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Professor Susanne Bobzien

MA, DPhil, FBA
Senior Research Fellow since 2013
Professor of Philosophy, University of Oxford
I have currently three main research interests, two in ancient logic, one in contemporary philosophy. First, I aim to improve our understanding of Stoic logic by bringing out similarities and dissimilarities to contemporary logic. Thus comparison of Stoic sequent logic with contemporary proof theory shows the Stoic system to be an unusual Gentzen-style relevance logic with backward proof search; comparison with contemporary first-order logic suggests Stoic logic contains the elements required for a theory of multiple generality with a variable-free syntax; comparison with Frege’s philosophical work indicates a wide-ranging dependency on the Stoics. The second, more historical, project traces hypothetical syllogistic from Aristotle to Boethius. My main contemporary interest is in vagueness and the Sorites paradox. I argue that the Kripke-complete normal first-order modal logic QS4M+BF+FIN holds the key to a generic solution for the Sorites. To this end, I have introduced the notions of columnar higher-order vagueness, semi-determinability and borderline nestings. An empirically based combination of contextualism and assessment sensitivity is central to the solution and the theory of vagueness that comes with it. Other interests include the semantic paradoxes and determinism, freedom, and moral responsibility.
Contact: susanne.bobzien at
Professor Susanne Bobzien
  • Background

    • Senior Research Fellow, All Souls College (from 2013)
    • Professor of Philosophy, then Senior Research Scholar (since 2010), Yale University (from 2002 to 2013)
    • CUF Lecturer in Philosophy, University of Oxford (from 1993 to 2002)
    • Official Fellow and Praelector in Philosophy, The Queen’s College, Oxford (from 1990 to 2002)
    • Tutor and Fellow in Philosophy, Balliol College, Oxford (from 1989 to 1990)
    • Postgraduate at University of Oxford (from 1987 to 1993)
  • Research interests

    • Ancient philosophy
    • History of logic
    • Vagueness and the Sorites
    • Determinism, freedom, and moral responsibility
    • Philosophical logic
    • Philosophy of language
    • Philosophy of logic
  • Selected publications

    • Frege plagiarized the Stoics, in F. Leigh (ed.) Forms, Language, and Education: The Keeling Lectures in Ancient Philosophy 2011-18, London: Wiley, 2020.
    • A generic solution to the Sorites paradox based on the normal modal logic QS4M+BF+FIN, in A. Abasnezhad / O. Bueno (eds), The Sorites Paradox: New Essays, New York: Springer, 2020.
    • Demonstration and the indemonstrability of the Stoic indemonstrables, Phronesis 2020.
    • Stoic sequent logic and proof theory, Journal of the History and Philosophy of Logic 40, 2019, 234-265.
    • Gestalt Shifts in the Liar, in B. Armour-Garb (ed.) Reflections on the Liar, Oxford University Press, 2017, 71-113.
    • Columnar Higher-order Vagueness or Vagueness is Higher-Order Vagueness, Aristotelian Society Supplementary Volume 89, 2015, 61-87
    • Found in Translation: Aristotle’s Nicomachean Ethics 3. 5, 1113b7-8 and its Reception, Oxford Studies in Ancient Philosophy 45, 2013, 103-148.
    • Publications (External Link)
  • Other professional memberships and roles

    • Member, Institute for Advanced Study, Princeton (2008-9)
    • Member of the Advisory or Editorial Boards for: Journal of the History of Philosophy; Oxford Studies in Ancient Philosophy; Revue de Philosophie Ancienne; British Journal for the History of Philosophy; History and Philosophy of Logic; Ancient Philosophy; Rhizomata: A Journal for Ancient Philosophy and Science; Open Philosophy; Thought: A Journal of Philosophy (Editorial Panel)