Strict embedding of the elementary ontology into the monadic second-order calculus of predicates admitting the empty individual domain

Abstract

There is given the proof of strict embedding of Leśniewski's elementary ontology into monadic second-order calculus of predicates providing a formalization of the class of all formulas valid in all domains (including the empty one). The elementary ontology with the axiom ∃ S (S ɛ S) is strictly embeddable into monadic second-order calculus of predicates which provides a formalization of the classes of all formulas valid in all non-empty domains.