Reflections on a Proof of Elementarity

Robert Goldblatt

School of Mathematical and Computing Sciences
Victoria University
P.O. Box 600
New Zealand


This is an exposition and analysis of van Benthem's original proof, hitherto unpublished, that if the class of structures (frames) validating a modal formula is closed under elementary equivalence, then it is the class of all models of a single first-order sentence.

Bibtex Entry

Photo taken by Rob Goldblatt in a Tubingen restaurant in December 1977.
From left to right are Jens Erik Fenstad, Johan van Benthem, Dagfinn Follesdal, Ede Zimmermann, Arnim von Stechow, Uwe Monnich, ??