Journal of Philosophical Logic

, Volume 38, Issue 1, pp 83-125

First online:

Everything Else Being Equal: A Modal Logic for Ceteris Paribus Preferences

  • Johan van BenthemAffiliated withInstitute for Logic, Language and Computation, University of AmsterdamStanford University Email author 
  • , Patrick GirardAffiliated withStanford UniversityUniversity of Auckland
  • , Olivier RoyAffiliated withInstitute for Logic, Language and Computation, University of AmsterdamFaculty of Philosophy, University of Groningen

Rent the article at a discount

Rent now

* Final gross prices may vary according to local VAT.

Get Access


This paper presents a new modal logic for ceteris paribus preferences understood in the sense of “all other things being equal”. This reading goes back to the seminal work of Von Wright in the early 1960’s and has returned in computer science in the 1990’s and in more abstract “dependency logics” today. We show how it differs from ceteris paribus as “all other things being normal”, which is used in contexts with preference defeaters. We provide a semantic analysis and several completeness theorems. We show how our system links up with Von Wright’s work, and how it applies to game-theoretic solution concepts, to agenda setting in investigation, and to preference change. We finally consider its relation with infinitary modal logics.


Ceteris paribus Preference logic Modal logic Dynamic logic Philosophy of action Game theory