Professor of Philosophy, New York University
Address: 5 Washington Place, New York, NY 10003.

Cian Dorr


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  • The Bounds of Possibility: Puzzles of Modal Variation (with John Hawthorne and Juhani Yli-Vakkuri) [New: October 2021]

    Oxford: Oxford University Press, 2021.

    In general, a given object could have been different in certain respects. For example, the Great Pyramid could have been somewhat shorter or taller; the Mona Lisa could have had a somewhat different pattern of colours; an ordinary table could have been made of a somewhat different quantity of wood. But there seem to be limits. It would be odd to suppose that the Great Pyramid could have been thimble-sized; that the Mona Lisa could have had the pattern of colours that actually characterizes The Scream; or that the table could have been made of the very quantity of wood that in fact made some other table. However, there are puzzling arguments that purport to show that so long as an object is capable of being somewhat different in some respect, it is capable of being radically different in that respect. These arguments rely on two tempting thoughts: first, that an object’s capacity for moderate variation is a non-contingent matter, and second, that what is possibly possible is simply possible. This book systematically investigates competing strategies for resolving these puzzles, and defends one of them. Along the way it engages with foundational questions about the metaphysics of modality

Published and forthcoming articles
  • Classicism (with Andrew Bacon) [New: December 2021]

    Forthcoming in Higher-Order Metaphysics, ed. Peter Fritz and Nicholas K. Jones. Oxford University Press.

    We explore a theory we call ‘Classicism’, whose guiding idea is that provable coextensiveness in classical higher-order logic is sufficient for identity.

  • Consequences of Comparability (with Jacob M. Nebel and Jake Zuehl) [New: October 2021]

    Philosophical Perspectives 35 (2021): 70–98.

    We defend three controversial claims about preference, credence, and choice. First, all agents (not just rational ones) have complete preferences. Second, all agents (again, not just rational ones) have real-valued credences in every proposition in which they are confident to any degree. Third, there is almost always some unique thing we ought to do, want, or believe.

  • The Case for Comparability (with Jacob M. Nebel and Jake Zuehl) [New: October 2021]

    Forthcoming in Noûs.

    We argue that all comparative expressions in natural language obey a principle that we call Comparability: if x and y are at least as F as themselves, then either x is at least as F as y or y is at least as F as x. This principle has been widely rejected among philosophers, especially by ethicists, and its falsity has been claimed to have important normative implications. We argue that Comparability is needed to explain the goodness of several patterns of inference that seem manifestly valid, that the purported failures of Comparability would have absurd consequences, and that the influential arguments against Comparability are less compelling than they may have initially seemed.

  • Solving a Paradox of Evidential Equivalence (with John Hawthorne and Yoaav Isaacs)

    Mind 130.520 (2021): 1159–82.

    David Builes presents a paradox concerning how confident you should be that any given member of an infinite collection of fair coins landed heads, conditional on the information that they were all flipped and only finitely many of them landed heads. We argue that if you should have any conditional credence at all, it should be 1/2.

  • Diamonds Are Forever (with Jeremy Goodman)

    Noûs54.3 (2020): 632–65.

    We defend the thesis that every necessarily true proposition is always true. Since not every proposition that is always true is necessarily true, our thesis is at odds with theories of modality and time, such as those of David Kaplan and Kit Fine, which posit a fundamental symmetry between modal and tense operators. According to such theories, just as it is a contingent matter what is true at a given time, it is likewise a temporary matter what is true at a given possible world; so a proposition that is now true at all worlds, and thus necessarily true, may yet at some past or future time be false in the actual world, and thus not always true. We reconstruct and criticise several lines of argument in favour of such a picture, and argue against it on the grounds that such a picture is inconsistent with certain sorts of contingency in the structure of time.

  • Self-Locating Priors and Cosmological Measures (with Frank Arntzenius)

    In The Philosophy of Cosmology, ed. Khalil Chamcham, John Barrow, Simon Saunders, and Joe Silk. Cambridge University Press, 2017.

    We develop a Bayesian framework for thinking about the way evidence about the here and now can bear on hypotheses about the qualitative character of the world as a whole, including hypotheses according to which the total population of the world is infinite. We show how this framework makes sense of the practice cosmologists have recently adopted in their reasoning about such hypotheses.

  • To Be F Is To Be G

    Philosophical Perspectives 30 (2016): 39--134.

    This paper is an investigation of the general logic of "identifications", claims such as 'To be a vixen is to be a female fox', 'To be human is to be a rational animal', and 'To be just is to help one's friends and harm one's enemies', many of which are of great importance to philosophers. I advocate understanding such claims as expressing higher-order identity, and discuss a variety of different general laws which they might be thought to obey.

  • Against Counterfactual Miracles

    Philosophical Review 125 (2016): 241–86.

    This paper considers how counterfactuals should be evaluated on the assumption that determinism is true. I argue against Lewis's influential view that then the actual laws of nature would have been false if something had happened that never actually happened, and in favour of the competing view that history would have been different all the way back. I argue that we can do adequate justice to our ordinary practice of relying on a wide range of historical truths in evaluating counterfactuals by saying that, in typical cases, history would have been only very slightly different until shortly before the relevant time. The paper also draws some connections between the puzzle about counterfactuals under determinism and the debate about whether determinism is consistent with people having unexercised abilities.

  • How Vagueness Could Cut Out at Any Order

    Review of Symbolic Logic 8 (2015): 1–10.

    Timothy Williamson has shown that the B axiom for 'definitely' (α → Δ¬Δ¬α) guarantees that if a sentence is second-order vague in a Kripke model, it is nth order vague for every n. More recently, Anna Mahtani has argued that Williamson's epistemicist theory of vagueness does not support the B axiom, and conjectured that if we consider models in which the “radius of accessibility” varies between different points, we will be able to find sentences that are nth-order vague but (n+1)th-order precise, for any n. This paper bolsters Mahtani's argument, shows her conjecture to be true, and shows that imposing certain further natural constraints on "variable radius" models does not change the situation.

  • Quantifier Variance and the Collapse Theorems

    The Monist 97 (2014): 503-70.

    Quantifier variantists hold that certain relatively minor differences in use, involving differences in our dispositions with respect to certain "ontological" questions, would affect the meanings of the quantifiers in such a way that whichever answers to those questions we were disposed to accept would be true in our mouths. In his 1980 paper 'What's So Logical About the "Logical" Axioms', J. H. Harris proved some theorems which have been widely taken to support the claim that the meanings of all logical constants, including the quantifiers, are uniquely pinned down by certain very general and counterfactually robust facts about how we use them. This paper attempts to get clear on the assumptions required to get from the relevant theorems to this claim of semantic stability, with a view to seeing whether the theorems provide the basis for a non-question-begging argument against quantifier variantism.

  • Semantic Plasticity and Speech Reports (with John Hawthorne)

    Philosophical Review 123 (2014): 281-338.

    Most of the meanings we express belong to large families of variant meanings, among which it would be implausible to suppose that some are much more apt for being expressed than others. This abundance of candidate meanings creates pressure to think that the proposition attributing any particular meaning to an expression is modally plastic: its truth depends very sensitively on the exact microphysical state of the world. However, such plasticity seems to threaten ordinary counterfactuals whose consequents contain speech reports, since it is hard to see how we could reasonably be confident in a counterfactual whose consequent can only be true if a certain very finely-tuned microphysical configuration obtains. In this paper, we develop the foregoing puzzle and explore several possible solutions. tails.

  • Transparency and the Context-Sensitivity of Attitude Reports

    In Empty Representations: Reference and Non-existence, ed. Manuel Garcia-Carpintero and Genoveva Martí (Oxford University Press, 2014): 25–66.

    This paper defends the claim that although ‘Superman is Clark Kent and some people who believe that Superman flies do not believe that Clark Kent flies’ is a logically inconsistent sentence, we can still utter this sentence, while speaking literally, without asserting anything false. The key idea is that the context-sensitivity of attitude reports can be, and often is, resolved in different ways within a single sentence.

  • Knowing Against the Odds (with Jeremy Goodman and John Hawthorne)

    Philosophical Studies 170 (2014):277-87.

    We present and discuss a counterexample to the following plausible principle: if you know that a coin is fair, and for all you know it is going to be flipped, then for all you know it will land tails.

  • Embedding Epistemic Modals (with John Hawthorne)

    Mind 122 (2013): 867–913. (Appeared May 2014)

    Seth Yalcin has pointed out some puzzling facts about the behaviour of epistemic modals in certain embedded contexts. For example, conditionals that begin ‘If it is raining and it might not be raining, …’ sound unacceptable, unlike conditionals that begin ‘If it is raining and I don’t know it, …’. These facts pose a prima facie problem for an orthodox treatment of epistemic modals, according to which they express propositions about the knowledge of some contextually specified individual or group. This paper develops an explanation of the puzzling facts about embedding within an orthodox framework, using broadly Gricean resources.

  • Naturalness (with John Hawthorne)

    In Oxford Studies in Metaphysics vol. 8, ed. Karen Bennett and Dean Zimmerman (Oxford University Press, 2013).

    Lewis's notion of a "natural" property has proved divisive: some have taken to the notion with enthusiasm, while others have been sceptical. However, it is far from obvious what the enthusiasts and the sceptics are disagreeing about. This paper attempts to articulate what is at stake in this debate.

  • Calculus as Geometry (with Frank Arntzenius)

    Chapter 8 of Frank Arntzenius, Space, Time and Stuff (Oxford University Press, 2012).

    We attempt to extend the nominalistic project initiated in Hartry Field's Science Without Numbers to modern physical theories based in differential geometry.

  • De Re A Priori Knowledge

    Mind 120 (2011): 939-91.

    Suppose that (1) is true in a certain context:
    (1) Necessarily, whenever one believes that the F is uniquely F if anything is, and x is the F, one believes that x is uniquely F if anything is.
    I argue that almost always, (2) will be true in the same context:
    (2) Necessarily, whenever one knows a priori that the F is uniquely F if anything is, and x is the F, one knows a priori that x is uniquely F if anything is.
    I also argue that many instances of (1) and (2) are true in ordinary contexts, and conclude that a priori knowledge of contingent de re propositions is a common and unmysterious phenomenon. However, because of the pervasive context-sensitivity of propositional attitude ascriptions, the question what it is possible to know a priori of a given object will have very different answers in different contexts.

  • Physical Geometry and Fundamental Metaphysics

    Proceedings of the Aristotelian Society 111 (2011): 135–59.

    I explore some ways in which one might base an account of the fundamental metaphysics of geometry on the mathematical theory of ‘Linear Structures’ developed by Tim Maudlin in ‘Time, Topology and Physical Geometry’. Having considered some of the challenges facing this approach, I develop an alternative approach, according to which the fundamental ontology includes concrete entities structurally isomorphic to scalar fields.

  • The Eternal Coin: A Puzzle about Self-locating Conditional Credence

    Philosophical Perspectives 25 (2010): 189-205.

    The Eternal Coin is a fair coin that has existed forever, and will exist forever, in a region causally isolated from you. It is tossed every day. How confident should you be that the Coin lands heads today, conditional on (i) the hypothesis that it has landed Heads on every past day, or (ii) the hypothesis that it will land Heads on every future day? I argue for the extremely counterintuitive claim that the correct answer to both questions is 1.

  • Of Numbers and Electrons

    Proceedings of the Aristotelian Society 110 (2010): 133-181.

    According to a tradition stemming from Quine and Putnam, certain theories that entail the existence of mathematical entities are better, qua explanations of our evidence, than any theories that do not, and thus we have the same broadly inductive reason for believing in numbers as we have for believing in electrons. In this paper I consider how the existence of nominalistic modal theories of the form 'Possibly, the concrete world is just as it in fact is and T' and 'Necessarily, if standard mathematics is true and the concrete world is just as it in fact is, then T' bears on this claim. I conclude that, while analogies with theories that attempt to eliminate unobservable concrete entities provide good reason to regard theories of the former kind as explanatorily bad, this reason does not apply to theories of the latter kind, which are not relevantly analogous to anything available to eliminativists about electrons.

  • Iterating Definiteness

    In Cuts and Clouds: Vagueness, its Nature and its Logic, ed. Richard Dietz and Sebastiano Moruzzi. Oxford: Oxford University Press, 2010, pp. 550-575.

    The conclusion of this chapter is that higher-order vagueness is universal: no sentence whatsoever is definitely true, definitely definitely true, definitely definitely definitely true, and so on ad infinitum. The argument, of which there are several versions, turns on the existence of Sorites sequences of possible worlds connecting the actual world to possible worlds where a given sentence is used in such a way that its meaning is very different. The chapter attempts to be neutral between competing accounts of the nature of vagueness and definiteness.

  • There Are No Abstract Objects

    In Contemporary Debates in Metaphysics, ed. John Hawthorne, Theodore Sider and Dean Zimmerman. Malden, MA: Blackwell, 2007.

    I explicate and defend the claim that, fundamentally speaking, there are no numbers, sets, properties or relations. The clarification consists in some remarks on the relevant sense of ‘fundamentally speaking’ and the contrasting sense of ‘superficially speaking’. The defence consists in an attempt to rebut two arguments for the existence of such entities. The first is a version of the indispensability argument, which purports to show that certain mathematical entities are required for good scientific explanations. The second is a speculative reconstruction of Armstrong’s version of the One Over Many argument, which purports to show that properties and relations are required for good philosophical explanations, e.g. of what it is for one thing to be a duplicate of another.

  • What We Disagree About When We Disagree About Ontology

    In Fictionalism in Metaphysics, ed. Mark Kalderon. Oxford: Oxford University Press, 2005.

    In this paper I attempt two things. First, I argue that one can coherently imagine different communities using languages structurally similar to English, but in which the meanings of the quantifiers vary, so that the answers to ontological questions, such as ‘Under what circumstances do some things compose something?’, are different. Second, I argue that nevertheless, one can make sense of the idea that of the various possible assignments of meanings to the quantifiers, one is especially fundamental, so that there is still room for genuine debate as regards the answers to ontological questions construed in the fundamental way. My attempt to explain what is distinctive about the fundamental senses of the quantifiers involves a generalisation of the idea that claims of existence are never analytic.

  • Propositions and Counterpart Theory

    Analysis 65 (2005): 210-18.

    I argue that there is a conflict between two positions defended by David Lewis: counterpart theory, and the identification of propositions with sets of possible worlds. There is no adequate answer to the question whether a world where Humphrey has one winning and one losing counterpart is or is not a member of the set that is the proposition that Humphrey wins. If one says it is, it will follow that it is possible for that proposition to be true without Humphrey winning; if one says that it is not, it will follow that it is possible for Humphrey to win without that proposition being true.

  • Non-Symmetric Relations

    In Oxford Studies in Metaphysics, vol. 1, ed. Dean Zimmerman (Clarendon Press: Oxford, 2004): 155-192.

    Presupposing that most predicates do not correspond directly to genuine relations, I argue that all genuine relations are symmetric. My main argument depends on the premise that there are no brute necessities, interpreted so as to require logical and metaphysical necessity to coincide for sentences composed entirely of logical vocabulary and primitive predicates. Given this premise, any set of purportedly primitive predicates by which one might hope to express the facts about non-symmetric relations order their relata will generate an objectionable multiplication of possibilities. In the final section I give a different argument, based on the weaker premise that brute necessities should not be multiplied without necessity.

  • Vagueness Without Ignorance

    In Philosophical Perspectives 17: Language and Philosophical Linguistics, ed. John Hawthorne and Dean Zimmerman, Blackwell, 2003: 83-114.

    I motivate and briefly sketch a linguistic theory of vagueness, on which the notion of indeterminacy is understood in terms of the conventions of language: a sentence is indeterminate iff the conventions of language either forbid asserting it and forbid asserting its negation, under the circumstances, or permit asserting either. I then consider an objection that purports to show that if this theory (or, as far as I can see, any other theory of vagueness that deserved the label “linguistic”) were true, there would be no such thing as indeterminacy. I respond to this objection by arguing on independent grounds against its main premise, the widely-accepted claim that if it is indeterminate whether P, no human being knows whether P. I defend an alternative view according to which, when it is indeterminate whether P, it is often also indeterminate whether we know that P.

  • Composition as a Fiction (with Gideon Rosen)

    In The Blackwell Guide to Metaphysics, ed. Richard M. Gale. Oxford: Blackwell, 2003.

    We introduce several theories of composition, including Nihilism, according to which there are no composite objects; Universalism, according to which any objects whatsoever compose something; and an intermediate position we attribute to common sense. We argue that neither common sense nor science can give us an adequate reason to rule out any of these theories. We suggest that as long as one cannot rule out the hypothesis that composite objects are much rarer than common sense takes them to be, one should adopt a policy of regulating one's talk and verbalised thought in accordance with the fiction that common sense is right about composition.

    Disclaimer: I'm not sure if I ever believed the claim made in this paper, that ordinary people hold some composition-related views for which they lack good reason. At any rate, I no longer believe this.

  • Sleeping Beauty: In Defence of Elga

    Analysis 62 (2002): 292-295.

    I argue for the “thirder” solution to the Sleeping Beauty puzzle. The argument turns on an analogy with a variant case, in which a coin-toss on Monday night determines whether one's memories of Monday are permanently erased, or merely suspended in such a way that they will return some time after one wakes up on Tuesday.

  • Non-cognitivism and Wishful Thinking

    Noûs 36 (2002): 97-103.

    Even if non-cognitivists about some subject-matter can meet Geach’s challenge to explain how there can be valid implications involving sentences which express non-cognitive attitudes, they face a further problem. I argue that a non-cognitivist cannot explain how, given a valid argument whose conclusion expresses a belief and at least one of whose premises expresses a non-cognitive attitude, it could be reasonable to infer the conclusion from the premises.

Reviews, discussions, and encyclopedia articles
Unpublished work, not exactly “in progress”
  • How to Be a Modal Realist [Restored from oblivion: October 2019]

    This paper investigates the form a modal realist analysis of possibility and necessity should take. It concludes that according to the best version of modal realism, the notion of a world plays no role in the analysis of modal claims. All contingent claims contain some de re element; the effect of modal operators on these elements is described by a counterpart theory which takes the same form whether the de re reference is to a world or to something else. This fully general counterpart theory can validate orthodox modal logic, including the logic of ‘actually’.

    Note: This paper has grown into a book manuscript, entitled Counterparts, which is under contract with OUP. Despite the flaws in this paper version I am putting it up here since some people have cited it.

  • Finding Ordinary Objects in Some Quantum Worlds [Restored from oblivion: October 2019]

    This paper lays out a novel proposal about the metaphysical foundations of (non-relativistic) quantum mechanics, which has some elements in common with Everett's “Many Worlds” interpretation and some elements in common with Bohm's ”Pilot Wave” interpretation. The view agrees with the Everettians that the quantum wavefunction can be interpreted be interpreted as a complete description of the world in fundamental terms. But it holds that this truth of this description suffices for the existence of an uncountable plurality of “worlds” of ordinary, non-fundamental objects, where each such “world” corresponds to a mapping of points of time to points of configuration space that obeys that Bohmian “Guidance Equation”.

    Note: I never published this paper because I decided it needed to be a book. I would still like to turn it into a book! But I have not yet done so, and since I also have no plans to publish the paper, I'm keeping it up here.

  • A Challenge for Halfers

    A short reply to Roger White’s paper ‘The Generalised Sleeping Beauty Problem: A Challenge for Thirders’. I argue that the mode of reasoning employed by White leads to an implausible view according to which that Beauty's credence in Heads when she wakes up should be near 1/3, unless she is confident that her two wakings will be exactly alike in all evidential respects. I also say how this mode of reasoning should be resisted.

  • Dissertation: The Simplicity of Everything

    Argues that “Strictly and literally speaking, there are no complex entities”. Warning: I am now much less confident than I was when I wrote this dissertation of the power of sentences like this to unambiguously convey the claim I wanted to make.

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