theory holds that only physical states have causal power, and that mental states are completely dependent on them. The mental realm, for epiphenomenalists, is nothing more than a series of conscious states which signify the occurrence of states of the nervous system, but which play no causal role. For example, my feeling sleepy does not cause my yawning — ra…Read more
  •  101
    Logic: The Drill
    Princeton University Press. 2012.
    Contains exercises and solutions to accompany Logic: The Laws of Truth by Nicholas J. J. Smith (Princeton University Press, 2012).
  •  96
    Measuring and Modelling Truth
    American Philosophical Quarterly 49 (4): 345-356. 2012.
    Philosophers, linguists and others interested in problems concerning natural language frequently employ tools from logic and model theory. The question arises as to the proper interpretation of the formal methods employed—of the relationship between, on the one hand, the formal languages and their set-theoretic models and, on the other hand, the objects of ultimate interest: natural language and the meanings and truth conditions of its constituent words, phrases and sentences. Two familiar answe…Read more
  •  88
    I’d Do Anything to Change the Past (But I Can’t Do ‘That')
    American Philosophical Quarterly 54 (2): 153-168. 2017.
    This paper addresses a worry about backwards time travel. The worry is that there is something mysteriously inexplicable about the combination of commonplace events that will inevitably conspire to prevent the time traveler from doing something impossible such as killing her younger self. The worry is first distinguished from other problems for backwards time travel concerning its alleged impossibility or improbability. It is then shown that the worry is misplaced: there is in fact no real probl…Read more
  •  81
    Logic: The Laws of Truth
    Princeton University Press. 2012.
    Logic is essential to correct reasoning and also has important theoretical applications in philosophy, computer science, linguistics, and mathematics. This book provides an exceptionally clear introduction to classical logic, with a unique approach that emphasizes both the hows and whys of logic. Here Nicholas Smith thoroughly covers the formal tools and techniques of logic while also imparting a deeper understanding of their underlying rationales and broader philosophical significance. In addit…Read more
  •  79
    Semantic Regularity and the Liar Paradox
    The Monist 89 (1). 2006.
    My task here is the first one. I do present a consistent formal system and claim that it provides a perfect model of natural languages such as English, but this system involves no surprises. It is none other than the standard framework of classical logic and model theory. The real weight of the argument lies in the claim that the classical framework—without alteration or addition—contains the resources to model what happens when we say in English ‘This sentence is not true’.
  •  75
    Many-Valued Logics
    In Gillian Russell & Delia Graff Fara (eds.), The Routledge Companion to Philosophy of Language, Routledge. pp. 636--51. 2012.
    A many-valued (aka multiple- or multi-valued) semantics, in the strict sense, is one which employs more than two truth values; in the loose sense it is one which countenances more than two truth statuses. So if, for example, we say that there are only two truth values—True and False—but allow that as well as possessing the value True and possessing the value False, propositions may also have a third truth status—possessing neither truth value—then we have a many-valued semantics in the loose but…Read more
  •  71
    If we think, as Ramsey did, that a degree of belief that P is a stronger or weaker tendency to act as if P, then it is clear that not only uncertainty, but also vagueness, gives rise to degrees of belief. If I like hot coffee and do not know whether the coffee is hot or cold, I will have some tendency to reach for a cup; if I like hot coffee and know that the coffee is borderline hot, I will have some tendency to reach for a cup. Suppose that we take degrees of belief arising from uncertainty to…Read more
  •  62
    From Fine and Kamp in the 70’s—through Osherson and Smith in the 80’s, Williamson, Kamp and Partee in the 90’s and Keefe in the 00’s—up to Sauerland in the present decade, the objection continues to be run that fuzzy logic based theories of vagueness are incompatible with ordinary usage of compound propositions in the presence of borderline cases. These arguments against fuzzy theories have been rebutted several times but evidently not put to rest. I attempt to do so in this paper
  •  61
    Frege's judgement stroke
    Australasian Journal of Philosophy 78 (2). 2000.
    This paper brings to light a new puzzle for Frege interpretation, and offers a solution to that puzzle. The puzzle concerns Frege’s judgement-stroke (‘|’), and consists in a tension between three of Frege’s claims. First, Frege vehemently maintains that psychological considerations should have no place in logic. Second, Frege regards the judgementstroke—and the associated dissociation of assertoric force from content, of the act of judgement from the subject matter about which judgement is made—…Read more
  •  52
    Book Information Travels in Four Dimensions: The Enigmas of Space and Time. Travels in Four Dimensions: The Enigmas of Space and Time Robin Le Poidevin , Oxford : Clarendon Press , 2003 , xvii + 275 , £14.99 ( cloth ); £8.99 ( paper ) By Robin Le Poidevin. Clarendon Press. Oxford. Pp. xvii + 275. £14.99 (cloth:); £8.99 (paper:).
  •  51
    (No abstract is available for this citation)
  •  38
    In the context of classical (crisp, precise) sets, there is a familiar connection between the notions of counting, ordering and cardinality. When it comes to vague collections, the connection has not been kept in central focus: there have been numerous proposals regarding the cardinality of vague collections, but these proposals have tended to be discussed in isolation from issues of counting and ordering. My main concern in this paper is to draw focus back onto the connection between …Read more
  •  37
    This paper presents a new solution to the problems for orthodox decision theory posed by the Pasadena game and its relatives. I argue that a key question raised by consideration of these gambles is whether evaluative compositionality (as I term it) is a requirement of rationality: is the value that an ideally rational agent places on a gamble determined by the values that she places on its possible outcomes, together with their mode of composition into the gamble (i.e. the probabilities assigned…Read more
  •  36
    Consonance and Dissonance in Solutions to the Sorites
    In Otavio Bueno & Ali Abasnezhad (eds.), On the Sorites Paradox, Springer. forthcoming.
    A requirement on any theory of vagueness is that it solve the sorites paradox. It is generally agreed that there are two aspects to such a solution: one task is to locate the error in the sorites argument; the second task is to explain why the sorites reasoning is a paradox rather than a simple mistake. I argue for a further constraint on approaches to the second task: they should conform to the standard modus operandi in formal semantics, in which the semantic theory one develops is t…Read more
  •  33
    I have argued for a picture of decision theory centred on the principle of Rationally Negligible Probabilities. Isaacs argues against this picture on the grounds that it has an untenable implication. I first examine whether my view really has this implication; this involves a discussion of the legitimacy or otherwise of infinite decisions. I then examine whether the implication is really undesirable and conclude that it is not