First degree formulas in quantified S5

  • Alasdair Urquhart University of Toronto

Abstract

This note provides a proof that the formula  L(Ex)( Fx   &  ~LFx)  is not equivalent to any first degree formula in the context of the quantified version of the modal logic S5.  This solves a problem posed by Max Cresswell.

 

 

Author Biography

Alasdair Urquhart, University of Toronto

Professor Emeritus

Departments of Philosophy and Computer Science

Published
2015-07-20
How to Cite
URQUHART, Alasdair. First degree formulas in quantified S5. The Australasian Journal of Logic, [S.l.], v. 12, n. 5, july 2015. ISSN 1448-5052. Available at: <https://ojs.victoria.ac.nz/ajl/article/view/3891>. Date accessed: 21 sep. 2019. doi: https://doi.org/10.26686/ajl.v12i5.3891.