XCB, the Last of the Shortest Single Axioms for the Classical Equivalential Calculus

11/13/2002

∙

by   Larry Wos, et al.

∙

0

∙

share

It has long been an open question whether the formula XCB = EpEEEpqErqr is, with the rules of substitution and detachment, a single axiom for the classical equivalential calculus. This paper answers that question affirmatively, thus completing a search for all such eleven-symbol single axioms that began seventy years ago.