Universiteit Leiden

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Thomas Fossen

University Lecturer Political Philosophy

Dr. T. Fossen
+31 71 527 5244

Thomas Fossen is a University Lecturer at the Institute for Philosophy.

More information about Thomas Fossen

I am assistant professor of political philosophy and director of the Centre for Political Philosophy. I work across a diverse range of topics and philosophical traditions (continental and analytic). I am currently working on questions about academic activism and civil disobedience in the context of the climate crisis.

My book Facing Authority: A Theory of Political Legitimacy is available open access from Oxford University Press (2024). The book examines what is involved in judging the legitimacy of a regime from a practical standpoint, in the face of disagreement and uncertainty. It develops a pragmatist approach to political legitimacy, as an alternative to the predominant moralist and realist approaches in political theory. Drawing on a range of sources, from philosophy of language to phenomenology and critical theory, it examines the role of representations of power, identities, and events in judging legitimacy.

My past work has addressed topics including the concept of representation, agonistic and deliberative theories of democracy, and online Voting Advice Applications. I also have an interest in theoretical methods and approaches and have written on philosophical pragmatism and political realism.

Research interests

  • Climate activism
  • Theories of democracy
  • Political legitimacy
  • Political obligation
  • Political representation
  • Philososophical pragmatism
  • Methods and approaches in political theory


I studied political science and philosophy in Leiden and Berkeley and received my PhD in Philosophy from Utrecht in 2011. I worked as lecturer and postdoc in Utrecht and Leiden before obtaining a permanent position in Leiden (2015). In 2015 I received an NWO Veni personal research grant. I have been a visiting researcher at the University of Chicago, KU Leuven, and the University of Essex. In 2020-2021 I was a member of the Institute for Advanced Study (Princeton) and a fellow at the Forschungskolleg Humanwissenschaften (Goethe University, Frankfurt, with a Humboldt Fellowship for Experienced Researchers).

(Profile photo by Stefanie Wetzel)


University Lecturer Political Philosophy

  • Faculty of Humanities
  • Instituut voor Wijsbegeerte

Work address

P.J. Veth
Nonnensteeg 1-3
2311 VJ Leiden
Room number 2,05



  • No relevant ancillary activities
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