 The basic subminimal logic N characterized by the class of all frames can be presented as the extension of the standard axiomatization of positive intuitionistic logic by the congruence axiom scheme \( (A \leftrightarrow B ) \rightarrow (\neg A \leftrightarrow \neg B)\). The validity of that axiom (its truth at every state of every model) is guaranteed by condition (*), but it is not distinctive of negation. The following additional schematic axioms are considered in Colacito, De Jongh, and Vargas 2017: