Suppositions, extensionality, and conditionals

A critique of the mental model theory of Johnson-Laird and Byrne (2002)

Jonathan St B T Evans*, David E. Over, Simon J. Handley

*Corresponding author for this work

Research output: Contribution to journalReview article

100 Citations (Scopus)


P. N. Johnson-Laird and R. M. J. Byrne (2002) proposed an influential theory of conditionals in which mental models represent logical possibilities and inferences are drawn from the extensions of possibilities that are used to represent conditionals. In this article, the authors argue that the extensional semantics underlying this theory is equivalent to that of the material, truth-functional conditional, at least for what they term "basic" conditionals, concerning arbitrary problem content. On the basis of both logical argument and psychological evidence, the authors propose that this approach is fundamentally mistaken and that conditionals must be viewed within a suppositional theory based on what philosophical logicians call the Ramsey test. The Johnson-Laird and Byrne theory is critically examined with respect to its account of basic conditionals, nonbasic conditionals, and counterfactuals.

Original languageEnglish
Pages (from-to)1040-1052
Number of pages13
JournalPsychological Review
Issue number4
Publication statusPublished - Oct 2005
Externally publishedYes

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