Title: Subminimal negation based on a class of absurdities Abstract: In this talk we will discuss several approaches to add a negation to the positive part of the intuitionistic propositional logic, like minimal negation and subminimal negations. One such logic is the propositional contraposition logic, CoPC, which has as its only axiom for negation (p -> q)-> (-q -> -p). For this logic two different types of semantics are known. One is a neighborhood semantics, the other, surprisingly, a generalization of the semantics for minimal logic, using, instead of one ‘absurdum’, a class of absurdities. We will point out the relationship between the two semantics and briefly discuss the arithmetic based on contraposition logic.