•  191
    Freedom and the Fixity of the Past
    Philosophical Review 121 (2): 179-207. 2012.
    According to the Principle of the Fixity of the Past (FP), no one can now do anything that would require the past to have unfolded differently than it actually did, for the past is fixed, over and done with. Why might doing something in the future require the past to be different? Because if determinism is true—if the laws of nature and the initial conditions of the Big Bang determined a unique future for our universe—then doing anything other than what you are determined to do would require one…Read more
  •  159
    Moorean Phenomena in Epistemic Logic
    In Lev Dmitrievich Beklemishev, Valentin Goranko & Valentin Shehtman (eds.), Advances in Modal Logic 8, College Publications. pp. 178-199. 1998.
    A well-known open problem in epistemic logic is to give a syntactic characterization of the successful formulas. Semantically, a formula is successful if and only if for any pointed model where it is true, it remains true after deleting all points where the formula was false. The classic example of a formula that is not successful in this sense is the “Moore sentence” p ∧ ¬BOXp, read as “p is true but you do not know p.” Not only is the Moore sentence unsuccessful, it is self-refuting, for it ne…Read more
  •  29
    Locales, Nuclei, and Dragalin Frames
    with Guram Bezhanishvili
    In Lev Beklemishev, Stéphane Demri & András Máté (eds.), Advances in Modal Logic, Volume 11, Csli Publications. pp. 177-196. 2016.
    It is a classic result in lattice theory that a poset is a complete lattice iff it can be realized as fixpoints of a closure operator on a powerset. Dragalin [9,10] observed that a poset is a locale (complete Heyting algebra) iff it can be realized as fixpoints of a nucleus on the locale of upsets of a poset. He also showed how to generate a nucleus on upsets by adding a structure of “paths” to a poset, forming what we call a Dragalin frame. This allowed Dragalin to introduce a semantics for int…Read more
  •  79
    Response to Egré and Xu
    In Johan van Benthem Fenrong Liu (ed.), Logic Across the University: Foundations and Applications, College Publications. pp. 39-46. 2013.
    In this note, I respond to comments by Paul Egré and Xu Zhaoqing on my “Epistemic Closure and Epistemic Logic I: Relevant Alternatives and Subjunctivism” (Journal of Philosophical Logic).
  •  48
    A bimodal perspective on possibility semantics
    with Johan van Benthem and Nick Bezhanishvili
    Journal of Logic and Computation 27 (5). 2017.
    In this article, we develop a bimodal perspective on possibility semantics, a framework allowing partiality of states that provides an alternative modelling for classical propositional and modal logics. In particular, we define a full and faithful translation of the basic modal logic K over possibility models into a bimodal logic of partial functions over partial orders, and we show how to modulate this analysis by varying across logics and model classes that have independent topological motivat…Read more
  •  200
    Fallibilism and Multiple Paths to Knowledge
    Oxford Studies in Epistemology 5 97-144. 2015.
    This chapter argues that epistemologists should replace a “standard alternatives” picture of knowledge, assumed by many fallibilist theories of knowledge, with a new “multipath” picture of knowledge. The chapter first identifies a problem for the standard picture: fallibilists working with this picture cannot maintain even the most uncontroversial epistemic closure principles without making extreme assumptions about the ability of humans to know empirical truths without empirical investigation. …Read more