Publications

I'm a philosophical logician. I build non-classical systems and put them to work, in technical settings and in everyday life. In paraconsistent logic, I ask how a logical system can accommodate contradictions, and I do the meta-theory paraconsistently rather than falling back on classical reasoning. In ceteris paribus logic, I give a formal account of 'all other things being equal' reasoning. In dynamic logic, I look at how beliefs and preferences shift through interaction within a group. More recently I've been working at the meeting of formal logic and critical theory, asking how logic operates in communities and who it leaves out. Both my books come from this.

If you have trouble getting hold of any of my papers, email me.

  • Logic is often taken to be a neutral space of reasoning. But neutrality doesn't guarantee equality, let alone equity. The gap is where I've identified logical injustice: dismissing someone's reasoning as incoherent when the fault lies with the standards being applied. This work started with a paper on feminist critiques of critical thinking and now runs through both my books.

    1. Girard, Patrick. A Logician's Code of Conduct. Montreal: McGill-Queen's University Press, 2026.

    2. Girard, Patrick. Logic in the Wild. Montreal: McGill-Queen's University Press, 2024.

    3. Girard, Patrick, Adam Dalgleish, and Maree Davies. "Critical Thinking, Bias and Feminist Philosophy: Building a Better Framework through Collaboration." Informal Logic 37, no. 4 (2017): 351-369. https://doi.org/10.22329/il.v37i4.4794

  • I want to take paraconsistent logic to the next level. Not just a toy logic that accommodates eccentricities, but a meta-theory that does foundational work for logic, mathematics, and everyday reasoning. The 2017 special issue below came out of a conference I organised with Maarten McKubre-Jordens and Zach Weber.

    I'm The Modal Madman in the Logician’s Liberation League.

    1. Girard, Patrick, and Koji Tanaka. "Against Classical Paraconsistent Metatheory." Analysis 83, no. 2 (2023): 285–94. https://doi.org/10.1093/analys/anac093

    2. Girard, Patrick, Guillermo Badia, and Zach Weber. "Paraconsistent Metatheory: New Proofs with Old Tools." Journal of Philosophical Logic 51 (2022): 825–856. https://doi.org/10.1007/s10992-022-09651-x

    3. Girard, Patrick, and Zach Weber. "Modal Logic Without Contraction in a Metatheory Without Contraction." The Review of Symbolic Logic 12, no. 4 (2019): 685-701. https://doi.org/10.1017/S1755020319000030

    4. Girard, Patrick. "Dialetheic Conditional Modal Logic." In Graham Priest on Dialetheism and Paraconsistency, edited by Can Başkent and Thomas Macaulay Ferguson, 18:271–84. Cham: Springer International Publishing, 2019. https://doi.org/10.1007/978-3-030-25365-3_14

    5. Girard, Patrick, Maarten McKubre-Jordens, and Zach Weber. Non-Classicality: Logic, Mathematics, Philosophy. Special Issue of The Australasian Journal of Logic 14, no. 1 (2017).

    6. Girard, Patrick, Guillermo Badia, and Zach Weber. "What is an Inconsistent Truth Table." Australasian Journal of Philosophy 94, no. 3 (2016): 533-548. https://doi.org/10.1080/00048402.2015.1093010

    7. Girard, Patrick, and Zach Weber. "Bad Worlds." Thought: A Journal of Philosophy 4, no. 2 (2015): 93-101. https://doi.org/10.1002/tht3.162

  • Ceteris paribus clauses are everywhere in philosophy, economics, and the social sciences, and they're usually left vague. I've developed a modal logic that makes them precise: which factors are held fixed, which vary, and what follows.

    1. Girard, Patrick, and Marcus A. Triplett. "Prioritised Ceteris Paribus Logic for Counterfactual Reasoning." Synthese 195, no. 4 (2018): 1681-1703. https://doi.org/10.1007/s11229-016-1296-5

    2. Girard, Patrick, and Marcus Anthony Triplett. "Ceteris Paribus Logic in Counterfactual Reasoning." In Proceedings of the 15th Conference on Theoretical Aspects of Rationality and Knowledge, 2015. https://doi.org/10.48550/arXiv.1606.07522

    3. Girard, Patrick, and Jeremy Seligman. "Flexibility in Ceteris Paribus Reasoning." The Australasian Journal of Logic 10 (2011): 67-99. https://doi.org/10.26686/ajl.v10i0.1826

    4. Girard, Patrick, Johan van Benthem, and Olivier Roy. "Everything Else Being Equal: A Modal Logic for Ceteris Paribus Preferences." Journal of Philosophical Logic 38, no. 1 (2009): 83-125. https://doi.org/10.1007/s10992-008-9085-3

    • Selected for The Philosopher's Annual 2009, republished in Grim, P., Charlow, N., Gallow, D., and Herold, D. (eds), The Philosopher's Annual.

  • Beliefs and preferences don't sit still. They shift as information arrives and as people talk to each other. I use dynamic logic to model that: how a belief gets revised when new information contradicts it, how preferences aggregate, and how the shape of a community affects what it comes to know. Dynamic Formal Epistemology below came out of a conference I organised with Olivier Roy and Mathieu Marion.

    1. Girard, Patrick. "Logic of Promotion and Demotion." In The Cognitive Foundations of Group Attitudes and Social Interaction, edited by Andreas Herzig and Emiliano Lorini, 107-120. Springer, 2015. https://doi.org/10.1007/978-3-319-21732-1_5

    2. Girard, Patrick, Liu Fenrong, and Jeremy Seligman. "Logical Dynamics of Belief Change in the Community." Synthese 191, no. 11 (2014): 2403–31. https://doi.org/10.1007/s11229-014-0432-3

    3. Girard, Patrick, Liu Fenrong, and Jeremy Seligman. "Facebook and the Epistemic Logic of Friendship." In TARK 2013 - Proceedings of the 14th Conference on Theoretical Aspects of Rationality and Knowledge, edited by Burkhard Schipper, 2013. https://doi.org/10.48550/arXiv.1310.6440

    4. Girard, Patrick, Liu Fenrong, and Jeremy Seligman. "Knowledge, Friendship and Social Announcements." In Logic Across the University: Foundations and Applications: Proceedings of the Tsinghua Logic Conference, Beijing, 2013, edited by Johan van Benthem and Fenrong Liu. London, UK: College Publications, 2013.

    5. Girard, Patrick, Liu Fenrong, and Jeremy Seligman. "General Dynamic Dynamic Logic." In Advances in Modal Logic: Volume 9, edited by Thomas Bolander, Torben Braüner, Silvio Ghilardi, and Lawrence Moss, 239-260. London, UK: College Publications, 2012. http://www.aiml.net/volumes/volume9/Girard-Seligman-Liu.pdf

    6. Girard, Patrick. "Modal Logic for Lexicographic Preference Aggregation." In Games, Norms and Reasons, edited by Johan van Benthem, Amitabha Gupta, and Eric Pacuit, 97-117. Springer Verlag, 2011. https://doi.org/10.1007/978-94-007-0714-6_6

    7. Girard, Patrick, Liu Fenrong, and Jeremy Seligman. "Logic in the Community." Proceedings of the Fourth Indian Conference in Logic and Applications, 178-188, 2011. https://doi.org/10.1007/978-3-642-18026-2_15

    8. Girard, Patrick, Olivier Roy, and Mathieu Marion. Dynamic Formal Epistemology. Synthese Library 351. Dordrecht: Springer, 2011. https://doi.org/10.1007/978-94-007-0074-1

    9. Girard, Patrick, and Jeremy Seligman. "An Analytic Logic of Aggregation." In Logic and Its Applications, Chennai, 146-161, 2009. https://doi.org/10.1007/978-3-540-92701-3_10

  • How should you change your mind when new evidence cuts against what you already believe? I work on this with dynamic epistemic logic, which models belief change as an operation rather than a state. Some of it asks what happens when the beliefs being revised are themselves contradictory.

    1. Girard, Patrick, and Koji Tanaka. "Paraconsistent Dynamics." Synthese 193, no. 1 (2016): 1-14. https://doi.org/10.1007/s11229-015-0740-2

    2. Girard, Patrick, and Hans Rott. "Belief Revision and Dynamic Logic." In Johan Van Benthem on Logic and Information Dynamics, edited by Alexandru Baltag and Sonja Smets, 203-233. Springer, 2014. https://doi.org/10.1007/978-3-319-06025-5_8

    3. Girard, Patrick. "From Onions to Broccoli: Generalizing Lewis' Counterfactual Logic." Journal of Applied Non-Classical Logic 17, no. 2 (2007): 213-229. https://doi.org/10.3166/jancl.17.213-229

  • Metaphysics isn't my home ground, but logical questions turn up there constantly and I'm happy to be brought in when they do. Both papers below came out of collaborations of that kind.

    1. Girard, Patrick, Rohan French, and Dave Ripley. "Classical Counterpossibles." The Review of Symbolic Logic (2020): 1-17. https://doi.org/10.1017/S1755020319000637

    2. Girard, Patrick, and Luca Moretti. "Antirealism and the Conditional Fallacy: The Semantic Approach." Journal of Philosophical Logic 43, no. 4 (2014): 761-783. https://doi.org/10.1007/s10992-013-9288-0

  • I work on how critical thinking gets taught, and on making logic teachable to people the standard methods leave out.

    Girard, Patrick, Maree Davies, and Simon Esling. "Street Smarts: A Developing Critical Thinking Talk Framework for Adolescents." In Dialogic Pedagogy: Discourse in Contexts from Pre-School to University, edited by Anne Thwaite, Alyson Simpson, and Pauline Jones. Routledge Research in Education. London and New York: Routledge, 2023.

    Textbook: the Auckland Remix of forall x

    With Andrew Withy and Jeremy Seligman, I adapted forall x, the Open Logic Project's open-source formal logic textbook, for students at the University of Auckland. It covers truth-functional propositional logic, first-order predicate logic with identity, and Fitch-style natural deduction, with examples rewritten for an Auckland audience.

    Download the Auckland Remix PDF

    Teaching logic to blind students

    With my late friend and colleague Jonathan McKeown-Green, I developed a method for teaching logic to visually impaired students using Polish notation.

    Girard, Patrick, and Jonathan McKeown-Green. "Teaching Logic to Blind Students." https://philpapers.org/rec/GIRTLT