Ontology without Axioms.- Le?niewski’s Analysis of Russell’s Paradox.- Logic and Existence.- Le?niewski’s Calculus of Names.- On Le?niewski’s Ontology.- Ontology: Lesniewski’s Logical Language.- On Le?niewski’s Elementary Ontology.- Studies in Le?niewski’s Mereology.- On the Definition of Mereological Class.- Consistency of Le?niewski’s Mereology.- The Dependence of a Mereological Axiom.- Relation of Le?niewski’s Mereology to Boolean Algebra.- Index of Names.