Identity and Discernibility in Philosophy and Logic

J.A.C Ladyman, Øystein Linnebo, R.G Pettigrew

Research output: Contribution to journalArticle (Academic Journal)peer-review

28 Citations (Scopus)


Questions about the relation between identity and discernibility are important both in philosophy and in model theory. We show how a philosophical question about identity and discernibility can be ‘factorized’ into a philosophical question about the adequacy of a formal language to the description of the world, and a mathematical question about discernibility in this language. We provide formal definitions of various notions of discernibility and offer a complete classification of their logical relations. Some new and surprising facts are proved; for instance, that weak discernibility corresponds to discernibility in a language with constants for every object, and that weak discernibility is the most discerning nontrivial discernibility relation.
Translated title of the contributionIdentity and Indiscernibility in Philosophy and Logic
Original languageEnglish
Pages (from-to)162 - 186
Number of pages25
JournalReview of Symbolic Logic
Issue number1
Early online date17 Nov 2011
Publication statusPublished - Mar 2012

Structured keywords

  • Centre for Science and Philosophy


  • identity
  • discernibility
  • philosophy
  • logic


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