Free Choice Impossibility Results


Research output: Journal PublicationsJournal Article (refereed)peer-review

4 Citations (Scopus)


Free Choice is the principle that possibly p or q implies and is implied by possibly p and possibly q. A variety of recent attempts to validate Free Choice rely on a nonclassical semantics for disjunction, where the meaning of p or q is not a set of possible worlds. This paper begins with a battery of impossibility results, showing that some kind of nonclassical semantics for disjunction is required in order to validate Free Choice. The paper then provides a positive account of Free Choice, by identifying a family of dynamic semantics for disjunction that can validate the inference. On all such theories, the meaning of p or q has two parts. First, p or q requires that our information is consistent with each of p and q. Second, p or q narrows down our information by eliminating some worlds. It turns out that this second component of or is well behaved: there is a strongest such meaning that p or q can express, consistent with validating Free Choice. The strongest such meaning is the classical one, on which p or q eliminates any world where both p and q are false. In this way, the classical meaning of disjunction turns out to be intimately related to the validity of Free Choice.
Original languageEnglish
Pages (from-to)249–282
Number of pages34
JournalJournal of Philosophical Logic
Issue number2
Early online date18 Jun 2019
Publication statusPublished - Apr 2020

Bibliographical note

This research was supported by Research Grants Council Grant #23602118.


  • Semantics
  • Free Choice
  • Dynamic semantics
  • Impossibility results
  • Free choice


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